diff --git a/src/consensus/consensus.h b/src/consensus/consensus.h
index 8ee35c47b5..fbe29c5809 100644
--- a/src/consensus/consensus.h
+++ b/src/consensus/consensus.h
@@ -1,53 +1,69 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #ifndef BITCOIN_CONSENSUS_CONSENSUS_H
 #define BITCOIN_CONSENSUS_CONSENSUS_H
 
 #include <cstdint>
 
 /** 1MB */
 static const uint64_t ONE_MEGABYTE = 1000000;
 /** The maximum allowed size for a transaction, in bytes */
 static const uint64_t MAX_TX_SIZE = ONE_MEGABYTE;
 /** The minimum allowed size for a transaction, in bytes */
 static const uint64_t MIN_TX_SIZE = 100;
 /** The maximum allowed size for a block, before the UAHF */
 static const uint64_t LEGACY_MAX_BLOCK_SIZE = ONE_MEGABYTE;
 /** Default setting for maximum allowed size for a block, in bytes */
 static const uint64_t DEFAULT_MAX_BLOCK_SIZE = 32 * ONE_MEGABYTE;
 /**
- * The maximum allowed number of signature check operations per MB in a block
- * (network rule).
+ * The maximum allowed number of parsed signature check operations (SigOps)
+ * per MB in a block (network rule).
  */
 static const int64_t MAX_BLOCK_SIGOPS_PER_MB = 20000;
 /** allowed number of signature check operations per transaction. */
 static const uint64_t MAX_TX_SIGOPS_COUNT = 20000;
+/**
+ * The ratio between the maximum allowable block size and the maximum allowable
+ * SigChecks (executed signature check operations) in the block. (network rule).
+ */
+static const int BLOCK_MAXBYTES_MAXSIGCHECKS_RATIO = 141;
 /**
  * Coinbase transaction outputs can only be spent after this number of new
  * blocks (network rule).
  */
 static const int COINBASE_MATURITY = 100;
 /** Coinbase scripts have their own script size limit. */
 static const int MAX_COINBASE_SCRIPTSIG_SIZE = 100;
 
 /** Flags for nSequence and nLockTime locks */
 /** Interpret sequence numbers as relative lock-time constraints. */
 static constexpr unsigned int LOCKTIME_VERIFY_SEQUENCE = (1 << 0);
 /** Use GetMedianTimePast() instead of nTime for end point timestamp. */
 static constexpr unsigned int LOCKTIME_MEDIAN_TIME_PAST = (1 << 1);
 
 /**
  * Compute the maximum number of sigops operation that can contained in a block
  * given the block size as parameter. It is computed by multiplying
  * MAX_BLOCK_SIGOPS_PER_MB by the size of the block in MB rounded up to the
  * closest integer.
  */
 inline uint64_t GetMaxBlockSigOpsCount(uint64_t blockSize) {
     auto nMbRoundedUp = 1 + ((blockSize - 1) / ONE_MEGABYTE);
     return nMbRoundedUp * MAX_BLOCK_SIGOPS_PER_MB;
 }
 
+/**
+ * Compute the maximum number of sigchecks that can be contained in a block
+ * given the MAXIMUM block size as parameter. The maximum sigchecks scale
+ * linearly with the maximum block size and do not depend on the actual
+ * block size. The returned value is rounded down (there are no fractional
+ * sigchecks so the fractional part is meaningless).
+ */
+inline uint64_t GetMaxBlockSigChecksCount(uint64_t maxBlockSize) {
+    return maxBlockSize / BLOCK_MAXBYTES_MAXSIGCHECKS_RATIO;
+}
+
 #endif // BITCOIN_CONSENSUS_CONSENSUS_H
diff --git a/src/miner.cpp b/src/miner.cpp
index 95dac5ffeb..48a91f0f52 100644
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -1,571 +1,589 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <miner.h>
 
 #include <amount.h>
 #include <chain.h>
 #include <chainparams.h>
 #include <coins.h>
 #include <config.h>
 #include <consensus/activation.h>
 #include <consensus/consensus.h>
 #include <consensus/merkle.h>
 #include <consensus/tx_verify.h>
 #include <consensus/validation.h>
 #include <hash.h>
 #include <net.h>
 #include <policy/policy.h>
 #include <pow.h>
 #include <primitives/transaction.h>
 #include <script/standard.h>
 #include <timedata.h>
 #include <txmempool.h>
 #include <util/moneystr.h>
 #include <util/system.h>
 #include <validation.h>
 #include <validationinterface.h>
 
 #include <algorithm>
 #include <queue>
 #include <utility>
 
 // Unconfirmed transactions in the memory pool often depend on other
 // transactions in the memory pool. When we select transactions from the
 // pool, we select by highest fee rate of a transaction combined with all
 // its ancestors.
 
 uint64_t nLastBlockTx = 0;
 uint64_t nLastBlockSize = 0;
 
 int64_t UpdateTime(CBlockHeader *pblock, const Consensus::Params &params,
                    const CBlockIndex *pindexPrev) {
     int64_t nOldTime = pblock->nTime;
     int64_t nNewTime =
         std::max(pindexPrev->GetMedianTimePast() + 1, GetAdjustedTime());
 
     if (nOldTime < nNewTime) {
         pblock->nTime = nNewTime;
     }
 
     // Updating time can change work required on testnet:
     if (params.fPowAllowMinDifficultyBlocks) {
         pblock->nBits = GetNextWorkRequired(pindexPrev, pblock, params);
     }
 
     return nNewTime - nOldTime;
 }
 
 uint64_t CTxMemPoolModifiedEntry::GetVirtualSizeWithAncestors() const {
     return GetVirtualTransactionSize(nSizeWithAncestors,
                                      nSigOpCountWithAncestors);
 }
 
 BlockAssembler::Options::Options()
     : nExcessiveBlockSize(DEFAULT_MAX_BLOCK_SIZE),
       nMaxGeneratedBlockSize(DEFAULT_MAX_GENERATED_BLOCK_SIZE),
       blockMinFeeRate(DEFAULT_BLOCK_MIN_TX_FEE_PER_KB) {}
 
 BlockAssembler::BlockAssembler(const CChainParams &params,
                                const CTxMemPool &_mempool,
                                const Options &options)
     : chainparams(params), mempool(&_mempool) {
     blockMinFeeRate = options.blockMinFeeRate;
     // Limit size to between 1K and options.nExcessiveBlockSize -1K for sanity:
     nMaxGeneratedBlockSize = std::max<uint64_t>(
         1000, std::min<uint64_t>(options.nExcessiveBlockSize - 1000,
                                  options.nMaxGeneratedBlockSize));
+    // Calculate the max consensus sigchecks for this block.
+    auto nMaxBlockSigChecks =
+        GetMaxBlockSigChecksCount(options.nExcessiveBlockSize);
+    // Allow the full amount of signature check operations in lieu of a separate
+    // config option. (We are mining relayed transactions with validity cached
+    // by everyone else, and so the block will propagate quickly, regardless of
+    // how many sigchecks it contains.)
+    nMaxGeneratedBlockSigChecks = nMaxBlockSigChecks;
 }
 
 static BlockAssembler::Options DefaultOptions(const Config &config) {
     // Block resource limits
     // If -blockmaxsize is not given, limit to DEFAULT_MAX_GENERATED_BLOCK_SIZE
     // If only one is given, only restrict the specified resource.
     // If both are given, restrict both.
     BlockAssembler::Options options;
 
     options.nExcessiveBlockSize = config.GetMaxBlockSize();
 
     if (gArgs.IsArgSet("-blockmaxsize")) {
         options.nMaxGeneratedBlockSize =
             gArgs.GetArg("-blockmaxsize", DEFAULT_MAX_GENERATED_BLOCK_SIZE);
     }
 
     Amount n = Amount::zero();
     if (gArgs.IsArgSet("-blockmintxfee") &&
         ParseMoney(gArgs.GetArg("-blockmintxfee", ""), n)) {
         options.blockMinFeeRate = CFeeRate(n);
     }
 
     return options;
 }
 
 BlockAssembler::BlockAssembler(const Config &config, const CTxMemPool &_mempool)
     : BlockAssembler(config.GetChainParams(), _mempool,
                      DefaultOptions(config)) {}
 
 void BlockAssembler::resetBlock() {
     inBlock.clear();
 
     // Reserve space for coinbase tx.
     nBlockSize = 1000;
     nBlockSigOps = 100;
 
     // These counters do not include coinbase tx.
     nBlockTx = 0;
     nFees = Amount::zero();
 }
 
 std::unique_ptr<CBlockTemplate>
 BlockAssembler::CreateNewBlock(const CScript &scriptPubKeyIn) {
     int64_t nTimeStart = GetTimeMicros();
 
     resetBlock();
 
     pblocktemplate.reset(new CBlockTemplate());
     if (!pblocktemplate.get()) {
         return nullptr;
     }
 
     // Pointer for convenience.
     pblock = &pblocktemplate->block;
 
     // Add dummy coinbase tx as first transaction.  It is updated at the end.
     pblocktemplate->entries.emplace_back(CTransactionRef(), -SATOSHI, -1);
 
     LOCK2(cs_main, mempool->cs);
     CBlockIndex *pindexPrev = chainActive.Tip();
     assert(pindexPrev != nullptr);
     nHeight = pindexPrev->nHeight + 1;
 
     const Consensus::Params &consensusParams = chainparams.GetConsensus();
 
     pblock->nVersion = ComputeBlockVersion(pindexPrev, consensusParams);
     // -regtest only: allow overriding block.nVersion with
     // -blockversion=N to test forking scenarios
     if (chainparams.MineBlocksOnDemand()) {
         pblock->nVersion = gArgs.GetArg("-blockversion", pblock->nVersion);
     }
 
     pblock->nTime = GetAdjustedTime();
     nMedianTimePast = pindexPrev->GetMedianTimePast();
     nLockTimeCutoff =
         (STANDARD_LOCKTIME_VERIFY_FLAGS & LOCKTIME_MEDIAN_TIME_PAST)
             ? nMedianTimePast
             : pblock->GetBlockTime();
 
+    // After the sigchecks activation we repurpose the 'sigops' tracking in
+    // mempool/mining to actually track sigchecks instead. (Proper SigOps will
+    // not need to be counted any more since it's getting deactivated.)
+    fUseSigChecks = IsPhononEnabled(chainparams.GetConsensus(), pindexPrev);
+
     int nPackagesSelected = 0;
     int nDescendantsUpdated = 0;
     addPackageTxs(nPackagesSelected, nDescendantsUpdated);
 
     if (IsMagneticAnomalyEnabled(consensusParams, pindexPrev)) {
         // If magnetic anomaly is enabled, we make sure transaction are
         // canonically ordered.
         std::sort(std::begin(pblocktemplate->entries) + 1,
                   std::end(pblocktemplate->entries),
                   [](const CBlockTemplateEntry &a, const CBlockTemplateEntry &b)
                       -> bool { return a.tx->GetId() < b.tx->GetId(); });
     }
 
     // Copy all the transactions refs into the block
     pblock->vtx.reserve(pblocktemplate->entries.size());
     for (const CBlockTemplateEntry &entry : pblocktemplate->entries) {
         pblock->vtx.push_back(entry.tx);
     }
 
     int64_t nTime1 = GetTimeMicros();
 
     nLastBlockTx = nBlockTx;
     nLastBlockSize = nBlockSize;
 
     // Create coinbase transaction.
     CMutableTransaction coinbaseTx;
     coinbaseTx.vin.resize(1);
     coinbaseTx.vin[0].prevout = COutPoint();
     coinbaseTx.vout.resize(1);
     coinbaseTx.vout[0].scriptPubKey = scriptPubKeyIn;
     coinbaseTx.vout[0].nValue =
         nFees + GetBlockSubsidy(nHeight, consensusParams);
     coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
 
     // Make sure the coinbase is big enough.
     uint64_t coinbaseSize = ::GetSerializeSize(coinbaseTx, PROTOCOL_VERSION);
     if (coinbaseSize < MIN_TX_SIZE) {
         coinbaseTx.vin[0].scriptSig
             << std::vector<uint8_t>(MIN_TX_SIZE - coinbaseSize - 1);
     }
 
     pblocktemplate->entries[0].tx = MakeTransactionRef(coinbaseTx);
     pblocktemplate->entries[0].fees = -1 * nFees;
     pblock->vtx[0] = pblocktemplate->entries[0].tx;
 
     uint64_t nSerializeSize = GetSerializeSize(*pblock, PROTOCOL_VERSION);
 
     LogPrintf("CreateNewBlock(): total size: %u txs: %u fees: %ld sigops %d\n",
               nSerializeSize, nBlockTx, nFees, nBlockSigOps);
 
     // Fill in header.
     pblock->hashPrevBlock = pindexPrev->GetBlockHash();
     UpdateTime(pblock, consensusParams, pindexPrev);
     pblock->nBits = GetNextWorkRequired(pindexPrev, pblock, consensusParams);
     pblock->nNonce = 0;
     pblocktemplate->entries[0].sigOpCount = GetSigOpCountWithoutP2SH(
         *pblocktemplate->entries[0].tx, STANDARD_SCRIPT_VERIFY_FLAGS);
 
     CValidationState state;
     if (!TestBlockValidity(state, chainparams, *pblock, pindexPrev,
                            BlockValidationOptions(nMaxGeneratedBlockSize)
                                .withCheckPoW(false)
                                .withCheckMerkleRoot(false))) {
         throw std::runtime_error(strprintf("%s: TestBlockValidity failed: %s",
                                            __func__,
                                            FormatStateMessage(state)));
     }
     int64_t nTime2 = GetTimeMicros();
 
     LogPrint(BCLog::BENCH,
              "CreateNewBlock() packages: %.2fms (%d packages, %d updated "
              "descendants), validity: %.2fms (total %.2fms)\n",
              0.001 * (nTime1 - nTimeStart), nPackagesSelected,
              nDescendantsUpdated, 0.001 * (nTime2 - nTime1),
              0.001 * (nTime2 - nTimeStart));
 
     return std::move(pblocktemplate);
 }
 
 void BlockAssembler::onlyUnconfirmed(CTxMemPool::setEntries &testSet) {
     for (CTxMemPool::setEntries::iterator iit = testSet.begin();
          iit != testSet.end();) {
         // Only test txs not already in the block.
         if (inBlock.count(*iit)) {
             testSet.erase(iit++);
         } else {
             iit++;
         }
     }
 }
 
+uint64_t BlockAssembler::MaxBlockSigOpsCountForSize(uint64_t blockSize) const {
+    return fUseSigChecks ? nMaxGeneratedBlockSigChecks
+                         : GetMaxBlockSigOpsCount(blockSize);
+}
+
 bool BlockAssembler::TestPackage(uint64_t packageSize,
                                  int64_t packageSigOps) const {
     auto blockSizeWithPackage = nBlockSize + packageSize;
     if (blockSizeWithPackage >= nMaxGeneratedBlockSize) {
         return false;
     }
 
     if (nBlockSigOps + packageSigOps >=
-        GetMaxBlockSigOpsCount(blockSizeWithPackage)) {
+        MaxBlockSigOpsCountForSize(blockSizeWithPackage)) {
         return false;
     }
 
     return true;
 }
 
 /**
  * Perform transaction-level checks before adding to block:
  * - Transaction finality (locktime)
  * - Serialized size (in case -blockmaxsize is in use)
  */
 bool BlockAssembler::TestPackageTransactions(
     const CTxMemPool::setEntries &package) {
     uint64_t nPotentialBlockSize = nBlockSize;
     for (CTxMemPool::txiter it : package) {
         CValidationState state;
         if (!ContextualCheckTransaction(chainparams.GetConsensus(), it->GetTx(),
                                         state, nHeight, nLockTimeCutoff,
                                         nMedianTimePast)) {
             return false;
         }
 
         uint64_t nTxSize = ::GetSerializeSize(it->GetTx(), PROTOCOL_VERSION);
         if (nPotentialBlockSize + nTxSize >= nMaxGeneratedBlockSize) {
             return false;
         }
 
         nPotentialBlockSize += nTxSize;
     }
 
     return true;
 }
 
 void BlockAssembler::AddToBlock(CTxMemPool::txiter iter) {
     pblocktemplate->entries.emplace_back(iter->GetSharedTx(), iter->GetFee(),
                                          iter->GetSigOpCount());
     nBlockSize += iter->GetTxSize();
     ++nBlockTx;
     nBlockSigOps += iter->GetSigOpCount();
     nFees += iter->GetFee();
     inBlock.insert(iter);
 
     bool fPrintPriority =
         gArgs.GetBoolArg("-printpriority", DEFAULT_PRINTPRIORITY);
     if (fPrintPriority) {
         LogPrintf(
             "fee %s txid %s\n",
             CFeeRate(iter->GetModifiedFee(), iter->GetTxSize()).ToString(),
             iter->GetTx().GetId().ToString());
     }
 }
 
 int BlockAssembler::UpdatePackagesForAdded(
     const CTxMemPool::setEntries &alreadyAdded,
     indexed_modified_transaction_set &mapModifiedTx) {
     int nDescendantsUpdated = 0;
     for (CTxMemPool::txiter it : alreadyAdded) {
         CTxMemPool::setEntries descendants;
         mempool->CalculateDescendants(it, descendants);
         // Insert all descendants (not yet in block) into the modified set.
         for (CTxMemPool::txiter desc : descendants) {
             if (alreadyAdded.count(desc)) {
                 continue;
             }
 
             ++nDescendantsUpdated;
             modtxiter mit = mapModifiedTx.find(desc);
             if (mit == mapModifiedTx.end()) {
                 CTxMemPoolModifiedEntry modEntry(desc);
                 modEntry.nSizeWithAncestors -= it->GetTxSize();
                 modEntry.nModFeesWithAncestors -= it->GetModifiedFee();
                 modEntry.nSigOpCountWithAncestors -= it->GetSigOpCount();
                 mapModifiedTx.insert(modEntry);
             } else {
                 mapModifiedTx.modify(mit, update_for_parent_inclusion(it));
             }
         }
     }
 
     return nDescendantsUpdated;
 }
 
 // Skip entries in mapTx that are already in a block or are present in
 // mapModifiedTx (which implies that the mapTx ancestor state is stale due to
 // ancestor inclusion in the block). Also skip transactions that we've already
 // failed to add. This can happen if we consider a transaction in mapModifiedTx
 // and it fails: we can then potentially consider it again while walking mapTx.
 // It's currently guaranteed to fail again, but as a belt-and-suspenders check
 // we put it in failedTx and avoid re-evaluation, since the re-evaluation would
 // be using cached size/sigops/fee values that are not actually correct.
 bool BlockAssembler::SkipMapTxEntry(
     CTxMemPool::txiter it, indexed_modified_transaction_set &mapModifiedTx,
     CTxMemPool::setEntries &failedTx) {
     assert(it != mempool->mapTx.end());
     return mapModifiedTx.count(it) || inBlock.count(it) || failedTx.count(it);
 }
 
 void BlockAssembler::SortForBlock(
     const CTxMemPool::setEntries &package,
     std::vector<CTxMemPool::txiter> &sortedEntries) {
     // Sort package by ancestor count. If a transaction A depends on transaction
     // B, then A's ancestor count must be greater than B's. So this is
     // sufficient to validly order the transactions for block inclusion.
     sortedEntries.clear();
     sortedEntries.insert(sortedEntries.begin(), package.begin(), package.end());
     std::sort(sortedEntries.begin(), sortedEntries.end(),
               CompareTxIterByAncestorCount());
 }
 
 /**
  * addPackageTx includes transactions paying a fee by ensuring that
  * the partial ordering of transactions is maintained.  That is to say
  * children come after parents, despite having a potentially larger fee.
  * @param[out] nPackagesSelected    How many packages were selected
  * @param[out] nDescendantsUpdated  Number of descendant transactions updated
  */
 void BlockAssembler::addPackageTxs(int &nPackagesSelected,
                                    int &nDescendantsUpdated) {
     // selection algorithm orders the mempool based on feerate of a
     // transaction including all unconfirmed ancestors. Since we don't remove
     // transactions from the mempool as we select them for block inclusion, we
     // need an alternate method of updating the feerate of a transaction with
     // its not-yet-selected ancestors as we go. This is accomplished by
     // walking the in-mempool descendants of selected transactions and storing
     // a temporary modified state in mapModifiedTxs. Each time through the
     // loop, we compare the best transaction in mapModifiedTxs with the next
     // transaction in the mempool to decide what transaction package to work
     // on next.
 
     // mapModifiedTx will store sorted packages after they are modified because
     // some of their txs are already in the block.
     indexed_modified_transaction_set mapModifiedTx;
     // Keep track of entries that failed inclusion, to avoid duplicate work.
     CTxMemPool::setEntries failedTx;
 
     // Start by adding all descendants of previously added txs to mapModifiedTx
     // and modifying them for their already included ancestors.
     UpdatePackagesForAdded(inBlock, mapModifiedTx);
 
     CTxMemPool::indexed_transaction_set::index<ancestor_score>::type::iterator
         mi = mempool->mapTx.get<ancestor_score>().begin();
     CTxMemPool::txiter iter;
 
     // Limit the number of attempts to add transactions to the block when it is
     // close to full; this is just a simple heuristic to finish quickly if the
     // mempool has a lot of entries.
     const int64_t MAX_CONSECUTIVE_FAILURES = 1000;
     int64_t nConsecutiveFailed = 0;
 
     while (mi != mempool->mapTx.get<ancestor_score>().end() ||
            !mapModifiedTx.empty()) {
         // First try to find a new transaction in mapTx to evaluate.
         if (mi != mempool->mapTx.get<ancestor_score>().end() &&
             SkipMapTxEntry(mempool->mapTx.project<0>(mi), mapModifiedTx,
                            failedTx)) {
             ++mi;
             continue;
         }
 
         // Now that mi is not stale, determine which transaction to evaluate:
         // the next entry from mapTx, or the best from mapModifiedTx?
         bool fUsingModified = false;
 
         modtxscoreiter modit = mapModifiedTx.get<ancestor_score>().begin();
         if (mi == mempool->mapTx.get<ancestor_score>().end()) {
             // We're out of entries in mapTx; use the entry from mapModifiedTx
             iter = modit->iter;
             fUsingModified = true;
         } else {
             // Try to compare the mapTx entry to the mapModifiedTx entry.
             iter = mempool->mapTx.project<0>(mi);
             if (modit != mapModifiedTx.get<ancestor_score>().end() &&
                 CompareTxMemPoolEntryByAncestorFee()(
                     *modit, CTxMemPoolModifiedEntry(iter))) {
                 // The best entry in mapModifiedTx has higher score than the one
                 // from mapTx. Switch which transaction (package) to consider
                 iter = modit->iter;
                 fUsingModified = true;
             } else {
                 // Either no entry in mapModifiedTx, or it's worse than mapTx.
                 // Increment mi for the next loop iteration.
                 ++mi;
             }
         }
 
         // We skip mapTx entries that are inBlock, and mapModifiedTx shouldn't
         // contain anything that is inBlock.
         assert(!inBlock.count(iter));
 
         uint64_t packageSize = iter->GetSizeWithAncestors();
         Amount packageFees = iter->GetModFeesWithAncestors();
         int64_t packageSigOps = iter->GetSigOpCountWithAncestors();
         if (fUsingModified) {
             packageSize = modit->nSizeWithAncestors;
             packageFees = modit->nModFeesWithAncestors;
             packageSigOps = modit->nSigOpCountWithAncestors;
         }
 
         if (packageFees < blockMinFeeRate.GetFee(packageSize)) {
             // Don't include this package, but don't stop yet because something
             // else we might consider may have a sufficient fee rate (since txes
             // are ordered by virtualsize feerate, not actual feerate).
             if (fUsingModified) {
                 // Since we always look at the best entry in mapModifiedTx, we
                 // must erase failed entries so that we can consider the next
                 // best entry on the next loop iteration
                 mapModifiedTx.get<ancestor_score>().erase(modit);
                 failedTx.insert(iter);
             }
             continue;
         }
 
         // The following must not use virtual size since TestPackage relies on
         // having an accurate call to
         // GetMaxBlockSigOpsCount(blockSizeWithPackage).
         if (!TestPackage(packageSize, packageSigOps)) {
             if (fUsingModified) {
                 // Since we always look at the best entry in mapModifiedTx, we
                 // must erase failed entries so that we can consider the next
                 // best entry on the next loop iteration
                 mapModifiedTx.get<ancestor_score>().erase(modit);
                 failedTx.insert(iter);
             }
 
             ++nConsecutiveFailed;
 
             if (nConsecutiveFailed > MAX_CONSECUTIVE_FAILURES &&
                 nBlockSize > nMaxGeneratedBlockSize - 1000) {
                 // Give up if we're close to full and haven't succeeded in a
                 // while.
                 break;
             }
 
             continue;
         }
 
         CTxMemPool::setEntries ancestors;
         uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
         std::string dummy;
         mempool->CalculateMemPoolAncestors(*iter, ancestors, nNoLimit, nNoLimit,
                                            nNoLimit, nNoLimit, dummy, false);
 
         onlyUnconfirmed(ancestors);
         ancestors.insert(iter);
 
         // Test if all tx's are Final.
         if (!TestPackageTransactions(ancestors)) {
             if (fUsingModified) {
                 mapModifiedTx.get<ancestor_score>().erase(modit);
                 failedTx.insert(iter);
             }
             continue;
         }
 
         // This transaction will make it in; reset the failed counter.
         nConsecutiveFailed = 0;
 
         // Package can be added. Sort the entries in a valid order.
         std::vector<CTxMemPool::txiter> sortedEntries;
         SortForBlock(ancestors, sortedEntries);
 
         for (auto &entry : sortedEntries) {
             AddToBlock(entry);
             // Erase from the modified set, if present
             mapModifiedTx.erase(entry);
         }
 
         ++nPackagesSelected;
 
         // Update transactions that depend on each of these
         nDescendantsUpdated += UpdatePackagesForAdded(ancestors, mapModifiedTx);
     }
 }
 
 static const std::vector<uint8_t>
 getExcessiveBlockSizeSig(uint64_t nExcessiveBlockSize) {
     std::string cbmsg = "/EB" + getSubVersionEB(nExcessiveBlockSize) + "/";
     std::vector<uint8_t> vec(cbmsg.begin(), cbmsg.end());
     return vec;
 }
 
 void IncrementExtraNonce(CBlock *pblock, const CBlockIndex *pindexPrev,
                          uint64_t nExcessiveBlockSize,
                          unsigned int &nExtraNonce) {
     // Update nExtraNonce
     static uint256 hashPrevBlock;
     if (hashPrevBlock != pblock->hashPrevBlock) {
         nExtraNonce = 0;
         hashPrevBlock = pblock->hashPrevBlock;
     }
 
     ++nExtraNonce;
     // Height first in coinbase required for block.version=2
     unsigned int nHeight = pindexPrev->nHeight + 1;
     CMutableTransaction txCoinbase(*pblock->vtx[0]);
     txCoinbase.vin[0].scriptSig =
         (CScript() << nHeight << CScriptNum(nExtraNonce)
                    << getExcessiveBlockSizeSig(nExcessiveBlockSize)) +
         COINBASE_FLAGS;
 
     // Make sure the coinbase is big enough.
     uint64_t coinbaseSize = ::GetSerializeSize(txCoinbase, PROTOCOL_VERSION);
     if (coinbaseSize < MIN_TX_SIZE) {
         txCoinbase.vin[0].scriptSig
             << std::vector<uint8_t>(MIN_TX_SIZE - coinbaseSize - 1);
     }
 
     assert(txCoinbase.vin[0].scriptSig.size() <= MAX_COINBASE_SCRIPTSIG_SIZE);
     assert(::GetSerializeSize(txCoinbase, PROTOCOL_VERSION) >= MIN_TX_SIZE);
 
     pblock->vtx[0] = MakeTransactionRef(std::move(txCoinbase));
     pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);
 }
diff --git a/src/miner.h b/src/miner.h
index e93b6d17f3..3c4a9e3d7d 100644
--- a/src/miner.h
+++ b/src/miner.h
@@ -1,231 +1,240 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #ifndef BITCOIN_MINER_H
 #define BITCOIN_MINER_H
 
 #include <primitives/block.h>
 #include <txmempool.h>
 
 #include <boost/multi_index/ordered_index.hpp>
 #include <boost/multi_index_container.hpp>
 
 #include <cstdint>
 #include <memory>
 
 class CBlockIndex;
 class CChainParams;
 class Config;
 class CScript;
 
 namespace Consensus {
 struct Params;
 }
 
 static const bool DEFAULT_PRINTPRIORITY = false;
 
 struct CBlockTemplateEntry {
     CTransactionRef tx;
     Amount fees;
     int64_t sigOpCount;
 
     CBlockTemplateEntry(CTransactionRef _tx, Amount _fees, int64_t _sigOpCount)
         : tx(_tx), fees(_fees), sigOpCount(_sigOpCount){};
 };
 
 struct CBlockTemplate {
     CBlock block;
 
     std::vector<CBlockTemplateEntry> entries;
 };
 
 // Container for tracking updates to ancestor feerate as we include (parent)
 // transactions in a block
 struct CTxMemPoolModifiedEntry {
     explicit CTxMemPoolModifiedEntry(CTxMemPool::txiter entry) {
         iter = entry;
         nSizeWithAncestors = entry->GetSizeWithAncestors();
         nModFeesWithAncestors = entry->GetModFeesWithAncestors();
         nSigOpCountWithAncestors = entry->GetSigOpCountWithAncestors();
     }
 
     Amount GetModifiedFee() const { return iter->GetModifiedFee(); }
     uint64_t GetSizeWithAncestors() const { return nSizeWithAncestors; }
     uint64_t GetVirtualSizeWithAncestors() const;
     Amount GetModFeesWithAncestors() const { return nModFeesWithAncestors; }
     size_t GetTxSize() const { return iter->GetTxSize(); }
     size_t GetTxVirtualSize() const { return iter->GetTxVirtualSize(); }
     const CTransaction &GetTx() const { return iter->GetTx(); }
 
     CTxMemPool::txiter iter;
     uint64_t nSizeWithAncestors;
     Amount nModFeesWithAncestors;
     int64_t nSigOpCountWithAncestors;
 };
 
 /**
  * Comparator for CTxMemPool::txiter objects.
  * It simply compares the internal memory address of the CTxMemPoolEntry object
  * pointed to. This means it has no meaning, and is only useful for using them
  * as key in other indexes.
  */
 struct CompareCTxMemPoolIter {
     bool operator()(const CTxMemPool::txiter &a,
                     const CTxMemPool::txiter &b) const {
         return &(*a) < &(*b);
     }
 };
 
 struct modifiedentry_iter {
     typedef CTxMemPool::txiter result_type;
     result_type operator()(const CTxMemPoolModifiedEntry &entry) const {
         return entry.iter;
     }
 };
 
 // A comparator that sorts transactions based on number of ancestors.
 // This is sufficient to sort an ancestor package in an order that is valid
 // to appear in a block.
 struct CompareTxIterByAncestorCount {
     bool operator()(const CTxMemPool::txiter &a,
                     const CTxMemPool::txiter &b) const {
         if (a->GetCountWithAncestors() != b->GetCountWithAncestors()) {
             return a->GetCountWithAncestors() < b->GetCountWithAncestors();
         }
         return CTxMemPool::CompareIteratorById()(a, b);
     }
 };
 
 typedef boost::multi_index_container<
     CTxMemPoolModifiedEntry,
     boost::multi_index::indexed_by<
         boost::multi_index::ordered_unique<modifiedentry_iter,
                                            CompareCTxMemPoolIter>,
         // sorted by modified ancestor fee rate
         boost::multi_index::ordered_non_unique<
             // Reuse same tag from CTxMemPool's similar index
             boost::multi_index::tag<ancestor_score>,
             boost::multi_index::identity<CTxMemPoolModifiedEntry>,
             CompareTxMemPoolEntryByAncestorFee>>>
     indexed_modified_transaction_set;
 
 typedef indexed_modified_transaction_set::nth_index<0>::type::iterator
     modtxiter;
 typedef indexed_modified_transaction_set::index<ancestor_score>::type::iterator
     modtxscoreiter;
 
 struct update_for_parent_inclusion {
     explicit update_for_parent_inclusion(CTxMemPool::txiter it) : iter(it) {}
 
     void operator()(CTxMemPoolModifiedEntry &e) {
         e.nModFeesWithAncestors -= iter->GetFee();
         e.nSizeWithAncestors -= iter->GetTxSize();
         e.nSigOpCountWithAncestors -= iter->GetSigOpCount();
     }
 
     CTxMemPool::txiter iter;
 };
 
 /** Generate a new block, without valid proof-of-work */
 class BlockAssembler {
 private:
     // The constructed block template
     std::unique_ptr<CBlockTemplate> pblocktemplate;
     // A convenience pointer that always refers to the CBlock in pblocktemplate
     CBlock *pblock;
 
     // Configuration parameters for the block size
     uint64_t nMaxGeneratedBlockSize;
+    uint64_t nMaxGeneratedBlockSigChecks;
     CFeeRate blockMinFeeRate;
 
     // Information on the current status of the block
     uint64_t nBlockSize;
     uint64_t nBlockTx;
     uint64_t nBlockSigOps;
     Amount nFees;
     CTxMemPool::setEntries inBlock;
 
     // Chain context for the block
     int nHeight;
     int64_t nLockTimeCutoff;
     int64_t nMedianTimePast;
     const CChainParams &chainparams;
+    bool fUseSigChecks;
 
     const CTxMemPool *mempool;
 
 public:
     struct Options {
         Options();
         uint64_t nExcessiveBlockSize;
         uint64_t nMaxGeneratedBlockSize;
         CFeeRate blockMinFeeRate;
     };
 
     BlockAssembler(const Config &config, const CTxMemPool &_mempool);
     BlockAssembler(const CChainParams &params, const CTxMemPool &_mempool,
                    const Options &options);
 
     /** Construct a new block template with coinbase to scriptPubKeyIn */
     std::unique_ptr<CBlockTemplate>
     CreateNewBlock(const CScript &scriptPubKeyIn);
 
     uint64_t GetMaxGeneratedBlockSize() const { return nMaxGeneratedBlockSize; }
 
 private:
     // utility functions
     /** Clear the block's state and prepare for assembling a new block */
     void resetBlock();
     /** Add a tx to the block */
     void AddToBlock(CTxMemPool::txiter iter);
 
+    /**
+     * Calculate the "SigOps" limit for a given block size (may actually be the
+     * SigChecks limit which is independent of blockSize, depending on
+     * fUseSigChecks)
+     */
+    uint64_t MaxBlockSigOpsCountForSize(uint64_t blockSize) const;
+
     // Methods for how to add transactions to a block.
     /**
      * Add transactions based on feerate including unconfirmed ancestors.
      * Increments nPackagesSelected / nDescendantsUpdated with corresponding
      * statistics from the package selection (for logging statistics).
      */
     void addPackageTxs(int &nPackagesSelected, int &nDescendantsUpdated)
         EXCLUSIVE_LOCKS_REQUIRED(mempool->cs);
 
     // helper functions for addPackageTxs()
     /** Remove confirmed (inBlock) entries from given set */
     void onlyUnconfirmed(CTxMemPool::setEntries &testSet);
     /** Test if a new package would "fit" in the block */
     bool TestPackage(uint64_t packageSize, int64_t packageSigOpCount) const;
     /**
      * Perform checks on each transaction in a package:
      * locktime, serialized size (if necessary). These checks should always
      * succeed, and they're here only as an extra check in case of suboptimal
      * node configuration.
      */
     bool TestPackageTransactions(const CTxMemPool::setEntries &package);
     /**
      * Return true if given transaction from mapTx has already been evaluated,
      * or if the transaction's cached data in mapTx is incorrect.
      */
     bool SkipMapTxEntry(CTxMemPool::txiter it,
                         indexed_modified_transaction_set &mapModifiedTx,
                         CTxMemPool::setEntries &failedTx)
         EXCLUSIVE_LOCKS_REQUIRED(mempool->cs);
     /** Sort the package in an order that is valid to appear in a block */
     void SortForBlock(const CTxMemPool::setEntries &package,
                       std::vector<CTxMemPool::txiter> &sortedEntries);
     /**
      * Add descendants of given transactions to mapModifiedTx with ancestor
      * state updated assuming given transactions are inBlock. Returns number of
      * updated descendants.
      */
     int UpdatePackagesForAdded(const CTxMemPool::setEntries &alreadyAdded,
                                indexed_modified_transaction_set &mapModifiedTx)
         EXCLUSIVE_LOCKS_REQUIRED(mempool->cs);
 };
 
 /** Modify the extranonce in a block */
 void IncrementExtraNonce(CBlock *pblock, const CBlockIndex *pindexPrev,
                          uint64_t nExcessiveBlockSize,
                          unsigned int &nExtraNonce);
 int64_t UpdateTime(CBlockHeader *pblock, const Consensus::Params &params,
                    const CBlockIndex *pindexPrev);
 #endif // BITCOIN_MINER_H
diff --git a/src/txmempool.h b/src/txmempool.h
index c6d314f541..640599896d 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -1,983 +1,988 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #ifndef BITCOIN_TXMEMPOOL_H
 #define BITCOIN_TXMEMPOOL_H
 
 #include <amount.h>
 #include <coins.h>
 #include <crypto/siphash.h>
 #include <indirectmap.h>
 #include <primitives/transaction.h>
 #include <random.h>
 #include <sync.h>
 
 #include <boost/multi_index/hashed_index.hpp>
 #include <boost/multi_index/ordered_index.hpp>
 #include <boost/multi_index/sequenced_index.hpp>
 #include <boost/multi_index_container.hpp>
 #include <boost/signals2/signal.hpp>
 
 #include <map>
 #include <set>
 #include <string>
 #include <utility>
 #include <vector>
 
 class CBlockIndex;
 class Config;
 
 extern CCriticalSection cs_main;
 
 /**
  * Fake height value used in Coins to signify they are only in the memory
  * pool(since 0.8)
  */
 static const uint32_t MEMPOOL_HEIGHT = 0x7FFFFFFF;
 
 struct LockPoints {
     // Will be set to the blockchain height and median time past values that
     // would be necessary to satisfy all relative locktime constraints (BIP68)
     // of this tx given our view of block chain history
     int height;
     int64_t time;
     // As long as the current chain descends from the highest height block
     // containing one of the inputs used in the calculation, then the cached
     // values are still valid even after a reorg.
     CBlockIndex *maxInputBlock;
 
     LockPoints() : height(0), time(0), maxInputBlock(nullptr) {}
 };
 
 class CTxMemPool;
 
 /** \class CTxMemPoolEntry
  *
  * CTxMemPoolEntry stores data about the corresponding transaction, as well as
  * data about all in-mempool transactions that depend on the transaction
  * ("descendant" transactions).
  *
  * When a new entry is added to the mempool, we update the descendant state
  * (nCountWithDescendants, nSizeWithDescendants, and nModFeesWithDescendants)
  * for all ancestors of the newly added transaction.
  */
 
 class CTxMemPoolEntry {
 private:
     const CTransactionRef tx;
     //! Cached to avoid expensive parent-transaction lookups
     const Amount nFee;
     //! ... and avoid recomputing tx size
     const size_t nTxSize;
     //! ... and total memory usage
     const size_t nUsageSize;
     //! Local time when entering the mempool
     const int64_t nTime;
     //! Chain height when entering the mempool
     const unsigned int entryHeight;
     //! keep track of transactions that spend a coinbase
     const bool spendsCoinbase;
-    //! Total sigop plus P2SH sigops count
+    /**
+     * Total sigop plus P2SH sigops count.
+     * After the sigchecks activation we repurpose the 'sigops' tracking in
+     * mempool/mining to actually track sigchecks instead. (Proper SigOps will
+     * not need to be counted any more since it's getting deactivated.)
+     */
     const int64_t sigOpCount;
     //! Used for determining the priority of the transaction for mining in a
     //! block
     Amount feeDelta;
     //! Track the height and time at which tx was final
     LockPoints lockPoints;
 
     // Information about descendants of this transaction that are in the
     // mempool; if we remove this transaction we must remove all of these
     // descendants as well.
     //! number of descendant transactions
     uint64_t nCountWithDescendants;
     //! ... and size
     uint64_t nSizeWithDescendants;
     //! ... and total fees (all including us)
     Amount nModFeesWithDescendants;
     //! ... and sigop count
     int64_t nSigOpCountWithDescendants;
 
     // Analogous statistics for ancestor transactions
     uint64_t nCountWithAncestors;
     uint64_t nSizeWithAncestors;
     Amount nModFeesWithAncestors;
     int64_t nSigOpCountWithAncestors;
 
 public:
     CTxMemPoolEntry(const CTransactionRef &_tx, const Amount _nFee,
                     int64_t _nTime, unsigned int _entryHeight,
                     bool spendsCoinbase, int64_t _nSigOpCount, LockPoints lp);
 
     const CTransaction &GetTx() const { return *this->tx; }
     CTransactionRef GetSharedTx() const { return this->tx; }
     const Amount GetFee() const { return nFee; }
     size_t GetTxSize() const { return nTxSize; }
     size_t GetTxVirtualSize() const;
 
     int64_t GetTime() const { return nTime; }
     unsigned int GetHeight() const { return entryHeight; }
     int64_t GetSigOpCount() const { return sigOpCount; }
     Amount GetModifiedFee() const { return nFee + feeDelta; }
     size_t DynamicMemoryUsage() const { return nUsageSize; }
     const LockPoints &GetLockPoints() const { return lockPoints; }
 
     // Adjusts the descendant state.
     void UpdateDescendantState(int64_t modifySize, Amount modifyFee,
                                int64_t modifyCount, int64_t modifySigOpCount);
     // Adjusts the ancestor state
     void UpdateAncestorState(int64_t modifySize, Amount modifyFee,
                              int64_t modifyCount, int modifySigOps);
     // Updates the fee delta used for mining priority score, and the
     // modified fees with descendants.
     void UpdateFeeDelta(Amount feeDelta);
     // Update the LockPoints after a reorg
     void UpdateLockPoints(const LockPoints &lp);
 
     uint64_t GetCountWithDescendants() const { return nCountWithDescendants; }
     uint64_t GetSizeWithDescendants() const { return nSizeWithDescendants; }
     uint64_t GetVirtualSizeWithDescendants() const;
     Amount GetModFeesWithDescendants() const { return nModFeesWithDescendants; }
     int64_t GetSigOpCountWithDescendants() const {
         return nSigOpCountWithDescendants;
     }
 
     bool GetSpendsCoinbase() const { return spendsCoinbase; }
 
     uint64_t GetCountWithAncestors() const { return nCountWithAncestors; }
     uint64_t GetSizeWithAncestors() const { return nSizeWithAncestors; }
     uint64_t GetVirtualSizeWithAncestors() const;
     Amount GetModFeesWithAncestors() const { return nModFeesWithAncestors; }
     int64_t GetSigOpCountWithAncestors() const {
         return nSigOpCountWithAncestors;
     }
 
     //! Index in mempool's vTxHashes
     mutable size_t vTxHashesIdx;
 };
 
 // Helpers for modifying CTxMemPool::mapTx, which is a boost multi_index.
 struct update_descendant_state {
     update_descendant_state(int64_t _modifySize, Amount _modifyFee,
                             int64_t _modifyCount, int64_t _modifySigOpCount)
         : modifySize(_modifySize), modifyFee(_modifyFee),
           modifyCount(_modifyCount), modifySigOpCount(_modifySigOpCount) {}
 
     void operator()(CTxMemPoolEntry &e) {
         e.UpdateDescendantState(modifySize, modifyFee, modifyCount,
                                 modifySigOpCount);
     }
 
 private:
     int64_t modifySize;
     Amount modifyFee;
     int64_t modifyCount;
     int64_t modifySigOpCount;
 };
 
 struct update_ancestor_state {
     update_ancestor_state(int64_t _modifySize, Amount _modifyFee,
                           int64_t _modifyCount, int64_t _modifySigOpCount)
         : modifySize(_modifySize), modifyFee(_modifyFee),
           modifyCount(_modifyCount), modifySigOpCount(_modifySigOpCount) {}
 
     void operator()(CTxMemPoolEntry &e) {
         e.UpdateAncestorState(modifySize, modifyFee, modifyCount,
                               modifySigOpCount);
     }
 
 private:
     int64_t modifySize;
     Amount modifyFee;
     int64_t modifyCount;
     int64_t modifySigOpCount;
 };
 
 struct update_fee_delta {
     explicit update_fee_delta(Amount _feeDelta) : feeDelta(_feeDelta) {}
 
     void operator()(CTxMemPoolEntry &e) { e.UpdateFeeDelta(feeDelta); }
 
 private:
     Amount feeDelta;
 };
 
 struct update_lock_points {
     explicit update_lock_points(const LockPoints &_lp) : lp(_lp) {}
 
     void operator()(CTxMemPoolEntry &e) { e.UpdateLockPoints(lp); }
 
 private:
     const LockPoints &lp;
 };
 
 // extracts a transaction id from CTxMemPoolEntry or CTransactionRef
 struct mempoolentry_txid {
     typedef TxId result_type;
     result_type operator()(const CTxMemPoolEntry &entry) const {
         return entry.GetTx().GetId();
     }
 
     result_type operator()(const CTransactionRef &tx) const {
         return tx->GetId();
     }
 };
 
 /** \class CompareTxMemPoolEntryByDescendantScore
  *
  *  Sort an entry by max(score/size of entry's tx, score/size with all
  * descendants).
  */
 class CompareTxMemPoolEntryByDescendantScore {
 public:
     bool operator()(const CTxMemPoolEntry &a, const CTxMemPoolEntry &b) const {
         double a_mod_fee, a_size, b_mod_fee, b_size;
 
         GetModFeeAndSize(a, a_mod_fee, a_size);
         GetModFeeAndSize(b, b_mod_fee, b_size);
 
         // Avoid division by rewriting (a/b > c/d) as (a*d > c*b).
         double f1 = a_mod_fee * b_size;
         double f2 = a_size * b_mod_fee;
 
         if (f1 == f2) {
             return a.GetTime() >= b.GetTime();
         }
         return f1 < f2;
     }
 
     // Return the fee/size we're using for sorting this entry.
     void GetModFeeAndSize(const CTxMemPoolEntry &a, double &mod_fee,
                           double &size) const {
         // Compare feerate with descendants to feerate of the transaction, and
         // return the fee/size for the max.
         double f1 =
             a.GetVirtualSizeWithDescendants() * (a.GetModifiedFee() / SATOSHI);
         double f2 =
             a.GetTxVirtualSize() * (a.GetModFeesWithDescendants() / SATOSHI);
 
         if (f2 > f1) {
             mod_fee = a.GetModFeesWithDescendants() / SATOSHI;
             size = a.GetVirtualSizeWithDescendants();
         } else {
             mod_fee = a.GetModifiedFee() / SATOSHI;
             size = a.GetTxVirtualSize();
         }
     }
 };
 
 /** \class CompareTxMemPoolEntryByScore
  *
  *  Sort by feerate of entry (fee/size) in descending order
  *  This is only used for transaction relay, so we use GetFee()
  *  instead of GetModifiedFee() to avoid leaking prioritization
  *  information via the sort order.
  */
 class CompareTxMemPoolEntryByScore {
 public:
     bool operator()(const CTxMemPoolEntry &a, const CTxMemPoolEntry &b) const {
         double f1 = b.GetTxSize() * (a.GetFee() / SATOSHI);
         double f2 = a.GetTxSize() * (b.GetFee() / SATOSHI);
         if (f1 == f2) {
             return b.GetTx().GetId() < a.GetTx().GetId();
         }
         return f1 > f2;
     }
 };
 
 class CompareTxMemPoolEntryByEntryTime {
 public:
     bool operator()(const CTxMemPoolEntry &a, const CTxMemPoolEntry &b) const {
         return a.GetTime() < b.GetTime();
     }
 };
 
 /** \class CompareTxMemPoolEntryByAncestorScore
  *
  *  Sort an entry by min(score/size of entry's tx, score/size with all
  * ancestors).
  */
 class CompareTxMemPoolEntryByAncestorFee {
 public:
     template <typename T> bool operator()(const T &a, const T &b) const {
         double a_mod_fee, a_size, b_mod_fee, b_size;
 
         GetModFeeAndSize(a, a_mod_fee, a_size);
         GetModFeeAndSize(b, b_mod_fee, b_size);
 
         // Avoid division by rewriting (a/b > c/d) as (a*d > c*b).
         double f1 = a_mod_fee * b_size;
         double f2 = a_size * b_mod_fee;
 
         if (f1 == f2) {
             return a.GetTx().GetId() < b.GetTx().GetId();
         }
         return f1 > f2;
     }
 
     // Return the fee/size we're using for sorting this entry.
     template <typename T>
     void GetModFeeAndSize(const T &a, double &mod_fee, double &size) const {
         // Compare feerate with ancestors to feerate of the transaction, and
         // return the fee/size for the min.
         double f1 =
             a.GetVirtualSizeWithAncestors() * (a.GetModifiedFee() / SATOSHI);
         double f2 =
             a.GetTxVirtualSize() * (a.GetModFeesWithAncestors() / SATOSHI);
 
         if (f1 > f2) {
             mod_fee = a.GetModFeesWithAncestors() / SATOSHI;
             size = a.GetVirtualSizeWithAncestors();
         } else {
             mod_fee = a.GetModifiedFee() / SATOSHI;
             size = a.GetTxVirtualSize();
         }
     }
 };
 
 // Multi_index tag names
 struct descendant_score {};
 struct entry_time {};
 struct ancestor_score {};
 
 /**
  * Information about a mempool transaction.
  */
 struct TxMempoolInfo {
     /** The transaction itself */
     CTransactionRef tx;
 
     /** Time the transaction entered the mempool. */
     int64_t nTime;
 
     /** Feerate of the transaction. */
     CFeeRate feeRate;
 
     /** The fee delta. */
     Amount nFeeDelta;
 };
 
 /**
  * Reason why a transaction was removed from the mempool, this is passed to the
  * notification signal.
  */
 enum class MemPoolRemovalReason {
     //! Manually removed or unknown reason
     UNKNOWN = 0,
     //! Expired from mempool
     EXPIRY,
     //! Removed in size limiting
     SIZELIMIT,
     //! Removed for reorganization
     REORG,
     //! Removed for block
     BLOCK,
     //! Removed for conflict with in-block transaction
     CONFLICT,
     //! Removed for replacement
     REPLACED
 };
 
 class SaltedTxidHasher {
 private:
     /** Salt */
     const uint64_t k0, k1;
 
 public:
     SaltedTxidHasher();
 
     size_t operator()(const TxId &txid) const {
         return SipHashUint256(k0, k1, txid);
     }
 };
 
 /**
  * CTxMemPool stores valid-according-to-the-current-best-chain transactions that
  * may be included in the next block.
  *
  * Transactions are added when they are seen on the network (or created by the
  * local node), but not all transactions seen are added to the pool. For
  * example, the following new transactions will not be added to the mempool:
  * - a transaction which doesn't meet the minimum fee requirements.
  * - a new transaction that double-spends an input of a transaction already in
  * the pool where the new transaction does not meet the Replace-By-Fee
  * requirements as defined in BIP 125.
  * - a non-standard transaction.
  *
  * CTxMemPool::mapTx, and CTxMemPoolEntry bookkeeping:
  *
  * mapTx is a boost::multi_index that sorts the mempool on 4 criteria:
  * - transaction hash
  * - descendant feerate [we use max(feerate of tx, feerate of tx with all
  * descendants)]
  * - time in mempool
  * - ancestor feerate [we use min(feerate of tx, feerate of tx with all
  * unconfirmed ancestors)]
  *
  * Note: the term "descendant" refers to in-mempool transactions that depend on
  * this one, while "ancestor" refers to in-mempool transactions that a given
  * transaction depends on.
  *
  * In order for the feerate sort to remain correct, we must update transactions
  * in the mempool when new descendants arrive. To facilitate this, we track the
  * set of in-mempool direct parents and direct children in mapLinks. Within each
  * CTxMemPoolEntry, we track the size and fees of all descendants.
  *
  * Usually when a new transaction is added to the mempool, it has no in-mempool
  * children (because any such children would be an orphan). So in
  * addUnchecked(), we:
  * - update a new entry's setMemPoolParents to include all in-mempool parents
  * - update the new entry's direct parents to include the new tx as a child
  * - update all ancestors of the transaction to include the new tx's size/fee
  *
  * When a transaction is removed from the mempool, we must:
  * - update all in-mempool parents to not track the tx in setMemPoolChildren
  * - update all ancestors to not include the tx's size/fees in descendant state
  * - update all in-mempool children to not include it as a parent
  *
  * These happen in UpdateForRemoveFromMempool(). (Note that when removing a
  * transaction along with its descendants, we must calculate that set of
  * transactions to be removed before doing the removal, or else the mempool can
  * be in an inconsistent state where it's impossible to walk the ancestors of a
  * transaction.)
  *
  * In the event of a reorg, the assumption that a newly added tx has no
  * in-mempool children is false.  In particular, the mempool is in an
  * inconsistent state while new transactions are being added, because there may
  * be descendant transactions of a tx coming from a disconnected block that are
  * unreachable from just looking at transactions in the mempool (the linking
  * transactions may also be in the disconnected block, waiting to be added).
  * Because of this, there's not much benefit in trying to search for in-mempool
  * children in addUnchecked(). Instead, in the special case of transactions
  * being added from a disconnected block, we require the caller to clean up the
  * state, to account for in-mempool, out-of-block descendants for all the
  * in-block transactions by calling UpdateTransactionsFromBlock(). Note that
  * until this is called, the mempool state is not consistent, and in particular
  * mapLinks may not be correct (and therefore functions like
  * CalculateMemPoolAncestors() and CalculateDescendants() that rely on them to
  * walk the mempool are not generally safe to use).
  *
  * Computational limits:
  *
  * Updating all in-mempool ancestors of a newly added transaction can be slow,
  * if no bound exists on how many in-mempool ancestors there may be.
  * CalculateMemPoolAncestors() takes configurable limits that are designed to
  * prevent these calculations from being too CPU intensive.
  */
 class CTxMemPool {
 private:
     //! Value n means that n times in 2^32 we check.
     uint32_t nCheckFrequency GUARDED_BY(cs);
     //! Used by getblocktemplate to trigger CreateNewBlock() invocation
     unsigned int nTransactionsUpdated;
 
     //! sum of all mempool tx's sizes.
     uint64_t totalTxSize;
     //! sum of dynamic memory usage of all the map elements (NOT the maps
     //! themselves)
     uint64_t cachedInnerUsage;
 
     mutable int64_t lastRollingFeeUpdate;
     mutable bool blockSinceLastRollingFeeBump;
     //! minimum fee to get into the pool, decreases exponentially
     mutable double rollingMinimumFeeRate;
 
     void trackPackageRemoved(const CFeeRate &rate) EXCLUSIVE_LOCKS_REQUIRED(cs);
 
     bool m_is_loaded GUARDED_BY(cs){false};
 
 public:
     // public only for testing
     static const int ROLLING_FEE_HALFLIFE = 60 * 60 * 12;
 
     typedef boost::multi_index_container<
         CTxMemPoolEntry, boost::multi_index::indexed_by<
                              // sorted by txid
                              boost::multi_index::hashed_unique<
                                  mempoolentry_txid, SaltedTxidHasher>,
                              // sorted by fee rate
                              boost::multi_index::ordered_non_unique<
                                  boost::multi_index::tag<descendant_score>,
                                  boost::multi_index::identity<CTxMemPoolEntry>,
                                  CompareTxMemPoolEntryByDescendantScore>,
                              // sorted by entry time
                              boost::multi_index::ordered_non_unique<
                                  boost::multi_index::tag<entry_time>,
                                  boost::multi_index::identity<CTxMemPoolEntry>,
                                  CompareTxMemPoolEntryByEntryTime>,
                              // sorted by fee rate with ancestors
                              boost::multi_index::ordered_non_unique<
                                  boost::multi_index::tag<ancestor_score>,
                                  boost::multi_index::identity<CTxMemPoolEntry>,
                                  CompareTxMemPoolEntryByAncestorFee>>>
         indexed_transaction_set;
 
     /**
      * This mutex needs to be locked when accessing `mapTx` or other members
      * that are guarded by it.
      *
      * @par Consistency guarantees
      *
      * By design, it is guaranteed that:
      *
      * 1. Locking both `cs_main` and `mempool.cs` will give a view of mempool
      *    that is consistent with current chain tip (`chainActive` and
      *    `pcoinsTip`) and is fully populated. Fully populated means that if the
      *    current active chain is missing transactions that were present in a
      *    previously active chain, all the missing transactions will have been
      *    re-added to the mempool and should be present if they meet size and
      *    consistency constraints.
      *
      * 2. Locking `mempool.cs` without `cs_main` will give a view of a mempool
      *    consistent with some chain that was active since `cs_main` was last
      *    locked, and that is fully populated as described above. It is ok for
      *    code that only needs to query or remove transactions from the mempool
      *    to lock just `mempool.cs` without `cs_main`.
      *
      * To provide these guarantees, it is necessary to lock both `cs_main` and
      * `mempool.cs` whenever adding transactions to the mempool and whenever
      * changing the chain tip. It's necessary to keep both mutexes locked until
      * the mempool is consistent with the new chain tip and fully populated.
      *
      * @par Consistency bug
      *
      * The second guarantee above is not currently enforced, but
      * https://github.com/bitcoin/bitcoin/pull/14193 will fix it. No known code
      * in bitcoin currently depends on second guarantee, but it is important to
      * fix for third party code that needs be able to frequently poll the
      * mempool without locking `cs_main` and without encountering missing
      * transactions during reorgs.
      */
     mutable RecursiveMutex cs;
     indexed_transaction_set mapTx GUARDED_BY(cs);
 
     typedef indexed_transaction_set::nth_index<0>::type::iterator txiter;
     //! All tx hashes/entries in mapTx, in random order
     std::vector<std::pair<TxHash, txiter>> vTxHashes;
 
     struct CompareIteratorById {
         bool operator()(const txiter &a, const txiter &b) const {
             return a->GetTx().GetId() < b->GetTx().GetId();
         }
     };
     typedef std::set<txiter, CompareIteratorById> setEntries;
 
     const setEntries &GetMemPoolParents(txiter entry) const
         EXCLUSIVE_LOCKS_REQUIRED(cs);
     const setEntries &GetMemPoolChildren(txiter entry) const
         EXCLUSIVE_LOCKS_REQUIRED(cs);
     uint64_t CalculateDescendantMaximum(txiter entry) const
         EXCLUSIVE_LOCKS_REQUIRED(cs);
 
 private:
     typedef std::map<txiter, setEntries, CompareIteratorById> cacheMap;
 
     struct TxLinks {
         setEntries parents;
         setEntries children;
     };
 
     typedef std::map<txiter, TxLinks, CompareIteratorById> txlinksMap;
     txlinksMap mapLinks;
 
     void UpdateParent(txiter entry, txiter parent, bool add);
     void UpdateChild(txiter entry, txiter child, bool add);
 
     std::vector<indexed_transaction_set::const_iterator>
     GetSortedDepthAndScore() const EXCLUSIVE_LOCKS_REQUIRED(cs);
 
 public:
     indirectmap<COutPoint, const CTransaction *> mapNextTx GUARDED_BY(cs);
     std::map<TxId, Amount> mapDeltas;
 
     /**
      * Create a new CTxMemPool.
      */
     CTxMemPool();
     ~CTxMemPool();
 
     /**
      * If sanity-checking is turned on, check makes sure the pool is consistent
      * (does not contain two transactions that spend the same inputs, all inputs
      * are in the mapNextTx array). If sanity-checking is turned off, check does
      * nothing.
      */
     void check(const CCoinsViewCache *pcoins) const;
     void setSanityCheck(double dFrequency = 1.0) {
         LOCK(cs);
         nCheckFrequency = static_cast<uint32_t>(dFrequency * 4294967295.0);
     }
 
     // addUnchecked must updated state for all ancestors of a given transaction,
     // to track size/count of descendant transactions. First version of
     // addUnchecked can be used to have it call CalculateMemPoolAncestors(), and
     // then invoke the second version.
     // Note that addUnchecked is ONLY called from ATMP outside of tests
     // and any other callers may break wallet's in-mempool tracking (due to
     // lack of CValidationInterface::TransactionAddedToMempool callbacks).
     void addUnchecked(const CTxMemPoolEntry &entry)
         EXCLUSIVE_LOCKS_REQUIRED(cs, cs_main);
     void addUnchecked(const CTxMemPoolEntry &entry, setEntries &setAncestors)
         EXCLUSIVE_LOCKS_REQUIRED(cs, cs_main);
 
     void removeRecursive(
         const CTransaction &tx,
         MemPoolRemovalReason reason = MemPoolRemovalReason::UNKNOWN);
     void removeForReorg(const Config &config, const CCoinsViewCache *pcoins,
                         unsigned int nMemPoolHeight, int flags)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
     void removeConflicts(const CTransaction &tx) EXCLUSIVE_LOCKS_REQUIRED(cs);
     void removeForBlock(const std::vector<CTransactionRef> &vtx,
                         unsigned int nBlockHeight);
 
     void clear();
     // lock free
     void _clear() EXCLUSIVE_LOCKS_REQUIRED(cs);
     bool CompareDepthAndScore(const TxId &txida, const TxId &txidb);
     void queryHashes(std::vector<uint256> &vtxid) const;
     bool isSpent(const COutPoint &outpoint) const;
     unsigned int GetTransactionsUpdated() const;
     void AddTransactionsUpdated(unsigned int n);
     /**
      * Check that none of this transactions inputs are in the mempool, and thus
      * the tx is not dependent on other mempool transactions to be included in a
      * block.
      */
     bool HasNoInputsOf(const CTransaction &tx) const;
 
     /** Affect CreateNewBlock prioritisation of transactions */
     void PrioritiseTransaction(const TxId &txid, const Amount nFeeDelta);
     void ApplyDelta(const TxId &txid, Amount &nFeeDelta) const;
     void ClearPrioritisation(const TxId &txid);
 
     /** Get the transaction in the pool that spends the same prevout */
     const CTransaction *GetConflictTx(const COutPoint &prevout) const
         EXCLUSIVE_LOCKS_REQUIRED(cs);
 
     /** Returns an iterator to the given txid, if found */
     boost::optional<txiter> GetIter(const TxId &txid) const
         EXCLUSIVE_LOCKS_REQUIRED(cs);
 
     /**
      * Translate a set of txids into a set of pool iterators to avoid repeated
      * lookups.
      */
     setEntries GetIterSet(const std::set<TxId> &txids) const
         EXCLUSIVE_LOCKS_REQUIRED(cs);
 
     /**
      * Remove a set of transactions from the mempool. If a transaction is in
      * this set, then all in-mempool descendants must also be in the set, unless
      * this transaction is being removed for being in a block. Set
      * updateDescendants to true when removing a tx that was in a block, so that
      * any in-mempool descendants have their ancestor state updated.
      */
     void
     RemoveStaged(setEntries &stage, bool updateDescendants,
                  MemPoolRemovalReason reason = MemPoolRemovalReason::UNKNOWN)
         EXCLUSIVE_LOCKS_REQUIRED(cs);
 
     /**
      * When adding transactions from a disconnected block back to the mempool,
      * new mempool entries may have children in the mempool (which is generally
      * not the case when otherwise adding transactions).
      * UpdateTransactionsFromBlock() will find child transactions and update the
      * descendant state for each transaction in txidsToUpdate (excluding any
      * child transactions present in txidsToUpdate, which are already accounted
      * for).
      * Note: txidsToUpdate should be the set of transactions from the
      * disconnected block that have been accepted back into the mempool.
      */
     void UpdateTransactionsFromBlock(const std::vector<TxId> &txidsToUpdate)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
     /**
      * Try to calculate all in-mempool ancestors of entry.
      *  (these are all calculated including the tx itself)
      *  limitAncestorCount = max number of ancestors
      *  limitAncestorSize = max size of ancestors
      *  limitDescendantCount = max number of descendants any ancestor can have
      *  limitDescendantSize = max size of descendants any ancestor can have
      *  errString = populated with error reason if any limits are hit
      * fSearchForParents = whether to search a tx's vin for in-mempool parents,
      * or look up parents from mapLinks. Must be true for entries not in the
      * mempool
      */
     bool CalculateMemPoolAncestors(
         const CTxMemPoolEntry &entry, setEntries &setAncestors,
         uint64_t limitAncestorCount, uint64_t limitAncestorSize,
         uint64_t limitDescendantCount, uint64_t limitDescendantSize,
         std::string &errString, bool fSearchForParents = true) const
         EXCLUSIVE_LOCKS_REQUIRED(cs);
 
     /**
      * Populate setDescendants with all in-mempool descendants of hash.
      * Assumes that setDescendants includes all in-mempool descendants of
      * anything already in it.
      */
     void CalculateDescendants(txiter it, setEntries &setDescendants) const
         EXCLUSIVE_LOCKS_REQUIRED(cs);
 
     /**
      * The minimum fee to get into the mempool, which may itself not be enough
      * for larger-sized transactions. The incrementalRelayFee policy variable is
      * used to bound the time it takes the fee rate to go back down all the way
      * to 0. When the feerate would otherwise be half of this, it is set to 0
      * instead.
      */
     CFeeRate GetMinFee(size_t sizelimit) const;
 
     /**
      * Remove transactions from the mempool until its dynamic size is <=
      * sizelimit. pvNoSpendsRemaining, if set, will be populated with the list
      * of outpoints which are not in mempool which no longer have any spends in
      * this mempool.
      */
     void TrimToSize(size_t sizelimit,
                     std::vector<COutPoint> *pvNoSpendsRemaining = nullptr);
 
     /**
      * Expire all transaction (and their dependencies) in the mempool older than
      * time. Return the number of removed transactions.
      */
     int Expire(int64_t time);
 
     /**
      * Reduce the size of the mempool by expiring and then trimming the mempool.
      */
     void LimitSize(size_t limit, unsigned long age);
 
     /**
      * Calculate the ancestor and descendant count for the given transaction.
      * The counts include the transaction itself.
      */
     void GetTransactionAncestry(const TxId &txid, size_t &ancestors,
                                 size_t &descendants) const;
 
     /** @returns true if the mempool is fully loaded */
     bool IsLoaded() const;
 
     /** Sets the current loaded state */
     void SetIsLoaded(bool loaded);
 
     unsigned long size() const {
         LOCK(cs);
         return mapTx.size();
     }
 
     uint64_t GetTotalTxSize() const {
         LOCK(cs);
         return totalTxSize;
     }
 
     bool exists(const TxId &txid) const {
         LOCK(cs);
         return mapTx.count(txid) != 0;
     }
 
     CTransactionRef get(const TxId &txid) const;
     TxMempoolInfo info(const TxId &txid) const;
     std::vector<TxMempoolInfo> infoAll() const;
 
     CFeeRate estimateFee() const;
 
     size_t DynamicMemoryUsage() const;
 
     boost::signals2::signal<void(CTransactionRef)> NotifyEntryAdded;
     boost::signals2::signal<void(CTransactionRef, MemPoolRemovalReason)>
         NotifyEntryRemoved;
 
 private:
     /**
      * UpdateForDescendants is used by UpdateTransactionsFromBlock to update the
      * descendants for a single transaction that has been added to the mempool
      * but may have child transactions in the mempool, eg during a chain reorg.
      * setExclude is the set of descendant transactions in the mempool that must
      * not be accounted for (because any descendants in setExclude were added to
      * the mempool after the transaction being updated and hence their state is
      * already reflected in the parent state).
      *
      * cachedDescendants will be updated with the descendants of the transaction
      * being updated, so that future invocations don't need to walk the same
      * transaction again, if encountered in another transaction chain.
      */
     void UpdateForDescendants(txiter updateIt, cacheMap &cachedDescendants,
                               const std::set<TxId> &setExclude)
         EXCLUSIVE_LOCKS_REQUIRED(cs);
     /**
      * Update ancestors of hash to add/remove it as a descendant transaction.
      */
     void UpdateAncestorsOf(bool add, txiter hash, setEntries &setAncestors)
         EXCLUSIVE_LOCKS_REQUIRED(cs);
     /** Set ancestor state for an entry */
     void UpdateEntryForAncestors(txiter it, const setEntries &setAncestors)
         EXCLUSIVE_LOCKS_REQUIRED(cs);
     /**
      * For each transaction being removed, update ancestors and any direct
      * children. If updateDescendants is true, then also update in-mempool
      * descendants' ancestor state.
      */
     void UpdateForRemoveFromMempool(const setEntries &entriesToRemove,
                                     bool updateDescendants)
         EXCLUSIVE_LOCKS_REQUIRED(cs);
     /** Sever link between specified transaction and direct children. */
     void UpdateChildrenForRemoval(txiter entry) EXCLUSIVE_LOCKS_REQUIRED(cs);
 
     /**
      * Before calling removeUnchecked for a given transaction,
      * UpdateForRemoveFromMempool must be called on the entire (dependent) set
      * of transactions being removed at the same time. We use each
      * CTxMemPoolEntry's setMemPoolParents in order to walk ancestors of a given
      * transaction that is removed, so we can't remove intermediate transactions
      * in a chain before we've updated all the state for the removal.
      */
     void
     removeUnchecked(txiter entry,
                     MemPoolRemovalReason reason = MemPoolRemovalReason::UNKNOWN)
         EXCLUSIVE_LOCKS_REQUIRED(cs);
 };
 
 /**
  * CCoinsView that brings transactions from a mempool into view.
  * It does not check for spendings by memory pool transactions.
  * Instead, it provides access to all Coins which are either unspent in the
  * base CCoinsView, or are outputs from any mempool transaction!
  * This allows transaction replacement to work as expected, as you want to
  * have all inputs "available" to check signatures, and any cycles in the
  * dependency graph are checked directly in AcceptToMemoryPool.
  * It also allows you to sign a double-spend directly in
  * signrawtransactionwithkey and signrawtransactionwithwallet,
  * as long as the conflicting transaction is not yet confirmed.
  */
 class CCoinsViewMemPool : public CCoinsViewBacked {
 protected:
     const CTxMemPool &mempool;
 
 public:
     CCoinsViewMemPool(CCoinsView *baseIn, const CTxMemPool &mempoolIn);
     bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
 };
 
 /**
  * DisconnectedBlockTransactions
  *
  * During the reorg, it's desirable to re-add previously confirmed transactions
  * to the mempool, so that anything not re-confirmed in the new chain is
  * available to be mined. However, it's more efficient to wait until the reorg
  * is complete and process all still-unconfirmed transactions at that time,
  * since we expect most confirmed transactions to (typically) still be
  * confirmed in the new chain, and re-accepting to the memory pool is expensive
  * (and therefore better to not do in the middle of reorg-processing).
  * Instead, store the disconnected transactions (in order!) as we go, remove any
  * that are included in blocks in the new chain, and then process the remaining
  * still-unconfirmed transactions at the end.
  *
  * It also enables efficient reprocessing of current mempool entries, useful
  * when (de)activating forks that result in in-mempool transactions becoming
  * invalid
  */
 // multi_index tag names
 struct txid_index {};
 struct insertion_order {};
 
 class DisconnectedBlockTransactions {
 private:
     typedef boost::multi_index_container<
         CTransactionRef, boost::multi_index::indexed_by<
                              // sorted by txid
                              boost::multi_index::hashed_unique<
                                  boost::multi_index::tag<txid_index>,
                                  mempoolentry_txid, SaltedTxidHasher>,
                              // sorted by order in the blockchain
                              boost::multi_index::sequenced<
                                  boost::multi_index::tag<insertion_order>>>>
         indexed_disconnected_transactions;
 
     indexed_disconnected_transactions queuedTx;
     uint64_t cachedInnerUsage = 0;
 
     void addTransaction(const CTransactionRef &tx) {
         queuedTx.insert(tx);
         cachedInnerUsage += RecursiveDynamicUsage(tx);
     }
 
 public:
     // It's almost certainly a logic bug if we don't clear out queuedTx before
     // destruction, as we add to it while disconnecting blocks, and then we
     // need to re-process remaining transactions to ensure mempool consistency.
     // For now, assert() that we've emptied out this object on destruction.
     // This assert() can always be removed if the reorg-processing code were
     // to be refactored such that this assumption is no longer true (for
     // instance if there was some other way we cleaned up the mempool after a
     // reorg, besides draining this object).
     ~DisconnectedBlockTransactions() { assert(queuedTx.empty()); }
 
     // Estimate the overhead of queuedTx to be 6 pointers + an allocation, as
     // no exact formula for boost::multi_index_contained is implemented.
     size_t DynamicMemoryUsage() const {
         return memusage::MallocUsage(sizeof(CTransactionRef) +
                                      6 * sizeof(void *)) *
                    queuedTx.size() +
                cachedInnerUsage;
     }
 
     const indexed_disconnected_transactions &GetQueuedTx() const {
         return queuedTx;
     }
 
     // Import mempool entries in topological order into queuedTx and clear the
     // mempool. Caller should call updateMempoolForReorg to reprocess these
     // transactions
     void importMempool(CTxMemPool &pool);
 
     // Add entries for a block while reconstructing the topological ordering so
     // they can be added back to the mempool simply.
     void addForBlock(const std::vector<CTransactionRef> &vtx);
 
     // Remove entries based on txid_index, and update memory usage.
     void removeForBlock(const std::vector<CTransactionRef> &vtx) {
         // Short-circuit in the common case of a block being added to the tip
         if (queuedTx.empty()) {
             return;
         }
         for (auto const &tx : vtx) {
             auto it = queuedTx.find(tx->GetId());
             if (it != queuedTx.end()) {
                 cachedInnerUsage -= RecursiveDynamicUsage(*it);
                 queuedTx.erase(it);
             }
         }
     }
 
     // Remove an entry by insertion_order index, and update memory usage.
     void removeEntry(indexed_disconnected_transactions::index<
                      insertion_order>::type::iterator entry) {
         cachedInnerUsage -= RecursiveDynamicUsage(*entry);
         queuedTx.get<insertion_order>().erase(entry);
     }
 
     bool isEmpty() const { return queuedTx.empty(); }
 
     void clear() {
         cachedInnerUsage = 0;
         queuedTx.clear();
     }
 
     /**
      * Make mempool consistent after a reorg, by re-adding or recursively
      * erasing disconnected block transactions from the mempool, and also
      * removing any other transactions from the mempool that are no longer valid
      * given the new tip/height.
      *
      * Note: we assume that disconnectpool only contains transactions that are
      * NOT confirmed in the current chain nor already in the mempool (otherwise,
      * in-mempool descendants of such transactions would be removed).
      *
      * Passing fAddToMempool=false will skip trying to add the transactions
      * back, and instead just erase from the mempool as needed.
      */
     void updateMempoolForReorg(const Config &config, bool fAddToMempool);
 };
 
 #endif // BITCOIN_TXMEMPOOL_H
diff --git a/src/validation.cpp b/src/validation.cpp
index 6b0822bcd4..2d5fd3d895 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1,5820 +1,5854 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
 // Copyright (c) 2009-2018 The Bitcoin Core developers
 // Copyright (c) 2017-2020 The Bitcoin developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <validation.h>
 
 #include <arith_uint256.h>
 #include <blockindexworkcomparator.h>
 #include <blockvalidity.h>
 #include <chainparams.h>
 #include <checkpoints.h>
 #include <checkqueue.h>
 #include <config.h>
 #include <consensus/activation.h>
 #include <consensus/consensus.h>
 #include <consensus/merkle.h>
 #include <consensus/tx_verify.h>
 #include <consensus/validation.h>
 #include <flatfile.h>
 #include <fs.h>
 #include <hash.h>
 #include <index/txindex.h>
 #include <policy/fees.h>
 #include <policy/mempool.h>
 #include <policy/policy.h>
 #include <pow.h>
 #include <primitives/block.h>
 #include <primitives/transaction.h>
 #include <random.h>
 #include <reverse_iterator.h>
 #include <script/script.h>
 #include <script/scriptcache.h>
 #include <script/sigcache.h>
 #include <script/standard.h>
 #include <shutdown.h>
 #include <timedata.h>
 #include <tinyformat.h>
 #include <txdb.h>
 #include <txmempool.h>
 #include <ui_interface.h>
 #include <undo.h>
 #include <util/moneystr.h>
 #include <util/strencodings.h>
 #include <util/system.h>
 #include <validationinterface.h>
 #include <warnings.h>
 
 #include <boost/algorithm/string/replace.hpp>
 #include <boost/thread.hpp> // boost::this_thread::interruption_point() (mingw)
 
 #include <atomic>
 #include <future>
 #include <sstream>
 #include <thread>
 
 #define MICRO 0.000001
 #define MILLI 0.001
 class ConnectTrace;
 
 /**
  * CChainState stores and provides an API to update our local knowledge of the
  * current best chain and header tree.
  *
  * It generally provides access to the current block tree, as well as functions
  * to provide new data, which it will appropriately validate and incorporate in
  * its state as necessary.
  *
  * Eventually, the API here is targeted at being exposed externally as a
  * consumable libconsensus library, so any functions added must only call
  * other class member functions, pure functions in other parts of the consensus
  * library, callbacks via the validation interface, or read/write-to-disk
  * functions (eventually this will also be via callbacks).
  */
 class CChainState {
 private:
     /**
      * The set of all CBlockIndex entries with BLOCK_VALID_TRANSACTIONS (for
      * itself and all ancestors) and as good as our current tip or better.
      * Entries may be failed or parked though, and pruning nodes may be missing
      * the data for the block; these will get cleaned during FindMostWorkChain.
      */
     std::set<CBlockIndex *, CBlockIndexWorkComparator> setBlockIndexCandidates;
 
     /**
      * the ChainState CriticalSection
      * A lock that must be held when modifying this ChainState - held in
      * ActivateBestChain()
      */
     CCriticalSection m_cs_chainstate;
 
     /**
      * Every received block is assigned a unique and increasing identifier, so
      * we know which one to give priority in case of a fork.
      * Blocks loaded from disk are assigned id 0, so start the counter at 1.
      */
     std::atomic<int32_t> nBlockSequenceId{1};
     /** Decreasing counter (used by subsequent preciousblock calls). */
     int32_t nBlockReverseSequenceId = -1;
     /** chainwork for the last block that preciousblock has been applied to. */
     arith_uint256 nLastPreciousChainwork = 0;
 
     /**
      * In order to efficiently track invalidity of headers, we keep the set of
      * blocks which we tried to connect and found to be invalid here (ie which
      * were set to BLOCK_FAILED_VALID since the last restart). We can then
      * walk this set and check if a new header is a descendant of something in
      * this set, preventing us from having to walk mapBlockIndex when we try
      * to connect a bad block and fail.
      *
      * While this is more complicated than marking everything which descends
      * from an invalid block as invalid at the time we discover it to be
      * invalid, doing so would require walking all of mapBlockIndex to find all
      * descendants. Since this case should be very rare, keeping track of all
      * BLOCK_FAILED_VALID blocks in a set should be just fine and work just as
      * well.
      *
      * Because we already walk mapBlockIndex in height-order at startup, we go
      * ahead and mark descendants of invalid blocks as FAILED_CHILD at that
      * time, instead of putting things in this set.
      */
     std::set<CBlockIndex *> m_failed_blocks;
 
 public:
     CChain chainActive;
     BlockMap mapBlockIndex GUARDED_BY(cs_main);
     std::multimap<CBlockIndex *, CBlockIndex *> mapBlocksUnlinked;
     CBlockIndex *pindexBestInvalid = nullptr;
     CBlockIndex *pindexBestParked = nullptr;
     CBlockIndex const *pindexFinalized = nullptr;
 
     bool LoadBlockIndex(const Config &config, CBlockTreeDB &blocktree)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
     bool ActivateBestChain(
         const Config &config, CValidationState &state,
         std::shared_ptr<const CBlock> pblock = std::shared_ptr<const CBlock>());
 
     /**
      * If a block header hasn't already been seen, call CheckBlockHeader on it,
      * ensure that it doesn't descend from an invalid block, and then add it to
      * mapBlockIndex.
      */
     bool AcceptBlockHeader(const Config &config, const CBlockHeader &block,
                            CValidationState &state, CBlockIndex **ppindex)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
     bool AcceptBlock(const Config &config,
                      const std::shared_ptr<const CBlock> &pblock,
                      CValidationState &state, bool fRequested,
                      const FlatFilePos *dbp, bool *fNewBlock)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
     // Block (dis)connection on a given view:
     DisconnectResult DisconnectBlock(const CBlock &block,
                                      const CBlockIndex *pindex,
                                      CCoinsViewCache &view);
     bool ConnectBlock(const CBlock &block, CValidationState &state,
                       CBlockIndex *pindex, CCoinsViewCache &view,
                       const CChainParams &params,
                       BlockValidationOptions options, bool fJustCheck = false)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
     // Block disconnection on our pcoinsTip:
     bool DisconnectTip(const Config &config, CValidationState &state,
                        DisconnectedBlockTransactions *disconnectpool)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
     // Manual block validity manipulation:
     bool PreciousBlock(const Config &config, CValidationState &state,
                        CBlockIndex *pindex) LOCKS_EXCLUDED(cs_main);
     bool UnwindBlock(const Config &config, CValidationState &state,
                      CBlockIndex *pindex, bool invalidate);
     void ResetBlockFailureFlags(CBlockIndex *pindex)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
     template <typename F>
     void UpdateFlagsForBlock(CBlockIndex *pindexBase, CBlockIndex *pindex, F f)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
     template <typename F, typename C>
     void UpdateFlags(CBlockIndex *pindex, F f, C fchild)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
     template <typename F>
     void UpdateFlags(CBlockIndex *pindex, F f)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
     /** Remove parked status from a block and its descendants. */
     void UnparkBlockImpl(CBlockIndex *pindex, bool fClearChildren)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
     bool ReplayBlocks(const Consensus::Params &params, CCoinsView *view);
     bool LoadGenesisBlock(const CChainParams &chainparams);
 
     void PruneBlockIndexCandidates();
 
     void UnloadBlockIndex();
 
 private:
     bool ActivateBestChainStep(const Config &config, CValidationState &state,
                                CBlockIndex *pindexMostWork,
                                const std::shared_ptr<const CBlock> &pblock,
                                bool &fInvalidFound, ConnectTrace &connectTrace)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
     bool ConnectTip(const Config &config, CValidationState &state,
                     CBlockIndex *pindexNew,
                     const std::shared_ptr<const CBlock> &pblock,
                     ConnectTrace &connectTrace,
                     DisconnectedBlockTransactions &disconnectpool)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
     CBlockIndex *AddToBlockIndex(const CBlockHeader &block)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
     /** Create a new block index entry for a given block hash */
     CBlockIndex *InsertBlockIndex(const BlockHash &hash)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
     /**
      * Make various assertions about the state of the block index.
      *
      * By default this only executes fully when using the Regtest chain; see:
      * fCheckBlockIndex.
      */
     void CheckBlockIndex(const Consensus::Params &consensusParams);
 
     void InvalidBlockFound(CBlockIndex *pindex, const CValidationState &state)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
     CBlockIndex *FindMostWorkChain() EXCLUSIVE_LOCKS_REQUIRED(cs_main);
     void ReceivedBlockTransactions(const CBlock &block, CBlockIndex *pindexNew,
                                    const FlatFilePos &pos)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
     bool RollforwardBlock(const CBlockIndex *pindex, CCoinsViewCache &inputs,
                           const Consensus::Params &params)
         EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 } g_chainstate;
 
 /**
  * Global state
  *
  * Mutex to guard access to validation specific variables, such as reading
  * or changing the chainstate.
  *
  * This may also need to be locked when updating the transaction pool, e.g. on
  * AcceptToMemoryPool. See CTxMemPool::cs comment for details.
  *
  * The transaction pool has a separate lock to allow reading from it and the
  * chainstate at the same time.
  */
 RecursiveMutex cs_main;
 
 BlockMap &mapBlockIndex = g_chainstate.mapBlockIndex;
 CChain &chainActive = g_chainstate.chainActive;
 CBlockIndex *pindexBestHeader = nullptr;
 Mutex g_best_block_mutex;
 std::condition_variable g_best_block_cv;
 uint256 g_best_block;
 int nScriptCheckThreads = 0;
 std::atomic_bool fImporting(false);
 std::atomic_bool fReindex(false);
 bool fHavePruned = false;
 bool fPruneMode = false;
 bool fIsBareMultisigStd = DEFAULT_PERMIT_BAREMULTISIG;
 bool fRequireStandard = true;
 bool fCheckBlockIndex = false;
 bool fCheckpointsEnabled = DEFAULT_CHECKPOINTS_ENABLED;
 size_t nCoinCacheUsage = 5000 * 300;
 uint64_t nPruneTarget = 0;
 int64_t nMaxTipAge = DEFAULT_MAX_TIP_AGE;
 
 BlockHash hashAssumeValid;
 arith_uint256 nMinimumChainWork;
 
 CFeeRate minRelayTxFee = CFeeRate(DEFAULT_MIN_RELAY_TX_FEE_PER_KB);
 Amount maxTxFee = DEFAULT_TRANSACTION_MAXFEE;
 
 CTxMemPool g_mempool;
 
 /** Constant stuff for coinbase transactions we create: */
 CScript COINBASE_FLAGS;
 
 const std::string strMessageMagic = "Bitcoin Signed Message:\n";
 
 // Internal stuff
 namespace {
 CBlockIndex *&pindexBestInvalid = g_chainstate.pindexBestInvalid;
 CBlockIndex *&pindexBestParked = g_chainstate.pindexBestParked;
 
 /**
  * The best finalized block.
  * This block cannot be reorged in any way, shape or form.
  */
 CBlockIndex const *&pindexFinalized = g_chainstate.pindexFinalized;
 
 /**
  * All pairs A->B, where A (or one of its ancestors) misses transactions, but B
  * has transactions. Pruned nodes may have entries where B is missing data.
  */
 std::multimap<CBlockIndex *, CBlockIndex *> &mapBlocksUnlinked =
     g_chainstate.mapBlocksUnlinked;
 
 CCriticalSection cs_LastBlockFile;
 std::vector<CBlockFileInfo> vinfoBlockFile;
 int nLastBlockFile = 0;
 /**
  * Global flag to indicate we should check to see if there are block/undo files
  * that should be deleted. Set on startup or if we allocate more file space when
  * we're in prune mode.
  */
 bool fCheckForPruning = false;
 
 /** Dirty block index entries. */
 std::set<const CBlockIndex *> setDirtyBlockIndex;
 
 /** Dirty block file entries. */
 std::set<int> setDirtyFileInfo;
 } // namespace
 
 BlockValidationOptions::BlockValidationOptions(const Config &config)
     : excessiveBlockSize(config.GetMaxBlockSize()), checkPoW(true),
       checkMerkleRoot(true) {}
 
 CBlockIndex *FindForkInGlobalIndex(const CChain &chain,
                                    const CBlockLocator &locator) {
     AssertLockHeld(cs_main);
 
     // Find the first block the caller has in the main chain
     for (const BlockHash &hash : locator.vHave) {
         CBlockIndex *pindex = LookupBlockIndex(hash);
         if (pindex) {
             if (chain.Contains(pindex)) {
                 return pindex;
             }
             if (pindex->GetAncestor(chain.Height()) == chain.Tip()) {
                 return chain.Tip();
             }
         }
     }
     return chain.Genesis();
 }
 
 std::unique_ptr<CCoinsViewDB> pcoinsdbview;
 std::unique_ptr<CCoinsViewCache> pcoinsTip;
 std::unique_ptr<CBlockTreeDB> pblocktree;
 
 enum class FlushStateMode { NONE, IF_NEEDED, PERIODIC, ALWAYS };
 
 // See definition for documentation
 static bool FlushStateToDisk(const CChainParams &chainParams,
                              CValidationState &state, FlushStateMode mode,
                              int nManualPruneHeight = 0);
 static void FindFilesToPruneManual(std::set<int> &setFilesToPrune,
                                    int nManualPruneHeight);
 static void FindFilesToPrune(std::set<int> &setFilesToPrune,
                              uint64_t nPruneAfterHeight);
 static FILE *OpenUndoFile(const FlatFilePos &pos, bool fReadOnly = false);
 static FlatFileSeq BlockFileSeq();
 static FlatFileSeq UndoFileSeq();
 static uint32_t GetNextBlockScriptFlags(const Consensus::Params &params,
                                         const CBlockIndex *pindex);
 
 bool TestLockPointValidity(const LockPoints *lp) {
     AssertLockHeld(cs_main);
     assert(lp);
     // If there are relative lock times then the maxInputBlock will be set
     // If there are no relative lock times, the LockPoints don't depend on the
     // chain
     if (lp->maxInputBlock) {
         // Check whether chainActive is an extension of the block at which the
         // LockPoints calculation was valid. If not LockPoints are no longer
         // valid.
         if (!chainActive.Contains(lp->maxInputBlock)) {
             return false;
         }
     }
 
     // LockPoints still valid
     return true;
 }
 
 bool CheckSequenceLocks(const CTxMemPool &pool, const CTransaction &tx,
                         int flags, LockPoints *lp, bool useExistingLockPoints) {
     AssertLockHeld(cs_main);
     AssertLockHeld(pool.cs);
 
     CBlockIndex *tip = chainActive.Tip();
     assert(tip != nullptr);
 
     CBlockIndex index;
     index.pprev = tip;
     // CheckSequenceLocks() uses chainActive.Height()+1 to evaluate height based
     // locks because when SequenceLocks() is called within ConnectBlock(), the
     // height of the block *being* evaluated is what is used. Thus if we want to
     // know if a transaction can be part of the *next* block, we need to use one
     // more than chainActive.Height()
     index.nHeight = tip->nHeight + 1;
 
     std::pair<int, int64_t> lockPair;
     if (useExistingLockPoints) {
         assert(lp);
         lockPair.first = lp->height;
         lockPair.second = lp->time;
     } else {
         // pcoinsTip contains the UTXO set for chainActive.Tip()
         CCoinsViewMemPool viewMemPool(pcoinsTip.get(), pool);
         std::vector<int> prevheights;
         prevheights.resize(tx.vin.size());
         for (size_t txinIndex = 0; txinIndex < tx.vin.size(); txinIndex++) {
             const CTxIn &txin = tx.vin[txinIndex];
             Coin coin;
             if (!viewMemPool.GetCoin(txin.prevout, coin)) {
                 return error("%s: Missing input", __func__);
             }
             if (coin.GetHeight() == MEMPOOL_HEIGHT) {
                 // Assume all mempool transaction confirm in the next block
                 prevheights[txinIndex] = tip->nHeight + 1;
             } else {
                 prevheights[txinIndex] = coin.GetHeight();
             }
         }
         lockPair = CalculateSequenceLocks(tx, flags, &prevheights, index);
         if (lp) {
             lp->height = lockPair.first;
             lp->time = lockPair.second;
             // Also store the hash of the block with the highest height of all
             // the blocks which have sequence locked prevouts. This hash needs
             // to still be on the chain for these LockPoint calculations to be
             // valid.
             // Note: It is impossible to correctly calculate a maxInputBlock if
             // any of the sequence locked inputs depend on unconfirmed txs,
             // except in the special case where the relative lock time/height is
             // 0, which is equivalent to no sequence lock. Since we assume input
             // height of tip+1 for mempool txs and test the resulting lockPair
             // from CalculateSequenceLocks against tip+1. We know
             // EvaluateSequenceLocks will fail if there was a non-zero sequence
             // lock on a mempool input, so we can use the return value of
             // CheckSequenceLocks to indicate the LockPoints validity.
             int maxInputHeight = 0;
             for (const int height : prevheights) {
                 // Can ignore mempool inputs since we'll fail if they had
                 // non-zero locks.
                 if (height != tip->nHeight + 1) {
                     maxInputHeight = std::max(maxInputHeight, height);
                 }
             }
             lp->maxInputBlock = tip->GetAncestor(maxInputHeight);
         }
     }
     return EvaluateSequenceLocks(index, lockPair);
 }
 
 /** Convert CValidationState to a human-readable message for logging */
 std::string FormatStateMessage(const CValidationState &state) {
     return strprintf(
         "%s%s (code %i)", state.GetRejectReason(),
         state.GetDebugMessage().empty() ? "" : ", " + state.GetDebugMessage(),
         state.GetRejectCode());
 }
 
 // Command-line argument "-replayprotectionactivationtime=<timestamp>" will
 // cause the node to switch to replay protected SigHash ForkID value when the
 // median timestamp of the previous 11 blocks is greater than or equal to
 // <timestamp>. Defaults to the pre-defined timestamp when not set.
 static bool IsReplayProtectionEnabled(const Consensus::Params &params,
                                       int64_t nMedianTimePast) {
     return nMedianTimePast >= gArgs.GetArg("-replayprotectionactivationtime",
                                            params.phononActivationTime);
 }
 
 static bool IsReplayProtectionEnabled(const Consensus::Params &params,
                                       const CBlockIndex *pindexPrev) {
     if (pindexPrev == nullptr) {
         return false;
     }
 
     return IsReplayProtectionEnabled(params, pindexPrev->GetMedianTimePast());
 }
 
 // Returns the script flags which should be checked for mempool admission when
 // the tip is at the given block.
 static uint32_t GetStandardScriptFlags(const Consensus::Params &params,
                                        const CBlockIndex *pindexTip) {
     // Use the consensus flags for the next block as a basis, and mix in the
     // declared-standard flags.
     uint32_t flags = GetNextBlockScriptFlags(params, pindexTip) |
                      STANDARD_SCRIPT_VERIFY_FLAGS;
 
     // Disable input sigchecks limit for mempool admission, prior to its
     // proper activation.
     flags &= ~SCRIPT_VERIFY_INPUT_SIGCHECKS;
 
     if (IsPhononEnabled(params, pindexTip)) {
         flags |= SCRIPT_VERIFY_INPUT_SIGCHECKS;
     }
 
     return flags;
 }
 
 // Used to avoid mempool polluting consensus critical paths if CCoinsViewMempool
 // were somehow broken and returning the wrong scriptPubKeys
 static bool CheckInputsFromMempoolAndCache(
     const CTransaction &tx, CValidationState &state,
     const CCoinsViewCache &view, const CTxMemPool &pool, const uint32_t flags,
     bool cacheSigStore, PrecomputedTransactionData &txdata, int &nSigChecksOut)
     EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
     AssertLockHeld(cs_main);
 
     // pool.cs should be locked already, but go ahead and re-take the lock here
     // to enforce that mempool doesn't change between when we check the view and
     // when we actually call through to CheckInputs
     LOCK(pool.cs);
 
     assert(!tx.IsCoinBase());
     for (const CTxIn &txin : tx.vin) {
         const Coin &coin = view.AccessCoin(txin.prevout);
 
         // At this point we haven't actually checked if the coins are all
         // available (or shouldn't assume we have, since CheckInputs does). So
         // we just return failure if the inputs are not available here, and then
         // only have to check equivalence for available inputs.
         if (coin.IsSpent()) {
             return false;
         }
 
         const CTransactionRef &txFrom = pool.get(txin.prevout.GetTxId());
         if (txFrom) {
             assert(txFrom->GetId() == txin.prevout.GetTxId());
             assert(txFrom->vout.size() > txin.prevout.GetN());
             assert(txFrom->vout[txin.prevout.GetN()] == coin.GetTxOut());
         } else {
             const Coin &coinFromDisk = pcoinsTip->AccessCoin(txin.prevout);
             assert(!coinFromDisk.IsSpent());
             assert(coinFromDisk.GetTxOut() == coin.GetTxOut());
         }
     }
 
     return CheckInputs(tx, state, view, true, flags, cacheSigStore, true,
                        txdata, nSigChecksOut);
 }
 
 static bool
 AcceptToMemoryPoolWorker(const Config &config, CTxMemPool &pool,
                          CValidationState &state, const CTransactionRef &ptx,
                          bool *pfMissingInputs, int64_t nAcceptTime,
                          bool bypass_limits, const Amount nAbsurdFee,
                          std::vector<COutPoint> &coins_to_uncache,
                          bool test_accept) EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
     AssertLockHeld(cs_main);
 
     const Consensus::Params &consensusParams =
         config.GetChainParams().GetConsensus();
 
     const CTransaction &tx = *ptx;
     const TxId txid = tx.GetId();
 
     // mempool "read lock" (held through
     // GetMainSignals().TransactionAddedToMempool())
     LOCK(pool.cs);
     if (pfMissingInputs) {
         *pfMissingInputs = false;
     }
 
     // Coinbase is only valid in a block, not as a loose transaction.
     if (!CheckRegularTransaction(tx, state)) {
         // state filled in by CheckRegularTransaction.
         return false;
     }
 
     // Rather not work on nonstandard transactions (unless -testnet/-regtest)
     std::string reason;
     if (fRequireStandard && !IsStandardTx(tx, reason)) {
         return state.DoS(0, false, REJECT_NONSTANDARD, reason);
     }
 
     // Only accept nLockTime-using transactions that can be mined in the next
     // block; we don't want our mempool filled up with transactions that can't
     // be mined yet.
     CValidationState ctxState;
     if (!ContextualCheckTransactionForCurrentBlock(
             consensusParams, tx, ctxState, STANDARD_LOCKTIME_VERIFY_FLAGS)) {
         // We copy the state from a dummy to ensure we don't increase the
         // ban score of peer for transaction that could be valid in the future.
         return state.DoS(
             0, false, REJECT_NONSTANDARD, ctxState.GetRejectReason(),
             ctxState.CorruptionPossible(), ctxState.GetDebugMessage());
     }
 
     // Is it already in the memory pool?
     if (pool.exists(txid)) {
         return state.Invalid(false, REJECT_DUPLICATE, "txn-already-in-mempool");
     }
 
     // Check for conflicts with in-memory transactions
     for (const CTxIn &txin : tx.vin) {
         auto itConflicting = pool.mapNextTx.find(txin.prevout);
         if (itConflicting != pool.mapNextTx.end()) {
             // Disable replacement feature for good
             return state.Invalid(false, REJECT_DUPLICATE,
                                  "txn-mempool-conflict");
         }
     }
 
     {
         CCoinsView dummy;
         CCoinsViewCache view(&dummy);
 
         LockPoints lp;
         CCoinsViewMemPool viewMemPool(pcoinsTip.get(), pool);
         view.SetBackend(viewMemPool);
 
         // Do all inputs exist?
         for (const CTxIn &txin : tx.vin) {
             if (!pcoinsTip->HaveCoinInCache(txin.prevout)) {
                 coins_to_uncache.push_back(txin.prevout);
             }
 
             if (!view.HaveCoin(txin.prevout)) {
                 // Are inputs missing because we already have the tx?
                 for (size_t out = 0; out < tx.vout.size(); out++) {
                     // Optimistically just do efficient check of cache for
                     // outputs.
                     if (pcoinsTip->HaveCoinInCache(COutPoint(txid, out))) {
                         return state.Invalid(false, REJECT_DUPLICATE,
                                              "txn-already-known");
                     }
                 }
 
                 // Otherwise assume this might be an orphan tx for which we just
                 // haven't seen parents yet.
                 if (pfMissingInputs) {
                     *pfMissingInputs = true;
                 }
 
                 // fMissingInputs and !state.IsInvalid() is used to detect this
                 // condition, don't set state.Invalid()
                 return false;
             }
         }
 
         // Are the actual inputs available?
         if (!view.HaveInputs(tx)) {
             return state.Invalid(false, REJECT_DUPLICATE,
                                  "bad-txns-inputs-spent");
         }
 
         // Bring the best block into scope.
         view.GetBestBlock();
 
         // We have all inputs cached now, so switch back to dummy, so we don't
         // need to keep lock on mempool.
         view.SetBackend(dummy);
 
         // Only accept BIP68 sequence locked transactions that can be mined in
         // the next block; we don't want our mempool filled up with transactions
         // that can't be mined yet. Must keep pool.cs for this unless we change
         // CheckSequenceLocks to take a CoinsViewCache instead of create its
         // own.
         if (!CheckSequenceLocks(pool, tx, STANDARD_LOCKTIME_VERIFY_FLAGS,
                                 &lp)) {
             return state.DoS(0, false, REJECT_NONSTANDARD, "non-BIP68-final");
         }
 
         Amount nFees = Amount::zero();
         if (!Consensus::CheckTxInputs(tx, state, view, GetSpendHeight(view),
                                       nFees)) {
             return error("%s: Consensus::CheckTxInputs: %s, %s", __func__,
                          tx.GetId().ToString(), FormatStateMessage(state));
         }
 
         const uint32_t nextBlockScriptVerifyFlags =
             GetNextBlockScriptFlags(consensusParams, chainActive.Tip());
 
         // Check for non-standard pay-to-script-hash in inputs
         if (fRequireStandard &&
             !AreInputsStandard(tx, view, nextBlockScriptVerifyFlags)) {
             return state.Invalid(false, REJECT_NONSTANDARD,
                                  "bad-txns-nonstandard-inputs");
         }
 
         // nModifiedFees includes any fee deltas from PrioritiseTransaction
         Amount nModifiedFees = nFees;
         pool.ApplyDelta(txid, nModifiedFees);
 
         // Keep track of transactions that spend a coinbase, which we re-scan
         // during reorgs to ensure COINBASE_MATURITY is still met.
         bool fSpendsCoinbase = false;
         for (const CTxIn &txin : tx.vin) {
             const Coin &coin = view.AccessCoin(txin.prevout);
             if (coin.IsCoinBase()) {
                 fSpendsCoinbase = true;
                 break;
             }
         }
         auto nSigOpsCount =
             GetTransactionSigOpCount(tx, view, nextBlockScriptVerifyFlags);
 
         // Check that the transaction doesn't have an excessive number of
         // sigops.
         static_assert(MAX_STANDARD_TX_SIGOPS <= MAX_TX_SIGOPS_COUNT,
                       "we don't want transactions we can't even mine");
         if (nSigOpsCount > MAX_STANDARD_TX_SIGOPS) {
             return state.DoS(0, false, REJECT_NONSTANDARD,
                              "bad-txns-too-many-sigops", false,
                              strprintf("%d", nSigOpsCount));
         }
 
         unsigned int nSize = tx.GetTotalSize();
 
         // No transactions are allowed below minRelayTxFee except from
         // disconnected blocks.
         // Do not change this to use virtualsize without coordinating a network
         // policy upgrade.
         if (!bypass_limits && nModifiedFees < minRelayTxFee.GetFee(nSize)) {
             return state.DoS(0, false, REJECT_INSUFFICIENTFEE,
                              "min relay fee not met");
         }
 
         if (nAbsurdFee != Amount::zero() && nFees > nAbsurdFee) {
             return state.Invalid(false, REJECT_HIGHFEE, "absurdly-high-fee",
                                  strprintf("%d > %d", nFees, nAbsurdFee));
         }
 
         // Validate input scripts against standard script flags.
         const uint32_t scriptVerifyFlags =
             GetStandardScriptFlags(consensusParams, chainActive.Tip());
         PrecomputedTransactionData txdata(tx);
         int nSigChecksStandard;
         if (!CheckInputs(tx, state, view, true, scriptVerifyFlags, true, false,
                          txdata, nSigChecksStandard)) {
             // State filled in by CheckInputs.
             return false;
         }
 
+        // After the sigchecks activation we repurpose the 'sigops' tracking in
+        // mempool/mining to actually track sigchecks instead. (Proper SigOps
+        // will not need to be counted any more since it's getting deactivated.)
+        auto nSigChecksOrOps =
+            (nextBlockScriptVerifyFlags & SCRIPT_REPORT_SIGCHECKS)
+                ? nSigChecksStandard
+                : nSigOpsCount;
+
         CTxMemPoolEntry entry(ptx, nFees, nAcceptTime, chainActive.Height(),
-                              fSpendsCoinbase, nSigOpsCount, lp);
+                              fSpendsCoinbase, nSigChecksOrOps, lp);
 
         unsigned int nVirtualSize = entry.GetTxVirtualSize();
 
         Amount mempoolRejectFee =
             pool.GetMinFee(
                     gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) *
                     1000000)
                 .GetFee(nVirtualSize);
         if (!bypass_limits && mempoolRejectFee > Amount::zero() &&
             nModifiedFees < mempoolRejectFee) {
             return state.DoS(
                 0, false, REJECT_INSUFFICIENTFEE, "mempool min fee not met",
                 false, strprintf("%d < %d", nModifiedFees, mempoolRejectFee));
         }
 
         // Calculate in-mempool ancestors, up to a limit.
         CTxMemPool::setEntries setAncestors;
         size_t nLimitAncestors = gArgs.GetArg(
             "-limitancestorcount",
             GetDefaultAncestorLimit(consensusParams, chainActive.Tip()));
         size_t nLimitAncestorSize =
             gArgs.GetArg("-limitancestorsize", DEFAULT_ANCESTOR_SIZE_LIMIT) *
             1000;
         size_t nLimitDescendants = gArgs.GetArg(
             "-limitdescendantcount",
             GetDefaultDescendantLimit(consensusParams, chainActive.Tip()));
         size_t nLimitDescendantSize =
             gArgs.GetArg("-limitdescendantsize",
                          DEFAULT_DESCENDANT_SIZE_LIMIT) *
             1000;
         std::string errString;
         if (!pool.CalculateMemPoolAncestors(
                 entry, setAncestors, nLimitAncestors, nLimitAncestorSize,
                 nLimitDescendants, nLimitDescendantSize, errString)) {
             return state.DoS(0, false, REJECT_NONSTANDARD,
                              "too-long-mempool-chain", false, errString);
         }
 
         // Check again against the next block's script verification flags
         // to cache our script execution flags.
         //
         // This is also useful in case of bugs in the standard flags that cause
         // transactions to pass as valid when they're actually invalid. For
         // instance the STRICTENC flag was incorrectly allowing certain CHECKSIG
         // NOT scripts to pass, even though they were invalid.
         //
         // There is a similar check in CreateNewBlock() to prevent creating
         // invalid blocks (using TestBlockValidity), however allowing such
         // transactions into the mempool can be exploited as a DoS attack.
         int nSigChecksConsensus;
         if (!CheckInputsFromMempoolAndCache(tx, state, view, pool,
                                             nextBlockScriptVerifyFlags, true,
                                             txdata, nSigChecksConsensus)) {
             // This can occur under some circumstances, if the node receives an
             // unrequested tx which is invalid due to new consensus rules not
             // being activated yet (during IBD).
             return error("%s: BUG! PLEASE REPORT THIS! CheckInputs failed "
                          "against next-block but not STANDARD flags %s, %s",
                          __func__, txid.ToString(), FormatStateMessage(state));
         }
 
+        if (nSigChecksStandard != nSigChecksConsensus) {
+            // We can't accept this transaction as we've used the standard count
+            // for the mempool/mining, but the consensus count will be enforced
+            // in validation (we don't want to produce bad block templates).
+            return error(
+                "%s: BUG! PLEASE REPORT THIS! SigChecks count differed between "
+                "standard and consensus flags in %s",
+                __func__, txid.ToString());
+        }
+
         if (test_accept) {
             // Tx was accepted, but not added
             return true;
         }
 
         // Store transaction in memory.
         pool.addUnchecked(entry, setAncestors);
 
         // Trim mempool and check if tx was trimmed.
         if (!bypass_limits) {
             pool.LimitSize(
                 gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000,
                 gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 *
                     60);
             if (!pool.exists(txid)) {
                 return state.DoS(0, false, REJECT_INSUFFICIENTFEE,
                                  "mempool full");
             }
         }
     }
 
     GetMainSignals().TransactionAddedToMempool(ptx);
     return true;
 }
 
 /**
  * (try to) add transaction to memory pool with a specified acceptance time.
  */
 static bool
 AcceptToMemoryPoolWithTime(const Config &config, CTxMemPool &pool,
                            CValidationState &state, const CTransactionRef &tx,
                            bool *pfMissingInputs, int64_t nAcceptTime,
                            bool bypass_limits, const Amount nAbsurdFee,
                            bool test_accept) EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
     AssertLockHeld(cs_main);
     std::vector<COutPoint> coins_to_uncache;
     bool res = AcceptToMemoryPoolWorker(
         config, pool, state, tx, pfMissingInputs, nAcceptTime, bypass_limits,
         nAbsurdFee, coins_to_uncache, test_accept);
     if (!res) {
         for (const COutPoint &outpoint : coins_to_uncache) {
             pcoinsTip->Uncache(outpoint);
         }
     }
 
     // After we've (potentially) uncached entries, ensure our coins cache is
     // still within its size limits
     CValidationState stateDummy;
     FlushStateToDisk(config.GetChainParams(), stateDummy,
                      FlushStateMode::PERIODIC);
     return res;
 }
 
 bool AcceptToMemoryPool(const Config &config, CTxMemPool &pool,
                         CValidationState &state, const CTransactionRef &tx,
                         bool *pfMissingInputs, bool bypass_limits,
                         const Amount nAbsurdFee, bool test_accept) {
     return AcceptToMemoryPoolWithTime(config, pool, state, tx, pfMissingInputs,
                                       GetTime(), bypass_limits, nAbsurdFee,
                                       test_accept);
 }
 
 /**
  * Return transaction in txOut, and if it was found inside a block, its hash is
  * placed in hashBlock. If blockIndex is provided, the transaction is fetched
  * from the corresponding block.
  */
 bool GetTransaction(const TxId &txid, CTransactionRef &txOut,
                     const Consensus::Params &params, BlockHash &hashBlock,
                     bool fAllowSlow, const CBlockIndex *const blockIndex) {
     CBlockIndex const *pindexSlow = blockIndex;
 
     LOCK(cs_main);
 
     if (!blockIndex) {
         CTransactionRef ptx = g_mempool.get(txid);
         if (ptx) {
             txOut = ptx;
             return true;
         }
 
         if (g_txindex) {
             return g_txindex->FindTx(txid, hashBlock, txOut);
         }
 
         // use coin database to locate block that contains transaction, and scan
         // it
         if (fAllowSlow) {
             const Coin &coin = AccessByTxid(*pcoinsTip, txid);
             if (!coin.IsSpent()) {
                 pindexSlow = chainActive[coin.GetHeight()];
             }
         }
     }
 
     if (pindexSlow) {
         CBlock block;
         if (ReadBlockFromDisk(block, pindexSlow, params)) {
             for (const auto &tx : block.vtx) {
                 if (tx->GetId() == txid) {
                     txOut = tx;
                     hashBlock = pindexSlow->GetBlockHash();
                     return true;
                 }
             }
         }
     }
 
     return false;
 }
 
 //////////////////////////////////////////////////////////////////////////////
 //
 // CBlock and CBlockIndex
 //
 
 static bool WriteBlockToDisk(const CBlock &block, FlatFilePos &pos,
                              const CMessageHeader::MessageMagic &messageStart) {
     // Open history file to append
     CAutoFile fileout(OpenBlockFile(pos), SER_DISK, CLIENT_VERSION);
     if (fileout.IsNull()) {
         return error("WriteBlockToDisk: OpenBlockFile failed");
     }
 
     // Write index header
     unsigned int nSize = GetSerializeSize(block, fileout.GetVersion());
     fileout << messageStart << nSize;
 
     // Write block
     long fileOutPos = ftell(fileout.Get());
     if (fileOutPos < 0) {
         return error("WriteBlockToDisk: ftell failed");
     }
 
     pos.nPos = (unsigned int)fileOutPos;
     fileout << block;
 
     return true;
 }
 
 bool ReadBlockFromDisk(CBlock &block, const FlatFilePos &pos,
                        const Consensus::Params &params) {
     block.SetNull();
 
     // Open history file to read
     CAutoFile filein(OpenBlockFile(pos, true), SER_DISK, CLIENT_VERSION);
     if (filein.IsNull()) {
         return error("ReadBlockFromDisk: OpenBlockFile failed for %s",
                      pos.ToString());
     }
 
     // Read block
     try {
         filein >> block;
     } catch (const std::exception &e) {
         return error("%s: Deserialize or I/O error - %s at %s", __func__,
                      e.what(), pos.ToString());
     }
 
     // Check the header
     if (!CheckProofOfWork(block.GetHash(), block.nBits, params)) {
         return error("ReadBlockFromDisk: Errors in block header at %s",
                      pos.ToString());
     }
 
     return true;
 }
 
 bool ReadBlockFromDisk(CBlock &block, const CBlockIndex *pindex,
                        const Consensus::Params &params) {
     FlatFilePos blockPos;
     {
         LOCK(cs_main);
         blockPos = pindex->GetBlockPos();
     }
 
     if (!ReadBlockFromDisk(block, blockPos, params)) {
         return false;
     }
 
     if (block.GetHash() != pindex->GetBlockHash()) {
         return error("ReadBlockFromDisk(CBlock&, CBlockIndex*): GetHash() "
                      "doesn't match index for %s at %s",
                      pindex->ToString(), pindex->GetBlockPos().ToString());
     }
 
     return true;
 }
 
 Amount GetBlockSubsidy(int nHeight, const Consensus::Params &consensusParams) {
     int halvings = nHeight / consensusParams.nSubsidyHalvingInterval;
     // Force block reward to zero when right shift is undefined.
     if (halvings >= 64) {
         return Amount::zero();
     }
 
     Amount nSubsidy = 50 * COIN;
     // Subsidy is cut in half every 210,000 blocks which will occur
     // approximately every 4 years.
     return ((nSubsidy / SATOSHI) >> halvings) * SATOSHI;
 }
 
 bool IsInitialBlockDownload() {
     // Once this function has returned false, it must remain false.
     static std::atomic<bool> latchToFalse{false};
     // Optimization: pre-test latch before taking the lock.
     if (latchToFalse.load(std::memory_order_relaxed)) {
         return false;
     }
 
     LOCK(cs_main);
     if (latchToFalse.load(std::memory_order_relaxed)) {
         return false;
     }
     if (fImporting || fReindex) {
         return true;
     }
     if (chainActive.Tip() == nullptr) {
         return true;
     }
     if (chainActive.Tip()->nChainWork < nMinimumChainWork) {
         return true;
     }
     if (chainActive.Tip()->GetBlockTime() < (GetTime() - nMaxTipAge)) {
         return true;
     }
     LogPrintf("Leaving InitialBlockDownload (latching to false)\n");
     latchToFalse.store(true, std::memory_order_relaxed);
     return false;
 }
 
 CBlockIndex const *pindexBestForkTip = nullptr;
 CBlockIndex const *pindexBestForkBase = nullptr;
 
 static void AlertNotify(const std::string &strMessage) {
     uiInterface.NotifyAlertChanged();
     std::string strCmd = gArgs.GetArg("-alertnotify", "");
     if (strCmd.empty()) {
         return;
     }
 
     // Alert text should be plain ascii coming from a trusted source, but to be
     // safe we first strip anything not in safeChars, then add single quotes
     // around the whole string before passing it to the shell:
     std::string singleQuote("'");
     std::string safeStatus = SanitizeString(strMessage);
     safeStatus = singleQuote + safeStatus + singleQuote;
     boost::replace_all(strCmd, "%s", safeStatus);
 
     std::thread t(runCommand, strCmd);
     // thread runs free
     t.detach();
 }
 
 static void CheckForkWarningConditions() EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
     AssertLockHeld(cs_main);
     // Before we get past initial download, we cannot reliably alert about forks
     // (we assume we don't get stuck on a fork before finishing our initial
     // sync)
     if (IsInitialBlockDownload()) {
         return;
     }
 
     // If our best fork is no longer within 72 blocks (+/- 12 hours if no one
     // mines it) of our head, drop it
     if (pindexBestForkTip &&
         chainActive.Height() - pindexBestForkTip->nHeight >= 72) {
         pindexBestForkTip = nullptr;
     }
 
     if (pindexBestForkTip ||
         (pindexBestInvalid &&
          pindexBestInvalid->nChainWork >
              chainActive.Tip()->nChainWork +
                  (GetBlockProof(*chainActive.Tip()) * 6))) {
         if (!GetfLargeWorkForkFound() && pindexBestForkBase) {
             std::string warning =
                 std::string("'Warning: Large-work fork detected, forking after "
                             "block ") +
                 pindexBestForkBase->phashBlock->ToString() + std::string("'");
             AlertNotify(warning);
         }
 
         if (pindexBestForkTip && pindexBestForkBase) {
             LogPrintf("%s: Warning: Large fork found\n  forking the "
                       "chain at height %d (%s)\n  lasting to height %d "
                       "(%s).\nChain state database corruption likely.\n",
                       __func__, pindexBestForkBase->nHeight,
                       pindexBestForkBase->phashBlock->ToString(),
                       pindexBestForkTip->nHeight,
                       pindexBestForkTip->phashBlock->ToString());
             SetfLargeWorkForkFound(true);
         } else {
             LogPrintf("%s: Warning: Found invalid chain at least ~6 blocks "
                       "longer than our best chain.\nChain state database "
                       "corruption likely.\n",
                       __func__);
             SetfLargeWorkInvalidChainFound(true);
         }
     } else {
         SetfLargeWorkForkFound(false);
         SetfLargeWorkInvalidChainFound(false);
     }
 }
 
 static void CheckForkWarningConditionsOnNewFork(CBlockIndex *pindexNewForkTip)
     EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
     AssertLockHeld(cs_main);
     // If we are on a fork that is sufficiently large, set a warning flag.
     const CBlockIndex *pfork = chainActive.FindFork(pindexNewForkTip);
 
     // We define a condition where we should warn the user about as a fork of at
     // least 7 blocks with a tip within 72 blocks (+/- 12 hours if no one mines
     // it) of ours. We use 7 blocks rather arbitrarily as it represents just
     // under 10% of sustained network hash rate operating on the fork, or a
     // chain that is entirely longer than ours and invalid (note that this
     // should be detected by both). We define it this way because it allows us
     // to only store the highest fork tip (+ base) which meets the 7-block
     // condition and from this always have the most-likely-to-cause-warning fork
     if (pfork &&
         (!pindexBestForkTip ||
          pindexNewForkTip->nHeight > pindexBestForkTip->nHeight) &&
         pindexNewForkTip->nChainWork - pfork->nChainWork >
             (GetBlockProof(*pfork) * 7) &&
         chainActive.Height() - pindexNewForkTip->nHeight < 72) {
         pindexBestForkTip = pindexNewForkTip;
         pindexBestForkBase = pfork;
     }
 
     CheckForkWarningConditions();
 }
 
 static void InvalidChainFound(CBlockIndex *pindexNew)
     EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
     AssertLockHeld(cs_main);
     if (!pindexBestInvalid ||
         pindexNew->nChainWork > pindexBestInvalid->nChainWork) {
         pindexBestInvalid = pindexNew;
     }
 
     // If the invalid chain found is supposed to be finalized, we need to move
     // back the finalization point.
     if (IsBlockFinalized(pindexNew)) {
         pindexFinalized = pindexNew->pprev;
     }
 
     LogPrintf("%s: invalid block=%s  height=%d  log2_work=%.8g  date=%s\n",
               __func__, pindexNew->GetBlockHash().ToString(),
               pindexNew->nHeight,
               log(pindexNew->nChainWork.getdouble()) / log(2.0),
               FormatISO8601DateTime(pindexNew->GetBlockTime()));
     CBlockIndex *tip = chainActive.Tip();
     assert(tip);
     LogPrintf("%s:  current best=%s  height=%d  log2_work=%.8g  date=%s\n",
               __func__, tip->GetBlockHash().ToString(), chainActive.Height(),
               log(tip->nChainWork.getdouble()) / log(2.0),
               FormatISO8601DateTime(tip->GetBlockTime()));
 }
 
 void CChainState::InvalidBlockFound(CBlockIndex *pindex,
                                     const CValidationState &state) {
     if (!state.CorruptionPossible()) {
         pindex->nStatus = pindex->nStatus.withFailed();
         m_failed_blocks.insert(pindex);
         setDirtyBlockIndex.insert(pindex);
         InvalidChainFound(pindex);
     }
 }
 
 void SpendCoins(CCoinsViewCache &view, const CTransaction &tx, CTxUndo &txundo,
                 int nHeight) {
     // Mark inputs spent.
     if (tx.IsCoinBase()) {
         return;
     }
 
     txundo.vprevout.reserve(tx.vin.size());
     for (const CTxIn &txin : tx.vin) {
         txundo.vprevout.emplace_back();
         bool is_spent = view.SpendCoin(txin.prevout, &txundo.vprevout.back());
         assert(is_spent);
     }
 }
 
 void UpdateCoins(CCoinsViewCache &view, const CTransaction &tx, CTxUndo &txundo,
                  int nHeight) {
     SpendCoins(view, tx, txundo, nHeight);
     AddCoins(view, tx, nHeight);
 }
 
 void UpdateCoins(CCoinsViewCache &view, const CTransaction &tx, int nHeight) {
     // Mark inputs spent.
     if (!tx.IsCoinBase()) {
         for (const CTxIn &txin : tx.vin) {
             bool is_spent = view.SpendCoin(txin.prevout);
             assert(is_spent);
         }
     }
 
     // Add outputs.
     AddCoins(view, tx, nHeight);
 }
 
 bool CScriptCheck::operator()() {
     const CScript &scriptSig = ptxTo->vin[nIn].scriptSig;
     if (!VerifyScript(scriptSig, scriptPubKey, nFlags,
                       CachingTransactionSignatureChecker(ptxTo, nIn, amount,
                                                          cacheStore, txdata),
                       metrics, &error)) {
         return false;
     }
     if (pLimitSigChecks &&
         !pLimitSigChecks->consume_and_check(metrics.nSigChecks)) {
         // we can't assign a meaningful script error (since the script
         // succeeded), but remove the ScriptError::OK which could be
         // misinterpreted.
         error = ScriptError::SIGCHECKS_LIMIT_EXCEEDED;
         return false;
     }
     return true;
 }
 
 int GetSpendHeight(const CCoinsViewCache &inputs) {
     LOCK(cs_main);
     CBlockIndex *pindexPrev = LookupBlockIndex(inputs.GetBestBlock());
     return pindexPrev->nHeight + 1;
 }
 
 bool CheckInputs(const CTransaction &tx, CValidationState &state,
                  const CCoinsViewCache &inputs, bool fScriptChecks,
                  const uint32_t flags, bool sigCacheStore,
                  bool scriptCacheStore,
                  const PrecomputedTransactionData &txdata, int &nSigChecksOut,
                  std::vector<CScriptCheck> *pvChecks /*= nullptr*/,
                  CheckInputsLimiter *pLimitSigChecks /*= nullptr*/) {
     AssertLockHeld(cs_main);
     assert(!tx.IsCoinBase());
 
     if (pvChecks) {
         pvChecks->reserve(tx.vin.size());
     }
 
     // Skip script verification when connecting blocks under the assumevalid
     // block. Assuming the assumevalid block is valid this is safe because
     // block merkle hashes are still computed and checked, of course, if an
     // assumed valid block is invalid due to false scriptSigs this optimization
     // would allow an invalid chain to be accepted.
     if (!fScriptChecks) {
         return true;
     }
 
     // First check if script executions have been cached with the same flags.
     // Note that this assumes that the inputs provided are correct (ie that the
     // transaction hash which is in tx's prevouts properly commits to the
     // scriptPubKey in the inputs view of that transaction).
     ScriptCacheKey hashCacheEntry(tx, flags);
     if (IsKeyInScriptCache(hashCacheEntry, !scriptCacheStore, nSigChecksOut)) {
         if (pLimitSigChecks &&
             !pLimitSigChecks->consume_and_check(nSigChecksOut)) {
             return state.Invalid(false, REJECT_NONSTANDARD,
                                  strprintf("too-many-sigchecks"));
         }
         return true;
     }
 
     int nSigChecksTotal = 0;
 
     for (size_t i = 0; i < tx.vin.size(); i++) {
         const COutPoint &prevout = tx.vin[i].prevout;
         const Coin &coin = inputs.AccessCoin(prevout);
         assert(!coin.IsSpent());
 
         // We very carefully only pass in things to CScriptCheck which are
         // clearly committed to by tx's hash. This provides a sanity
         // check that our caching is not introducing consensus failures through
         // additional data in, eg, the coins being spent being checked as a part
         // of CScriptCheck.
         const CScript &scriptPubKey = coin.GetTxOut().scriptPubKey;
         const Amount amount = coin.GetTxOut().nValue;
 
         // Verify signature
         CScriptCheck check(scriptPubKey, amount, tx, i, flags, sigCacheStore,
                            txdata, pLimitSigChecks);
         if (pvChecks) {
             pvChecks->push_back(std::move(check));
         } else if (!check()) {
             if (pLimitSigChecks && !pLimitSigChecks->check()) {
                 // It's not a script error to overrun the limit, and we just
                 // reject it as nonstandard.
                 return state.Invalid(false, REJECT_NONSTANDARD,
                                      strprintf("too-many-sigchecks"));
             }
 
             ScriptError scriptError = check.GetScriptError();
             // Compute flags without the optional standardness flags.
             // This differs from MANDATORY_SCRIPT_VERIFY_FLAGS as it contains
             // additional upgrade flags (see AcceptToMemoryPoolWorker variable
             // extraFlags).
             uint32_t mandatoryFlags =
                 flags & ~STANDARD_NOT_MANDATORY_VERIFY_FLAGS;
             if (flags != mandatoryFlags) {
                 // Check whether the failure was caused by a non-mandatory
                 // script verification check. If so, don't trigger DoS
                 // protection to avoid splitting the network on the basis of
                 // relay policy disagreements.
                 CScriptCheck check2(scriptPubKey, amount, tx, i, mandatoryFlags,
                                     sigCacheStore, txdata);
                 if (check2()) {
                     return state.Invalid(
                         false, REJECT_NONSTANDARD,
                         strprintf("non-mandatory-script-verify-flag (%s)",
                                   ScriptErrorString(scriptError)));
                 }
                 // update the error message to reflect the mandatory violation.
                 scriptError = check2.GetScriptError();
             }
 
             // Before banning, we need to check whether the transaction would
             // be valid on the other side of the upgrade, so as to avoid
             // splitting the network between upgraded and non-upgraded nodes.
             // Note that this will create strange error messages like
             // "upgrade-conditional-script-failure (Opcode missing or not
             // understood)".
             CScriptCheck check3(scriptPubKey, amount, tx, i,
                                 mandatoryFlags ^ SCRIPT_ENABLE_OP_REVERSEBYTES,
                                 sigCacheStore, txdata);
             if (check3()) {
                 return state.Invalid(
                     false, REJECT_INVALID,
                     strprintf("upgrade-conditional-script-failure (%s)",
                               ScriptErrorString(check.GetScriptError())));
             }
 
             // Failures of other flags indicate a transaction that is invalid in
             // new blocks, e.g. a invalid P2SH. We DoS ban such nodes as they
             // are not following the protocol. That said during an upgrade
             // careful thought should be taken as to the correct behavior - we
             // may want to continue peering with non-upgraded nodes even after
             // soft-fork super-majority signaling has occurred.
             return state.DoS(
                 100, false, REJECT_INVALID,
                 strprintf("mandatory-script-verify-flag-failed (%s)",
                           ScriptErrorString(scriptError)));
         }
 
         nSigChecksTotal += check.GetScriptExecutionMetrics().nSigChecks;
     }
 
     nSigChecksOut = nSigChecksTotal;
 
     if (scriptCacheStore && !pvChecks) {
         // We executed all of the provided scripts, and were told to cache the
         // result. Do so now.
         AddKeyInScriptCache(hashCacheEntry, nSigChecksTotal);
     }
 
     return true;
 }
 
 namespace {
 
 bool UndoWriteToDisk(const CBlockUndo &blockundo, FlatFilePos &pos,
                      const uint256 &hashBlock,
                      const CMessageHeader::MessageMagic &messageStart) {
     // Open history file to append
     CAutoFile fileout(OpenUndoFile(pos), SER_DISK, CLIENT_VERSION);
     if (fileout.IsNull()) {
         return error("%s: OpenUndoFile failed", __func__);
     }
 
     // Write index header
     unsigned int nSize = GetSerializeSize(blockundo, fileout.GetVersion());
     fileout << messageStart << nSize;
 
     // Write undo data
     long fileOutPos = ftell(fileout.Get());
     if (fileOutPos < 0) {
         return error("%s: ftell failed", __func__);
     }
     pos.nPos = (unsigned int)fileOutPos;
     fileout << blockundo;
 
     // calculate & write checksum
     CHashWriter hasher(SER_GETHASH, PROTOCOL_VERSION);
     hasher << hashBlock;
     hasher << blockundo;
     fileout << hasher.GetHash();
 
     return true;
 }
 
 static bool UndoReadFromDisk(CBlockUndo &blockundo, const CBlockIndex *pindex) {
     FlatFilePos pos = pindex->GetUndoPos();
     if (pos.IsNull()) {
         return error("%s: no undo data available", __func__);
     }
 
     // Open history file to read
     CAutoFile filein(OpenUndoFile(pos, true), SER_DISK, CLIENT_VERSION);
     if (filein.IsNull()) {
         return error("%s: OpenUndoFile failed", __func__);
     }
 
     // Read block
     uint256 hashChecksum;
     // We need a CHashVerifier as reserializing may lose data
     CHashVerifier<CAutoFile> verifier(&filein);
     try {
         verifier << pindex->pprev->GetBlockHash();
         verifier >> blockundo;
         filein >> hashChecksum;
     } catch (const std::exception &e) {
         return error("%s: Deserialize or I/O error - %s", __func__, e.what());
     }
 
     // Verify checksum
     if (hashChecksum != verifier.GetHash()) {
         return error("%s: Checksum mismatch", __func__);
     }
 
     return true;
 }
 
 /** Abort with a message */
 static bool AbortNode(const std::string &strMessage,
                       const std::string &userMessage = "") {
     SetMiscWarning(strMessage);
     LogPrintf("*** %s\n", strMessage);
     uiInterface.ThreadSafeMessageBox(
         userMessage.empty() ? _("Error: A fatal internal error occurred, see "
                                 "debug.log for details")
                             : userMessage,
         "", CClientUIInterface::MSG_ERROR);
     StartShutdown();
     return false;
 }
 
 static bool AbortNode(CValidationState &state, const std::string &strMessage,
                       const std::string &userMessage = "") {
     AbortNode(strMessage, userMessage);
     return state.Error(strMessage);
 }
 
 } // namespace
 
 /** Restore the UTXO in a Coin at a given COutPoint. */
 DisconnectResult UndoCoinSpend(const Coin &undo, CCoinsViewCache &view,
                                const COutPoint &out) {
     bool fClean = true;
 
     if (view.HaveCoin(out)) {
         // Overwriting transaction output.
         fClean = false;
     }
 
     if (undo.GetHeight() == 0) {
         // Missing undo metadata (height and coinbase). Older versions included
         // this information only in undo records for the last spend of a
         // transactions' outputs. This implies that it must be present for some
         // other output of the same tx.
         const Coin &alternate = AccessByTxid(view, out.GetTxId());
         if (alternate.IsSpent()) {
             // Adding output for transaction without known metadata
             return DISCONNECT_FAILED;
         }
 
         // This is somewhat ugly, but hopefully utility is limited. This is only
         // useful when working from legacy on disck data. In any case, putting
         // the correct information in there doesn't hurt.
         const_cast<Coin &>(undo) = Coin(undo.GetTxOut(), alternate.GetHeight(),
                                         alternate.IsCoinBase());
     }
 
     // The potential_overwrite parameter to AddCoin is only allowed to be false
     // if we know for sure that the coin did not already exist in the cache. As
     // we have queried for that above using HaveCoin, we don't need to guess.
     // When fClean is false, a coin already existed and it is an overwrite.
     view.AddCoin(out, std::move(undo), !fClean);
 
     return fClean ? DISCONNECT_OK : DISCONNECT_UNCLEAN;
 }
 
 /**
  * Undo the effects of this block (with given index) on the UTXO set represented
  * by coins. When FAILED is returned, view is left in an indeterminate state.
  */
 DisconnectResult CChainState::DisconnectBlock(const CBlock &block,
                                               const CBlockIndex *pindex,
                                               CCoinsViewCache &view) {
     CBlockUndo blockUndo;
     if (!UndoReadFromDisk(blockUndo, pindex)) {
         error("DisconnectBlock(): failure reading undo data");
         return DISCONNECT_FAILED;
     }
 
     return ApplyBlockUndo(blockUndo, block, pindex, view);
 }
 
 DisconnectResult ApplyBlockUndo(const CBlockUndo &blockUndo,
                                 const CBlock &block, const CBlockIndex *pindex,
                                 CCoinsViewCache &view) {
     bool fClean = true;
 
     if (blockUndo.vtxundo.size() + 1 != block.vtx.size()) {
         error("DisconnectBlock(): block and undo data inconsistent");
         return DISCONNECT_FAILED;
     }
 
     // First, restore inputs.
     for (size_t i = 1; i < block.vtx.size(); i++) {
         const CTransaction &tx = *(block.vtx[i]);
         const CTxUndo &txundo = blockUndo.vtxundo[i - 1];
         if (txundo.vprevout.size() != tx.vin.size()) {
             error("DisconnectBlock(): transaction and undo data inconsistent");
             return DISCONNECT_FAILED;
         }
 
         for (size_t j = 0; j < tx.vin.size(); j++) {
             const COutPoint &out = tx.vin[j].prevout;
             const Coin &undo = txundo.vprevout[j];
             DisconnectResult res = UndoCoinSpend(undo, view, out);
             if (res == DISCONNECT_FAILED) {
                 return DISCONNECT_FAILED;
             }
             fClean = fClean && res != DISCONNECT_UNCLEAN;
         }
     }
 
     // Second, revert created outputs.
     for (const auto &ptx : block.vtx) {
         const CTransaction &tx = *ptx;
         const TxId &txid = tx.GetId();
         const bool is_coinbase = tx.IsCoinBase();
 
         // Check that all outputs are available and match the outputs in the
         // block itself exactly.
         for (size_t o = 0; o < tx.vout.size(); o++) {
             if (tx.vout[o].scriptPubKey.IsUnspendable()) {
                 continue;
             }
 
             COutPoint out(txid, o);
             Coin coin;
             bool is_spent = view.SpendCoin(out, &coin);
             if (!is_spent || tx.vout[o] != coin.GetTxOut() ||
                 uint32_t(pindex->nHeight) != coin.GetHeight() ||
                 is_coinbase != coin.IsCoinBase()) {
                 // transaction output mismatch
                 fClean = false;
             }
         }
     }
 
     // Move best block pointer to previous block.
     view.SetBestBlock(block.hashPrevBlock);
 
     return fClean ? DISCONNECT_OK : DISCONNECT_UNCLEAN;
 }
 
 static void FlushBlockFile(bool fFinalize = false) {
     LOCK(cs_LastBlockFile);
 
     FlatFilePos block_pos_old(nLastBlockFile,
                               vinfoBlockFile[nLastBlockFile].nSize);
     FlatFilePos undo_pos_old(nLastBlockFile,
                              vinfoBlockFile[nLastBlockFile].nUndoSize);
 
     bool status = true;
     status &= BlockFileSeq().Flush(block_pos_old, fFinalize);
     status &= UndoFileSeq().Flush(undo_pos_old, fFinalize);
     if (!status) {
         AbortNode("Flushing block file to disk failed. This is likely the "
                   "result of an I/O error.");
     }
 }
 
 static bool FindUndoPos(CValidationState &state, int nFile, FlatFilePos &pos,
                         unsigned int nAddSize);
 
 static bool WriteUndoDataForBlock(const CBlockUndo &blockundo,
                                   CValidationState &state, CBlockIndex *pindex,
                                   const CChainParams &chainparams) {
     // Write undo information to disk
     if (pindex->GetUndoPos().IsNull()) {
         FlatFilePos _pos;
         if (!FindUndoPos(state, pindex->nFile, _pos,
                          ::GetSerializeSize(blockundo, CLIENT_VERSION) + 40)) {
             return error("ConnectBlock(): FindUndoPos failed");
         }
         if (!UndoWriteToDisk(blockundo, _pos, pindex->pprev->GetBlockHash(),
                              chainparams.DiskMagic())) {
             return AbortNode(state, "Failed to write undo data");
         }
 
         // update nUndoPos in block index
         pindex->nUndoPos = _pos.nPos;
         pindex->nStatus = pindex->nStatus.withUndo();
         setDirtyBlockIndex.insert(pindex);
     }
 
     return true;
 }
 
 static CCheckQueue<CScriptCheck> scriptcheckqueue(128);
 
 void ThreadScriptCheck() {
     RenameThread("bitcoin-scriptch");
     scriptcheckqueue.Thread();
 }
 
 VersionBitsCache versionbitscache GUARDED_BY(cs_main);
 
 int32_t ComputeBlockVersion(const CBlockIndex *pindexPrev,
                             const Consensus::Params &params) {
     LOCK(cs_main);
     int32_t nVersion = VERSIONBITS_TOP_BITS;
 
     for (int i = 0; i < (int)Consensus::MAX_VERSION_BITS_DEPLOYMENTS; i++) {
         ThresholdState state = VersionBitsState(
             pindexPrev, params, static_cast<Consensus::DeploymentPos>(i),
             versionbitscache);
         if (state == ThresholdState::LOCKED_IN ||
             state == ThresholdState::STARTED) {
             nVersion |= VersionBitsMask(
                 params, static_cast<Consensus::DeploymentPos>(i));
         }
     }
 
     return nVersion;
 }
 
 // Returns the script flags which should be checked for the block after
 // the given block.
 static uint32_t GetNextBlockScriptFlags(const Consensus::Params &params,
                                         const CBlockIndex *pindex) {
     uint32_t flags = SCRIPT_VERIFY_NONE;
 
     // Start enforcing P2SH (BIP16)
     if ((pindex->nHeight + 1) >= params.BIP16Height) {
         flags |= SCRIPT_VERIFY_P2SH;
     }
 
     // Start enforcing the DERSIG (BIP66) rule.
     if ((pindex->nHeight + 1) >= params.BIP66Height) {
         flags |= SCRIPT_VERIFY_DERSIG;
     }
 
     // Start enforcing CHECKLOCKTIMEVERIFY (BIP65) rule.
     if ((pindex->nHeight + 1) >= params.BIP65Height) {
         flags |= SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY;
     }
 
     // Start enforcing CSV (BIP68, BIP112 and BIP113) rule.
     if ((pindex->nHeight + 1) >= params.CSVHeight) {
         flags |= SCRIPT_VERIFY_CHECKSEQUENCEVERIFY;
     }
 
     // If the UAHF is enabled, we start accepting replay protected txns
     if (IsUAHFenabled(params, pindex)) {
         flags |= SCRIPT_VERIFY_STRICTENC;
         flags |= SCRIPT_ENABLE_SIGHASH_FORKID;
     }
 
     // If the DAA HF is enabled, we start rejecting transaction that use a high
     // s in their signature. We also make sure that signature that are supposed
     // to fail (for instance in multisig or other forms of smart contracts) are
     // null.
     if (IsDAAEnabled(params, pindex)) {
         flags |= SCRIPT_VERIFY_LOW_S;
         flags |= SCRIPT_VERIFY_NULLFAIL;
     }
 
     // When the magnetic anomaly fork is enabled, we start accepting
     // transactions using the OP_CHECKDATASIG opcode and it's verify
     // alternative. We also start enforcing push only signatures and
     // clean stack.
     if (IsMagneticAnomalyEnabled(params, pindex)) {
         flags |= SCRIPT_VERIFY_CHECKDATASIG_SIGOPS;
         flags |= SCRIPT_VERIFY_SIGPUSHONLY;
         flags |= SCRIPT_VERIFY_CLEANSTACK;
     }
 
     if (IsGravitonEnabled(params, pindex)) {
         flags |= SCRIPT_ENABLE_SCHNORR_MULTISIG;
         flags |= SCRIPT_VERIFY_MINIMALDATA;
     }
 
     if (IsPhononEnabled(params, pindex)) {
         flags |= SCRIPT_ENABLE_OP_REVERSEBYTES;
+        flags |= SCRIPT_REPORT_SIGCHECKS;
         flags |= SCRIPT_ZERO_SIGOPS;
     }
 
     // We make sure this node will have replay protection during the next hard
     // fork.
     if (IsReplayProtectionEnabled(params, pindex)) {
         flags |= SCRIPT_ENABLE_REPLAY_PROTECTION;
     }
 
     return flags;
 }
 
 static int64_t nTimeCheck = 0;
 static int64_t nTimeForks = 0;
 static int64_t nTimeVerify = 0;
 static int64_t nTimeConnect = 0;
 static int64_t nTimeIndex = 0;
 static int64_t nTimeCallbacks = 0;
 static int64_t nTimeTotal = 0;
 static int64_t nBlocksTotal = 0;
 
 /**
  * Apply the effects of this block (with given index) on the UTXO set
  * represented by coins. Validity checks that depend on the UTXO set are also
  * done; ConnectBlock() can fail if those validity checks fail (among other
  * reasons).
  */
 bool CChainState::ConnectBlock(const CBlock &block, CValidationState &state,
                                CBlockIndex *pindex, CCoinsViewCache &view,
                                const CChainParams &params,
                                BlockValidationOptions options,
                                bool fJustCheck) {
     AssertLockHeld(cs_main);
     assert(pindex);
     assert(*pindex->phashBlock == block.GetHash());
     int64_t nTimeStart = GetTimeMicros();
 
     const Consensus::Params &consensusParams = params.GetConsensus();
 
     // Check it again in case a previous version let a bad block in
     // NOTE: We don't currently (re-)invoke ContextualCheckBlock() or
     // ContextualCheckBlockHeader() here. This means that if we add a new
     // consensus rule that is enforced in one of those two functions, then we
     // may have let in a block that violates the rule prior to updating the
     // software, and we would NOT be enforcing the rule here. Fully solving
     // upgrade from one software version to the next after a consensus rule
     // change is potentially tricky and issue-specific.
     // Also, currently the rule against blocks more than 2 hours in the future
     // is enforced in ContextualCheckBlockHeader(); we wouldn't want to
     // re-enforce that rule here (at least until we make it impossible for
     // GetAdjustedTime() to go backward).
     if (!CheckBlock(block, state, consensusParams,
                     options.withCheckPoW(!fJustCheck)
                         .withCheckMerkleRoot(!fJustCheck))) {
         if (state.CorruptionPossible()) {
             // We don't write down blocks to disk if they may have been
             // corrupted, so this should be impossible unless we're having
             // hardware problems.
             return AbortNode(state, "Corrupt block found indicating potential "
                                     "hardware failure; shutting down");
         }
         return error("%s: Consensus::CheckBlock: %s", __func__,
                      FormatStateMessage(state));
     }
 
     // Verify that the view's current state corresponds to the previous block
     BlockHash hashPrevBlock =
         pindex->pprev == nullptr ? BlockHash() : pindex->pprev->GetBlockHash();
     assert(hashPrevBlock == view.GetBestBlock());
 
     // Special case for the genesis block, skipping connection of its
     // transactions (its coinbase is unspendable)
     if (block.GetHash() == consensusParams.hashGenesisBlock) {
         if (!fJustCheck) {
             view.SetBestBlock(pindex->GetBlockHash());
         }
 
         return true;
     }
 
     nBlocksTotal++;
 
     bool fScriptChecks = true;
     if (!hashAssumeValid.IsNull()) {
         // We've been configured with the hash of a block which has been
         // externally verified to have a valid history. A suitable default value
         // is included with the software and updated from time to time. Because
         // validity relative to a piece of software is an objective fact these
         // defaults can be easily reviewed. This setting doesn't force the
         // selection of any particular chain but makes validating some faster by
         // effectively caching the result of part of the verification.
         BlockMap::const_iterator it = mapBlockIndex.find(hashAssumeValid);
         if (it != mapBlockIndex.end()) {
             if (it->second->GetAncestor(pindex->nHeight) == pindex &&
                 pindexBestHeader->GetAncestor(pindex->nHeight) == pindex &&
                 pindexBestHeader->nChainWork >= nMinimumChainWork) {
                 // This block is a member of the assumed verified chain and an
                 // ancestor of the best header. The equivalent time check
                 // discourages hash power from extorting the network via DOS
                 // attack into accepting an invalid block through telling users
                 // they must manually set assumevalid. Requiring a software
                 // change or burying the invalid block, regardless of the
                 // setting, makes it hard to hide the implication of the demand.
                 // This also avoids having release candidates that are hardly
                 // doing any signature verification at all in testing without
                 // having to artificially set the default assumed verified block
                 // further back. The test against nMinimumChainWork prevents the
                 // skipping when denied access to any chain at least as good as
                 // the expected chain.
                 fScriptChecks =
                     (GetBlockProofEquivalentTime(
                          *pindexBestHeader, *pindex, *pindexBestHeader,
                          consensusParams) <= 60 * 60 * 24 * 7 * 2);
             }
         }
     }
 
     int64_t nTime1 = GetTimeMicros();
     nTimeCheck += nTime1 - nTimeStart;
     LogPrint(BCLog::BENCH, "    - Sanity checks: %.2fms [%.2fs (%.2fms/blk)]\n",
              MILLI * (nTime1 - nTimeStart), nTimeCheck * MICRO,
              nTimeCheck * MILLI / nBlocksTotal);
 
     // Do not allow blocks that contain transactions which 'overwrite' older
     // transactions, unless those are already completely spent. If such
     // overwrites are allowed, coinbases and transactions depending upon those
     // can be duplicated to remove the ability to spend the first instance --
     // even after being sent to another address. See BIP30 and
     // http://r6.ca/blog/20120206T005236Z.html for more information. This logic
     // is not necessary for memory pool transactions, as AcceptToMemoryPool
     // already refuses previously-known transaction ids entirely. This rule was
     // originally applied to all blocks with a timestamp after March 15, 2012,
     // 0:00 UTC. Now that the whole chain is irreversibly beyond that time it is
     // applied to all blocks except the two in the chain that violate it. This
     // prevents exploiting the issue against nodes during their initial block
     // download.
     bool fEnforceBIP30 = !((pindex->nHeight == 91842 &&
                             pindex->GetBlockHash() ==
                                 uint256S("0x00000000000a4d0a398161ffc163c503763"
                                          "b1f4360639393e0e4c8e300e0caec")) ||
                            (pindex->nHeight == 91880 &&
                             pindex->GetBlockHash() ==
                                 uint256S("0x00000000000743f190a18c5577a3c2d2a1f"
                                          "610ae9601ac046a38084ccb7cd721")));
 
     // Once BIP34 activated it was not possible to create new duplicate
     // coinbases and thus other than starting with the 2 existing duplicate
     // coinbase pairs, not possible to create overwriting txs. But by the time
     // BIP34 activated, in each of the existing pairs the duplicate coinbase had
     // overwritten the first before the first had been spent. Since those
     // coinbases are sufficiently buried it's no longer possible to create
     // further duplicate transactions descending from the known pairs either. If
     // we're on the known chain at height greater than where BIP34 activated, we
     // can save the db accesses needed for the BIP30 check.
     assert(pindex->pprev);
     CBlockIndex *pindexBIP34height =
         pindex->pprev->GetAncestor(consensusParams.BIP34Height);
     // Only continue to enforce if we're below BIP34 activation height or the
     // block hash at that height doesn't correspond.
     fEnforceBIP30 =
         fEnforceBIP30 &&
         (!pindexBIP34height ||
          !(pindexBIP34height->GetBlockHash() == consensusParams.BIP34Hash));
 
     if (fEnforceBIP30) {
         for (const auto &tx : block.vtx) {
             for (size_t o = 0; o < tx->vout.size(); o++) {
                 if (view.HaveCoin(COutPoint(tx->GetId(), o))) {
                     return state.DoS(
                         100,
                         error("ConnectBlock(): tried to overwrite transaction"),
                         REJECT_INVALID, "bad-txns-BIP30");
                 }
             }
         }
     }
 
     // Start enforcing BIP68 (sequence locks).
     int nLockTimeFlags = 0;
     if (pindex->nHeight >= consensusParams.CSVHeight) {
         nLockTimeFlags |= LOCKTIME_VERIFY_SEQUENCE;
     }
 
     const uint32_t flags =
         GetNextBlockScriptFlags(consensusParams, pindex->pprev);
 
     int64_t nTime2 = GetTimeMicros();
     nTimeForks += nTime2 - nTime1;
     LogPrint(BCLog::BENCH, "    - Fork checks: %.2fms [%.2fs (%.2fms/blk)]\n",
              MILLI * (nTime2 - nTime1), nTimeForks * MICRO,
              nTimeForks * MILLI / nBlocksTotal);
 
     CBlockUndo blockundo;
 
     CCheckQueueControl<CScriptCheck> control(fScriptChecks ? &scriptcheckqueue
                                                            : nullptr);
 
     std::vector<int> prevheights;
     Amount nFees = Amount::zero();
     int nInputs = 0;
 
     // Sigops counting. We need to do it again because of P2SH.
     uint64_t nSigOpsCount = 0;
     const uint64_t currentBlockSize =
         ::GetSerializeSize(block, PROTOCOL_VERSION);
     const uint64_t nMaxSigOpsCount = GetMaxBlockSigOpsCount(currentBlockSize);
 
+    // Limit the total executed signature operations in the block, a consensus
+    // rule. Tracking during the CPU-consuming part (validation of uncached
+    // inputs) is per-input atomic and validation in each thread stops very
+    // quickly after the limit is exceeded, so an adversary cannot cause us to
+    // exceed the limit by much at all.
+    CheckInputsLimiter nSigChecksBlockLimiter(
+        GetMaxBlockSigChecksCount(options.getExcessiveBlockSize()));
+
     blockundo.vtxundo.reserve(block.vtx.size() - 1);
 
     // Add all outputs
     try {
         for (const auto &ptx : block.vtx) {
             AddCoins(view, *ptx, pindex->nHeight);
         }
     } catch (const std::logic_error &e) {
         // This error will be thrown from AddCoin if we try to connect a block
         // containing duplicate transactions. Such a thing should normally be
         // caught early nowadays (due to ContextualCheckBlock's CTOR
         // enforcement) however some edge cases can escape that:
         // - ContextualCheckBlock does not get re-run after saving the block to
         // disk, and older versions may have saved a weird block.
         // - its checks are not applied to pre-CTOR chains, which we might visit
         // with checkpointing off.
         return state.DoS(
             100, error("ConnectBlock(): tried to overwrite transaction"),
             REJECT_INVALID, "tx-duplicate");
     }
 
     for (const auto &ptx : block.vtx) {
         const CTransaction &tx = *ptx;
         const bool isCoinBase = tx.IsCoinBase();
         nInputs += tx.vin.size();
 
         Amount txfee = Amount::zero();
         if (!isCoinBase && !Consensus::CheckTxInputs(tx, state, view,
                                                      pindex->nHeight, txfee)) {
             return error("%s: Consensus::CheckTxInputs: %s, %s", __func__,
                          tx.GetId().ToString(), FormatStateMessage(state));
         }
         nFees += txfee;
         if (!MoneyRange(nFees)) {
             return state.DoS(
                 100,
                 error("%s: accumulated fee in the block out of range.",
                       __func__),
                 REJECT_INVALID, "bad-txns-accumulated-fee-outofrange");
         }
 
         // GetTransactionSigOpCount counts 2 types of sigops:
         // * legacy (always)
         // * p2sh (when P2SH enabled in flags and excludes coinbase)
         auto txSigOpsCount = GetTransactionSigOpCount(tx, view, flags);
         if (txSigOpsCount > MAX_TX_SIGOPS_COUNT) {
             return state.DoS(100, false, REJECT_INVALID, "bad-txn-sigops");
         }
 
         nSigOpsCount += txSigOpsCount;
         if (nSigOpsCount > nMaxSigOpsCount) {
             return state.DoS(100, error("ConnectBlock(): too many sigops"),
                              REJECT_INVALID, "bad-blk-sigops");
         }
 
         // The following checks do not apply to the coinbase.
         if (isCoinBase) {
             continue;
         }
 
         // Check that transaction is BIP68 final BIP68 lock checks (as
         // opposed to nLockTime checks) must be in ConnectBlock because they
         // require the UTXO set.
         prevheights.resize(tx.vin.size());
         for (size_t j = 0; j < tx.vin.size(); j++) {
             prevheights[j] = view.AccessCoin(tx.vin[j].prevout).GetHeight();
         }
 
         if (!SequenceLocks(tx, nLockTimeFlags, &prevheights, *pindex)) {
             return state.DoS(
                 100,
                 error("%s: contains a non-BIP68-final transaction", __func__),
                 REJECT_INVALID, "bad-txns-nonfinal");
         }
 
         // Don't cache results if we're actually connecting blocks (still
         // consult the cache, though).
         bool fCacheResults = fJustCheck;
 
         std::vector<CScriptCheck> vChecks;
         // nSigChecksRet may be accurate (found in cache) or 0 (checks were
         // deferred into vChecks).
         int nSigChecksRet;
         if (!CheckInputs(tx, state, view, fScriptChecks, flags, fCacheResults,
                          fCacheResults, PrecomputedTransactionData(tx),
-                         nSigChecksRet, &vChecks)) {
+                         nSigChecksRet, &vChecks, &nSigChecksBlockLimiter)) {
+            // Parallel CheckInputs shouldn't fail except for this reason, which
+            // is banworthy. Use "blk-bad-inputs" to mimic the parallel script
+            // check error.
+            if (!nSigChecksBlockLimiter.check()) {
+                return state.DoS(100, false, REJECT_INVALID, "blk-bad-inputs",
+                                 false, "CheckInputs exceeded SigChecks limit");
+            }
             return error("ConnectBlock(): CheckInputs on %s failed with %s",
                          tx.GetId().ToString(), FormatStateMessage(state));
         }
 
         control.Add(vChecks);
 
         blockundo.vtxundo.push_back(CTxUndo());
         // Note: this must execute in the same iteration as CheckTxInputs (not
         // in a separate loop) in order to detect double spends. However,
         // this does not prevent double-spending by duplicated transaction
         // inputs in the same transaction (cf. CVE-2018-17144) -- that check is
         // done in CheckBlock (CheckRegularTransaction).
         SpendCoins(view, tx, blockundo.vtxundo.back(), pindex->nHeight);
     }
 
     int64_t nTime3 = GetTimeMicros();
     nTimeConnect += nTime3 - nTime2;
     LogPrint(BCLog::BENCH,
              "      - Connect %u transactions: %.2fms (%.3fms/tx, %.3fms/txin) "
              "[%.2fs (%.2fms/blk)]\n",
              (unsigned)block.vtx.size(), MILLI * (nTime3 - nTime2),
              MILLI * (nTime3 - nTime2) / block.vtx.size(),
              nInputs <= 1 ? 0 : MILLI * (nTime3 - nTime2) / (nInputs - 1),
              nTimeConnect * MICRO, nTimeConnect * MILLI / nBlocksTotal);
 
     Amount blockReward =
         nFees + GetBlockSubsidy(pindex->nHeight, consensusParams);
     if (block.vtx[0]->GetValueOut() > blockReward) {
         return state.DoS(100,
                          error("ConnectBlock(): coinbase pays too much "
                                "(actual=%d vs limit=%d)",
                                block.vtx[0]->GetValueOut(), blockReward),
                          REJECT_INVALID, "bad-cb-amount");
     }
 
     if (!control.Wait()) {
         return state.DoS(100, false, REJECT_INVALID, "blk-bad-inputs", false,
                          "parallel script check failed");
     }
 
     int64_t nTime4 = GetTimeMicros();
     nTimeVerify += nTime4 - nTime2;
     LogPrint(
         BCLog::BENCH,
         "    - Verify %u txins: %.2fms (%.3fms/txin) [%.2fs (%.2fms/blk)]\n",
         nInputs - 1, MILLI * (nTime4 - nTime2),
         nInputs <= 1 ? 0 : MILLI * (nTime4 - nTime2) / (nInputs - 1),
         nTimeVerify * MICRO, nTimeVerify * MILLI / nBlocksTotal);
 
     if (fJustCheck) {
         return true;
     }
 
     if (!WriteUndoDataForBlock(blockundo, state, pindex, params)) {
         return false;
     }
 
     if (!pindex->IsValid(BlockValidity::SCRIPTS)) {
         pindex->RaiseValidity(BlockValidity::SCRIPTS);
         setDirtyBlockIndex.insert(pindex);
     }
 
     assert(pindex->phashBlock);
     // add this block to the view's block chain
     view.SetBestBlock(pindex->GetBlockHash());
 
     int64_t nTime5 = GetTimeMicros();
     nTimeIndex += nTime5 - nTime4;
     LogPrint(BCLog::BENCH, "    - Index writing: %.2fms [%.2fs (%.2fms/blk)]\n",
              MILLI * (nTime5 - nTime4), nTimeIndex * MICRO,
              nTimeIndex * MILLI / nBlocksTotal);
 
     int64_t nTime6 = GetTimeMicros();
     nTimeCallbacks += nTime6 - nTime5;
     LogPrint(BCLog::BENCH, "    - Callbacks: %.2fms [%.2fs (%.2fms/blk)]\n",
              MILLI * (nTime6 - nTime5), nTimeCallbacks * MICRO,
              nTimeCallbacks * MILLI / nBlocksTotal);
 
     return true;
 }
 
 /**
  * Update the on-disk chain state.
  * The caches and indexes are flushed depending on the mode we're called with if
  * they're too large, if it's been a while since the last write, or always and
  * in all cases if we're in prune mode and are deleting files.
  *
  * If FlushStateMode::NONE is used, then FlushStateToDisk(...) won't do anything
  * besides checking if we need to prune.
  */
 static bool FlushStateToDisk(const CChainParams &chainparams,
                              CValidationState &state, FlushStateMode mode,
                              int nManualPruneHeight) {
     int64_t nMempoolUsage = g_mempool.DynamicMemoryUsage();
     LOCK(cs_main);
     static int64_t nLastWrite = 0;
     static int64_t nLastFlush = 0;
     std::set<int> setFilesToPrune;
     bool full_flush_completed = false;
     try {
         {
             bool fFlushForPrune = false;
             bool fDoFullFlush = false;
             LOCK(cs_LastBlockFile);
             if (fPruneMode && (fCheckForPruning || nManualPruneHeight > 0) &&
                 !fReindex) {
                 if (nManualPruneHeight > 0) {
                     FindFilesToPruneManual(setFilesToPrune, nManualPruneHeight);
                 } else {
                     FindFilesToPrune(setFilesToPrune,
                                      chainparams.PruneAfterHeight());
                     fCheckForPruning = false;
                 }
                 if (!setFilesToPrune.empty()) {
                     fFlushForPrune = true;
                     if (!fHavePruned) {
                         pblocktree->WriteFlag("prunedblockfiles", true);
                         fHavePruned = true;
                     }
                 }
             }
             int64_t nNow = GetTimeMicros();
             // Avoid writing/flushing immediately after startup.
             if (nLastWrite == 0) {
                 nLastWrite = nNow;
             }
             if (nLastFlush == 0) {
                 nLastFlush = nNow;
             }
             int64_t nMempoolSizeMax =
                 gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
             int64_t cacheSize = pcoinsTip->DynamicMemoryUsage();
             int64_t nTotalSpace =
                 nCoinCacheUsage +
                 std::max<int64_t>(nMempoolSizeMax - nMempoolUsage, 0);
             // The cache is large and we're within 10% and 10 MiB of the limit,
             // but we have time now (not in the middle of a block processing).
             bool fCacheLarge =
                 mode == FlushStateMode::PERIODIC &&
                 cacheSize > std::max((9 * nTotalSpace) / 10,
                                      nTotalSpace -
                                          MAX_BLOCK_COINSDB_USAGE * 1024 * 1024);
             // The cache is over the limit, we have to write now.
             bool fCacheCritical =
                 mode == FlushStateMode::IF_NEEDED && cacheSize > nTotalSpace;
             // It's been a while since we wrote the block index to disk. Do this
             // frequently, so we don't need to redownload after a crash.
             bool fPeriodicWrite =
                 mode == FlushStateMode::PERIODIC &&
                 nNow > nLastWrite + (int64_t)DATABASE_WRITE_INTERVAL * 1000000;
             // It's been very long since we flushed the cache. Do this
             // infrequently, to optimize cache usage.
             bool fPeriodicFlush =
                 mode == FlushStateMode::PERIODIC &&
                 nNow > nLastFlush + (int64_t)DATABASE_FLUSH_INTERVAL * 1000000;
             // Combine all conditions that result in a full cache flush.
             fDoFullFlush = (mode == FlushStateMode::ALWAYS) || fCacheLarge ||
                            fCacheCritical || fPeriodicFlush || fFlushForPrune;
             // Write blocks and block index to disk.
             if (fDoFullFlush || fPeriodicWrite) {
                 // Depend on nMinDiskSpace to ensure we can write block index
                 if (!CheckDiskSpace(GetBlocksDir())) {
                     return AbortNode(state, "Disk space is low!",
                                      _("Error: Disk space is low!"));
                 }
 
                 // First make sure all block and undo data is flushed to disk.
                 FlushBlockFile();
                 // Then update all block file information (which may refer to
                 // block and undo files).
                 {
                     std::vector<std::pair<int, const CBlockFileInfo *>> vFiles;
                     vFiles.reserve(setDirtyFileInfo.size());
                     for (int i : setDirtyFileInfo) {
                         vFiles.push_back(std::make_pair(i, &vinfoBlockFile[i]));
                     }
 
                     setDirtyFileInfo.clear();
 
                     std::vector<const CBlockIndex *> vBlocks;
                     vBlocks.reserve(setDirtyBlockIndex.size());
                     for (const CBlockIndex *cbi : setDirtyBlockIndex) {
                         vBlocks.push_back(cbi);
                     }
 
                     setDirtyBlockIndex.clear();
 
                     if (!pblocktree->WriteBatchSync(vFiles, nLastBlockFile,
                                                     vBlocks)) {
                         return AbortNode(
                             state, "Failed to write to block index database");
                     }
                 }
 
                 // Finally remove any pruned files
                 if (fFlushForPrune) {
                     UnlinkPrunedFiles(setFilesToPrune);
                 }
                 nLastWrite = nNow;
             }
             // Flush best chain related state. This can only be done if the
             // blocks / block index write was also done.
             if (fDoFullFlush && !pcoinsTip->GetBestBlock().IsNull()) {
                 // Typical Coin structures on disk are around 48 bytes in size.
                 // Pushing a new one to the database can cause it to be written
                 // twice (once in the log, and once in the tables). This is
                 // already an overestimation, as most will delete an existing
                 // entry or overwrite one. Still, use a conservative safety
                 // factor of 2.
                 if (!CheckDiskSpace(GetDataDir(),
                                     48 * 2 * 2 * pcoinsTip->GetCacheSize())) {
                     return AbortNode(state, "Disk space is low!",
                                      _("Error: Disk space is low!"));
                 }
 
                 // Flush the chainstate (which may refer to block index
                 // entries).
                 if (!pcoinsTip->Flush()) {
                     return AbortNode(state, "Failed to write to coin database");
                 }
                 nLastFlush = nNow;
                 full_flush_completed = true;
             }
         }
 
         if (full_flush_completed) {
             // Update best block in wallet (so we can detect restored wallets).
             GetMainSignals().ChainStateFlushed(chainActive.GetLocator());
         }
     } catch (const std::runtime_error &e) {
         return AbortNode(state, std::string("System error while flushing: ") +
                                     e.what());
     }
     return true;
 }
 
 void FlushStateToDisk() {
     CValidationState state;
     const CChainParams &chainparams = Params();
     if (!FlushStateToDisk(chainparams, state, FlushStateMode::ALWAYS)) {
         LogPrintf("%s: failed to flush state (%s)\n", __func__,
                   FormatStateMessage(state));
     }
 }
 
 void PruneAndFlush() {
     CValidationState state;
     fCheckForPruning = true;
     const CChainParams &chainparams = Params();
     if (!FlushStateToDisk(chainparams, state, FlushStateMode::NONE)) {
         LogPrintf("%s: failed to flush state (%s)\n", __func__,
                   FormatStateMessage(state));
     }
 }
 
 /** Check warning conditions and do some notifications on new chain tip set. */
 static void UpdateTip(const Config &config, CBlockIndex *pindexNew) {
     // New best block
     g_mempool.AddTransactionsUpdated(1);
 
     {
         LOCK(g_best_block_mutex);
         g_best_block = pindexNew->GetBlockHash();
         g_best_block_cv.notify_all();
     }
 
     LogPrintf(
         "%s: new best=%s height=%d version=0x%08x log2_work=%.8g tx=%lu "
         "date='%s' progress=%f cache=%.1fMiB(%utxo)\n",
         __func__, pindexNew->GetBlockHash().ToString(), pindexNew->nHeight,
         pindexNew->nVersion, log(pindexNew->nChainWork.getdouble()) / log(2.0),
         (unsigned long)pindexNew->nChainTx,
         FormatISO8601DateTime(pindexNew->GetBlockTime()),
         GuessVerificationProgress(config.GetChainParams().TxData(), pindexNew),
         pcoinsTip->DynamicMemoryUsage() * (1.0 / (1 << 20)),
         pcoinsTip->GetCacheSize());
 }
 
 /**
  * Disconnect chainActive's tip.
  * After calling, the mempool will be in an inconsistent state, with
  * transactions from disconnected blocks being added to disconnectpool. You
  * should make the mempool consistent again by calling updateMempoolForReorg.
  * with cs_main held.
  *
  * If disconnectpool is nullptr, then no disconnected transactions are added to
  * disconnectpool (note that the caller is responsible for mempool consistency
  * in any case).
  */
 bool CChainState::DisconnectTip(const Config &config, CValidationState &state,
                                 DisconnectedBlockTransactions *disconnectpool) {
     AssertLockHeld(cs_main);
     CBlockIndex *pindexDelete = chainActive.Tip();
     const Consensus::Params &consensusParams =
         config.GetChainParams().GetConsensus();
 
     assert(pindexDelete);
 
     // Read block from disk.
     std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
     CBlock &block = *pblock;
     if (!ReadBlockFromDisk(block, pindexDelete, consensusParams)) {
         return AbortNode(state, "Failed to read block");
     }
 
     // Apply the block atomically to the chain state.
     int64_t nStart = GetTimeMicros();
     {
         CCoinsViewCache view(pcoinsTip.get());
         assert(view.GetBestBlock() == pindexDelete->GetBlockHash());
         if (DisconnectBlock(block, pindexDelete, view) != DISCONNECT_OK) {
             return error("DisconnectTip(): DisconnectBlock %s failed",
                          pindexDelete->GetBlockHash().ToString());
         }
 
         bool flushed = view.Flush();
         assert(flushed);
     }
 
     LogPrint(BCLog::BENCH, "- Disconnect block: %.2fms\n",
              (GetTimeMicros() - nStart) * MILLI);
 
     // Write the chain state to disk, if necessary.
     if (!FlushStateToDisk(config.GetChainParams(), state,
                           FlushStateMode::IF_NEEDED)) {
         return false;
     }
 
     // If this block is deactivating a fork, we move all mempool transactions
     // in front of disconnectpool for reprocessing in a future
     // updateMempoolForReorg call
     if (pindexDelete->pprev != nullptr &&
         GetNextBlockScriptFlags(consensusParams, pindexDelete) !=
             GetNextBlockScriptFlags(consensusParams, pindexDelete->pprev)) {
         LogPrint(BCLog::MEMPOOL,
                  "Disconnecting mempool due to rewind of upgrade block\n");
         if (disconnectpool) {
             disconnectpool->importMempool(g_mempool);
         }
         g_mempool.clear();
     }
 
     if (disconnectpool) {
         disconnectpool->addForBlock(block.vtx);
     }
 
     // If the tip is finalized, then undo it.
     if (pindexFinalized == pindexDelete) {
         pindexFinalized = pindexDelete->pprev;
     }
 
     chainActive.SetTip(pindexDelete->pprev);
 
     // Update chainActive and related variables.
     UpdateTip(config, pindexDelete->pprev);
     // Let wallets know transactions went from 1-confirmed to
     // 0-confirmed or conflicted:
     GetMainSignals().BlockDisconnected(pblock);
     return true;
 }
 
 static int64_t nTimeReadFromDisk = 0;
 static int64_t nTimeConnectTotal = 0;
 static int64_t nTimeFlush = 0;
 static int64_t nTimeChainState = 0;
 static int64_t nTimePostConnect = 0;
 
 struct PerBlockConnectTrace {
     CBlockIndex *pindex = nullptr;
     std::shared_ptr<const CBlock> pblock;
     std::shared_ptr<std::vector<CTransactionRef>> conflictedTxs;
     PerBlockConnectTrace()
         : conflictedTxs(std::make_shared<std::vector<CTransactionRef>>()) {}
 };
 
 /**
  * Used to track blocks whose transactions were applied to the UTXO state as a
  * part of a single ActivateBestChainStep call.
  *
  * This class also tracks transactions that are removed from the mempool as
  * conflicts (per block) and can be used to pass all those transactions through
  * SyncTransaction.
  *
  * This class assumes (and asserts) that the conflicted transactions for a given
  * block are added via mempool callbacks prior to the BlockConnected()
  * associated with those transactions. If any transactions are marked
  * conflicted, it is assumed that an associated block will always be added.
  *
  * This class is single-use, once you call GetBlocksConnected() you have to
  * throw it away and make a new one.
  */
 class ConnectTrace {
 private:
     std::vector<PerBlockConnectTrace> blocksConnected;
     CTxMemPool &pool;
     boost::signals2::scoped_connection m_connNotifyEntryRemoved;
 
 public:
     explicit ConnectTrace(CTxMemPool &_pool) : blocksConnected(1), pool(_pool) {
         m_connNotifyEntryRemoved = pool.NotifyEntryRemoved.connect(
             std::bind(&ConnectTrace::NotifyEntryRemoved, this,
                       std::placeholders::_1, std::placeholders::_2));
     }
 
     void BlockConnected(CBlockIndex *pindex,
                         std::shared_ptr<const CBlock> pblock) {
         assert(!blocksConnected.back().pindex);
         assert(pindex);
         assert(pblock);
         blocksConnected.back().pindex = pindex;
         blocksConnected.back().pblock = std::move(pblock);
         blocksConnected.emplace_back();
     }
 
     std::vector<PerBlockConnectTrace> &GetBlocksConnected() {
         // We always keep one extra block at the end of our list because blocks
         // are added after all the conflicted transactions have been filled in.
         // Thus, the last entry should always be an empty one waiting for the
         // transactions from the next block. We pop the last entry here to make
         // sure the list we return is sane.
         assert(!blocksConnected.back().pindex);
         assert(blocksConnected.back().conflictedTxs->empty());
         blocksConnected.pop_back();
         return blocksConnected;
     }
 
     void NotifyEntryRemoved(CTransactionRef txRemoved,
                             MemPoolRemovalReason reason) {
         assert(!blocksConnected.back().pindex);
         if (reason == MemPoolRemovalReason::CONFLICT) {
             blocksConnected.back().conflictedTxs->emplace_back(
                 std::move(txRemoved));
         }
     }
 };
 
 static bool FinalizeBlockInternal(const Config &config, CValidationState &state,
                                   const CBlockIndex *pindex)
     EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
     AssertLockHeld(cs_main);
     if (pindex->nStatus.isInvalid()) {
         // We try to finalize an invalid block.
         return state.DoS(100,
                          error("%s: Trying to finalize invalid block %s",
                                __func__, pindex->GetBlockHash().ToString()),
                          REJECT_INVALID, "finalize-invalid-block");
     }
 
     // Check that the request is consistent with current finalization.
     if (pindexFinalized && !AreOnTheSameFork(pindex, pindexFinalized)) {
         return state.DoS(
             20,
             error("%s: Trying to finalize block %s which conflicts "
                   "with already finalized block",
                   __func__, pindex->GetBlockHash().ToString()),
             REJECT_AGAINST_FINALIZED, "bad-fork-prior-finalized");
     }
 
     if (IsBlockFinalized(pindex)) {
         // The block is already finalized.
         return true;
     }
 
     // We have a new block to finalize.
     pindexFinalized = pindex;
     return true;
 }
 
 static const CBlockIndex *FindBlockToFinalize(const Config &config,
                                               CBlockIndex *pindexNew)
     EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
     AssertLockHeld(cs_main);
 
     const int32_t maxreorgdepth =
         gArgs.GetArg("-maxreorgdepth", DEFAULT_MAX_REORG_DEPTH);
 
     const int64_t finalizationdelay =
         gArgs.GetArg("-finalizationdelay", DEFAULT_MIN_FINALIZATION_DELAY);
 
     // Find our candidate.
     // If maxreorgdepth is < 0 pindex will be null and auto finalization
     // disabled
     const CBlockIndex *pindex =
         pindexNew->GetAncestor(pindexNew->nHeight - maxreorgdepth);
 
     int64_t now = GetTime();
 
     // If the finalization delay is not expired since the startup time,
     // finalization should be avoided. Header receive time is not saved to disk
     // and so cannot be anterior to startup time.
     if (now < (GetStartupTime() + finalizationdelay)) {
         return nullptr;
     }
 
     // While our candidate is not eligible (finalization delay not expired), try
     // the previous one.
     while (pindex && (pindex != pindexFinalized)) {
         // Check that the block to finalize is known for a long enough time.
         // This test will ensure that an attacker could not cause a block to
         // finalize by forking the chain with a depth > maxreorgdepth.
         // If the block is loaded from disk, header receive time is 0 and the
         // block will be finalized. This is safe because the delay since the
         // node startup is already expired.
         auto headerReceivedTime = pindex->GetHeaderReceivedTime();
 
         // If finalization delay is <= 0, finalization always occurs immediately
         if (now >= (headerReceivedTime + finalizationdelay)) {
             return pindex;
         }
 
         pindex = pindex->pprev;
     }
 
     return nullptr;
 }
 
 /**
  * Connect a new block to chainActive. pblock is either nullptr or a pointer to
  * a CBlock corresponding to pindexNew, to bypass loading it again from disk.
  *
  * The block is always added to connectTrace (either after loading from disk or
  * by copying pblock) - if that is not intended, care must be taken to remove
  * the last entry in blocksConnected in case of failure.
  */
 bool CChainState::ConnectTip(const Config &config, CValidationState &state,
                              CBlockIndex *pindexNew,
                              const std::shared_ptr<const CBlock> &pblock,
                              ConnectTrace &connectTrace,
                              DisconnectedBlockTransactions &disconnectpool) {
     AssertLockHeld(cs_main);
 
     const CChainParams &params = config.GetChainParams();
     const Consensus::Params &consensusParams = params.GetConsensus();
 
     assert(pindexNew->pprev == chainActive.Tip());
     // Read block from disk.
     int64_t nTime1 = GetTimeMicros();
     std::shared_ptr<const CBlock> pthisBlock;
     if (!pblock) {
         std::shared_ptr<CBlock> pblockNew = std::make_shared<CBlock>();
         if (!ReadBlockFromDisk(*pblockNew, pindexNew, consensusParams)) {
             return AbortNode(state, "Failed to read block");
         }
         pthisBlock = pblockNew;
     } else {
         pthisBlock = pblock;
     }
 
     const CBlock &blockConnecting = *pthisBlock;
 
     // Apply the block atomically to the chain state.
     int64_t nTime2 = GetTimeMicros();
     nTimeReadFromDisk += nTime2 - nTime1;
     int64_t nTime3;
     LogPrint(BCLog::BENCH, "  - Load block from disk: %.2fms [%.2fs]\n",
              (nTime2 - nTime1) * MILLI, nTimeReadFromDisk * MICRO);
     {
         CCoinsViewCache view(pcoinsTip.get());
         bool rv = ConnectBlock(blockConnecting, state, pindexNew, view, params,
                                BlockValidationOptions(config));
         GetMainSignals().BlockChecked(blockConnecting, state);
         if (!rv) {
             if (state.IsInvalid()) {
                 InvalidBlockFound(pindexNew, state);
             }
 
             return error("ConnectTip(): ConnectBlock %s failed (%s)",
                          pindexNew->GetBlockHash().ToString(),
                          FormatStateMessage(state));
         }
 
         // Update the finalized block.
         const CBlockIndex *pindexToFinalize =
             FindBlockToFinalize(config, pindexNew);
         if (pindexToFinalize &&
             !FinalizeBlockInternal(config, state, pindexToFinalize)) {
             state.SetCorruptionPossible();
             return error("ConnectTip(): FinalizeBlock %s failed (%s)",
                          pindexNew->GetBlockHash().ToString(),
                          FormatStateMessage(state));
         }
 
         nTime3 = GetTimeMicros();
         nTimeConnectTotal += nTime3 - nTime2;
         LogPrint(BCLog::BENCH,
                  "  - Connect total: %.2fms [%.2fs (%.2fms/blk)]\n",
                  (nTime3 - nTime2) * MILLI, nTimeConnectTotal * MICRO,
                  nTimeConnectTotal * MILLI / nBlocksTotal);
         bool flushed = view.Flush();
         assert(flushed);
     }
 
     int64_t nTime4 = GetTimeMicros();
     nTimeFlush += nTime4 - nTime3;
     LogPrint(BCLog::BENCH, "  - Flush: %.2fms [%.2fs (%.2fms/blk)]\n",
              (nTime4 - nTime3) * MILLI, nTimeFlush * MICRO,
              nTimeFlush * MILLI / nBlocksTotal);
 
     // Write the chain state to disk, if necessary.
     if (!FlushStateToDisk(config.GetChainParams(), state,
                           FlushStateMode::IF_NEEDED)) {
         return false;
     }
 
     int64_t nTime5 = GetTimeMicros();
     nTimeChainState += nTime5 - nTime4;
     LogPrint(BCLog::BENCH,
              "  - Writing chainstate: %.2fms [%.2fs (%.2fms/blk)]\n",
              (nTime5 - nTime4) * MILLI, nTimeChainState * MICRO,
              nTimeChainState * MILLI / nBlocksTotal);
 
     // Remove conflicting transactions from the mempool.;
     g_mempool.removeForBlock(blockConnecting.vtx, pindexNew->nHeight);
     disconnectpool.removeForBlock(blockConnecting.vtx);
 
     // If this block is activating a fork, we move all mempool transactions
     // in front of disconnectpool for reprocessing in a future
     // updateMempoolForReorg call
     if (pindexNew->pprev != nullptr &&
         GetNextBlockScriptFlags(consensusParams, pindexNew) !=
             GetNextBlockScriptFlags(consensusParams, pindexNew->pprev)) {
         LogPrint(BCLog::MEMPOOL,
                  "Disconnecting mempool due to acceptance of upgrade block\n");
         disconnectpool.importMempool(g_mempool);
     }
 
     // Update chainActive & related variables.
     chainActive.SetTip(pindexNew);
     UpdateTip(config, pindexNew);
 
     int64_t nTime6 = GetTimeMicros();
     nTimePostConnect += nTime6 - nTime5;
     nTimeTotal += nTime6 - nTime1;
     LogPrint(BCLog::BENCH,
              "  - Connect postprocess: %.2fms [%.2fs (%.2fms/blk)]\n",
              (nTime6 - nTime5) * MILLI, nTimePostConnect * MICRO,
              nTimePostConnect * MILLI / nBlocksTotal);
     LogPrint(BCLog::BENCH, "- Connect block: %.2fms [%.2fs (%.2fms/blk)]\n",
              (nTime6 - nTime1) * MILLI, nTimeTotal * MICRO,
              nTimeTotal * MILLI / nBlocksTotal);
 
     connectTrace.BlockConnected(pindexNew, std::move(pthisBlock));
     return true;
 }
 
 /**
  * Return the tip of the chain with the most work in it, that isn't known to be
  * invalid (it's however far from certain to be valid).
  */
 CBlockIndex *CChainState::FindMostWorkChain() {
     AssertLockHeld(cs_main);
     do {
         CBlockIndex *pindexNew = nullptr;
 
         // Find the best candidate header.
         {
             std::set<CBlockIndex *, CBlockIndexWorkComparator>::reverse_iterator
                 it = setBlockIndexCandidates.rbegin();
             if (it == setBlockIndexCandidates.rend()) {
                 return nullptr;
             }
             pindexNew = *it;
         }
 
         // If this block will cause a finalized block to be reorged, then we
         // mark it as invalid.
         if (pindexFinalized && !AreOnTheSameFork(pindexNew, pindexFinalized)) {
             LogPrintf("Mark block %s invalid because it forks prior to the "
                       "finalization point %d.\n",
                       pindexNew->GetBlockHash().ToString(),
                       pindexFinalized->nHeight);
             pindexNew->nStatus = pindexNew->nStatus.withFailed();
             InvalidChainFound(pindexNew);
         }
 
         const CBlockIndex *pindexFork = chainActive.FindFork(pindexNew);
 
         // Check whether all blocks on the path between the currently active
         // chain and the candidate are valid. Just going until the active chain
         // is an optimization, as we know all blocks in it are valid already.
         CBlockIndex *pindexTest = pindexNew;
         bool hasValidAncestor = true;
         while (hasValidAncestor && pindexTest && pindexTest != pindexFork) {
             assert(pindexTest->HaveTxsDownloaded() || pindexTest->nHeight == 0);
 
             // If this is a parked chain, but it has enough PoW, clear the park
             // state.
             bool fParkedChain = pindexTest->nStatus.isOnParkedChain();
             if (fParkedChain && gArgs.GetBoolArg("-automaticunparking", true)) {
                 const CBlockIndex *pindexTip = chainActive.Tip();
 
                 // During initialization, pindexTip and/or pindexFork may be
                 // null. In this case, we just ignore the fact that the chain is
                 // parked.
                 if (!pindexTip || !pindexFork) {
                     UnparkBlock(pindexTest);
                     continue;
                 }
 
                 // A parked chain can be unparked if it has twice as much PoW
                 // accumulated as the main chain has since the fork block.
                 CBlockIndex const *pindexExtraPow = pindexTip;
                 arith_uint256 requiredWork = pindexTip->nChainWork;
                 switch (pindexTip->nHeight - pindexFork->nHeight) {
                     // Limit the penality for depth 1, 2 and 3 to half a block
                     // worth of work to ensure we don't fork accidentally.
                     case 3:
                     case 2:
                         pindexExtraPow = pindexExtraPow->pprev;
                     // FALLTHROUGH
                     case 1: {
                         const arith_uint256 deltaWork =
                             pindexExtraPow->nChainWork - pindexFork->nChainWork;
                         requiredWork += (deltaWork >> 1);
                         break;
                     }
                     default:
                         requiredWork +=
                             pindexExtraPow->nChainWork - pindexFork->nChainWork;
                         break;
                 }
 
                 if (pindexNew->nChainWork > requiredWork) {
                     // We have enough, clear the parked state.
                     LogPrintf("Unpark chain up to block %s as it has "
                               "accumulated enough PoW.\n",
                               pindexNew->GetBlockHash().ToString());
                     fParkedChain = false;
                     UnparkBlock(pindexTest);
                 }
             }
 
             // Pruned nodes may have entries in setBlockIndexCandidates for
             // which block files have been deleted. Remove those as candidates
             // for the most work chain if we come across them; we can't switch
             // to a chain unless we have all the non-active-chain parent blocks.
             bool fInvalidChain = pindexTest->nStatus.isInvalid();
             bool fMissingData = !pindexTest->nStatus.hasData();
             if (!(fInvalidChain || fParkedChain || fMissingData)) {
                 // The current block is acceptable, move to the parent, up to
                 // the fork point.
                 pindexTest = pindexTest->pprev;
                 continue;
             }
 
             // Candidate chain is not usable (either invalid or parked or
             // missing data)
             hasValidAncestor = false;
             setBlockIndexCandidates.erase(pindexTest);
 
             if (fInvalidChain &&
                 (pindexBestInvalid == nullptr ||
                  pindexNew->nChainWork > pindexBestInvalid->nChainWork)) {
                 pindexBestInvalid = pindexNew;
             }
 
             if (fParkedChain &&
                 (pindexBestParked == nullptr ||
                  pindexNew->nChainWork > pindexBestParked->nChainWork)) {
                 pindexBestParked = pindexNew;
             }
 
             LogPrintf("Considered switching to better tip %s but that chain "
                       "contains a%s%s%s block.\n",
                       pindexNew->GetBlockHash().ToString(),
                       fInvalidChain ? "n invalid" : "",
                       fParkedChain ? " parked" : "",
                       fMissingData ? " missing-data" : "");
 
             CBlockIndex *pindexFailed = pindexNew;
             // Remove the entire chain from the set.
             while (pindexTest != pindexFailed) {
                 if (fInvalidChain || fParkedChain) {
                     pindexFailed->nStatus =
                         pindexFailed->nStatus.withFailedParent(fInvalidChain)
                             .withParkedParent(fParkedChain);
                 } else if (fMissingData) {
                     // If we're missing data, then add back to
                     // mapBlocksUnlinked, so that if the block arrives in the
                     // future we can try adding to setBlockIndexCandidates
                     // again.
                     mapBlocksUnlinked.insert(
                         std::make_pair(pindexFailed->pprev, pindexFailed));
                 }
                 setBlockIndexCandidates.erase(pindexFailed);
                 pindexFailed = pindexFailed->pprev;
             }
 
             if (fInvalidChain || fParkedChain) {
                 // We discovered a new chain tip that is either parked or
                 // invalid, we may want to warn.
                 CheckForkWarningConditionsOnNewFork(pindexNew);
             }
         }
 
         // We found a candidate that has valid ancestors. This is our guy.
         if (hasValidAncestor) {
             return pindexNew;
         }
     } while (true);
 }
 
 /**
  * Delete all entries in setBlockIndexCandidates that are worse than the current
  * tip.
  */
 void CChainState::PruneBlockIndexCandidates() {
     // Note that we can't delete the current block itself, as we may need to
     // return to it later in case a reorganization to a better block fails.
     auto it = setBlockIndexCandidates.begin();
     while (it != setBlockIndexCandidates.end() &&
            setBlockIndexCandidates.value_comp()(*it, chainActive.Tip())) {
         setBlockIndexCandidates.erase(it++);
     }
 
     // Either the current tip or a successor of it we're working towards is left
     // in setBlockIndexCandidates.
     assert(!setBlockIndexCandidates.empty());
 }
 
 /**
  * Try to make some progress towards making pindexMostWork the active block.
  * pblock is either nullptr or a pointer to a CBlock corresponding to
  * pindexMostWork.
  */
 bool CChainState::ActivateBestChainStep(
     const Config &config, CValidationState &state, CBlockIndex *pindexMostWork,
     const std::shared_ptr<const CBlock> &pblock, bool &fInvalidFound,
     ConnectTrace &connectTrace) {
     AssertLockHeld(cs_main);
 
     const CBlockIndex *pindexOldTip = chainActive.Tip();
     const CBlockIndex *pindexFork = chainActive.FindFork(pindexMostWork);
 
     // Disconnect active blocks which are no longer in the best chain.
     bool fBlocksDisconnected = false;
     DisconnectedBlockTransactions disconnectpool;
     while (chainActive.Tip() && chainActive.Tip() != pindexFork) {
         if (!DisconnectTip(config, state, &disconnectpool)) {
             // This is likely a fatal error, but keep the mempool consistent,
             // just in case. Only remove from the mempool in this case.
             disconnectpool.updateMempoolForReorg(config, false);
             return false;
         }
 
         fBlocksDisconnected = true;
     }
 
     // Build list of new blocks to connect.
     std::vector<CBlockIndex *> vpindexToConnect;
     bool fContinue = true;
     int nHeight = pindexFork ? pindexFork->nHeight : -1;
     while (fContinue && nHeight != pindexMostWork->nHeight) {
         // Don't iterate the entire list of potential improvements toward the
         // best tip, as we likely only need a few blocks along the way.
         int nTargetHeight = std::min(nHeight + 32, pindexMostWork->nHeight);
         vpindexToConnect.clear();
         vpindexToConnect.reserve(nTargetHeight - nHeight);
         CBlockIndex *pindexIter = pindexMostWork->GetAncestor(nTargetHeight);
         while (pindexIter && pindexIter->nHeight != nHeight) {
             vpindexToConnect.push_back(pindexIter);
             pindexIter = pindexIter->pprev;
         }
 
         nHeight = nTargetHeight;
 
         // Connect new blocks.
         for (CBlockIndex *pindexConnect : reverse_iterate(vpindexToConnect)) {
             if (!ConnectTip(config, state, pindexConnect,
                             pindexConnect == pindexMostWork
                                 ? pblock
                                 : std::shared_ptr<const CBlock>(),
                             connectTrace, disconnectpool)) {
                 if (state.IsInvalid()) {
                     // The block violates a consensus rule.
                     if (!state.CorruptionPossible()) {
                         InvalidChainFound(vpindexToConnect.back());
                     }
 
                     state = CValidationState();
                     fInvalidFound = true;
                     fContinue = false;
                     break;
                 }
 
                 // A system error occurred (disk space, database error, ...).
                 // Make the mempool consistent with the current tip, just in
                 // case any observers try to use it before shutdown.
                 disconnectpool.updateMempoolForReorg(config, false);
                 return false;
             } else {
                 PruneBlockIndexCandidates();
                 if (!pindexOldTip ||
                     chainActive.Tip()->nChainWork > pindexOldTip->nChainWork) {
                     // We're in a better position than we were. Return
                     // temporarily to release the lock.
                     fContinue = false;
                     break;
                 }
             }
         }
     }
 
     if (fBlocksDisconnected || !disconnectpool.isEmpty()) {
         // If any blocks were disconnected, we need to update the mempool even
         // if disconnectpool is empty. The disconnectpool may also be non-empty
         // if the mempool was imported due to new validation rules being in
         // effect.
         LogPrint(BCLog::MEMPOOL, "Updating mempool due to reorganization or "
                                  "rules upgrade/downgrade\n");
         disconnectpool.updateMempoolForReorg(config, true);
     }
 
     g_mempool.check(pcoinsTip.get());
 
     // Callbacks/notifications for a new best chain.
     if (fInvalidFound) {
         CheckForkWarningConditionsOnNewFork(pindexMostWork);
     } else {
         CheckForkWarningConditions();
     }
 
     return true;
 }
 
 static void NotifyHeaderTip() LOCKS_EXCLUDED(cs_main) {
     bool fNotify = false;
     bool fInitialBlockDownload = false;
     static CBlockIndex *pindexHeaderOld = nullptr;
     CBlockIndex *pindexHeader = nullptr;
     {
         LOCK(cs_main);
         pindexHeader = pindexBestHeader;
 
         if (pindexHeader != pindexHeaderOld) {
             fNotify = true;
             fInitialBlockDownload = IsInitialBlockDownload();
             pindexHeaderOld = pindexHeader;
         }
     }
 
     // Send block tip changed notifications without cs_main
     if (fNotify) {
         uiInterface.NotifyHeaderTip(fInitialBlockDownload, pindexHeader);
     }
 }
 
 /**
  * Make the best chain active, in multiple steps. The result is either failure
  * or an activated best chain. pblock is either nullptr or a pointer to a block
  * that is already loaded (to avoid loading it again from disk).
  *
  * ActivateBestChain is split into steps (see ActivateBestChainStep) so that
  * we avoid holding cs_main for an extended period of time; the length of this
  * call may be quite long during reindexing or a substantial reorg.
  */
 bool CChainState::ActivateBestChain(const Config &config,
                                     CValidationState &state,
                                     std::shared_ptr<const CBlock> pblock) {
     // Note that while we're often called here from ProcessNewBlock, this is
     // far from a guarantee. Things in the P2P/RPC will often end up calling
     // us in the middle of ProcessNewBlock - do not assume pblock is set
     // sanely for performance or correctness!
     AssertLockNotHeld(cs_main);
 
     const CChainParams &params = config.GetChainParams();
 
     // ABC maintains a fair degree of expensive-to-calculate internal state
     // because this function periodically releases cs_main so that it does not
     // lock up other threads for too long during large connects - and to allow
     // for e.g. the callback queue to drain we use m_cs_chainstate to enforce
     // mutual exclusion so that only one caller may execute this function at a
     // time
     LOCK(m_cs_chainstate);
 
     CBlockIndex *pindexMostWork = nullptr;
     CBlockIndex *pindexNewTip = nullptr;
     int nStopAtHeight = gArgs.GetArg("-stopatheight", DEFAULT_STOPATHEIGHT);
     do {
         boost::this_thread::interruption_point();
 
         if (GetMainSignals().CallbacksPending() > 10) {
             // Block until the validation queue drains. This should largely
             // never happen in normal operation, however may happen during
             // reindex, causing memory blowup if we run too far ahead.
             // Note that if a validationinterface callback ends up calling
             // ActivateBestChain this may lead to a deadlock! We should
             // probably have a DEBUG_LOCKORDER test for this in the future.
             SyncWithValidationInterfaceQueue();
         }
 
         {
             LOCK(cs_main);
             CBlockIndex *starting_tip = chainActive.Tip();
             bool blocks_connected = false;
             do {
                 // We absolutely may not unlock cs_main until we've made forward
                 // progress (with the exception of shutdown due to hardware
                 // issues, low disk space, etc).
 
                 // Destructed before cs_main is unlocked
                 ConnectTrace connectTrace(g_mempool);
 
                 if (pindexMostWork == nullptr) {
                     pindexMostWork = FindMostWorkChain();
                 }
 
                 // Whether we have anything to do at all.
                 if (pindexMostWork == nullptr ||
                     pindexMostWork == chainActive.Tip()) {
                     break;
                 }
 
                 bool fInvalidFound = false;
                 std::shared_ptr<const CBlock> nullBlockPtr;
                 if (!ActivateBestChainStep(
                         config, state, pindexMostWork,
                         pblock && pblock->GetHash() ==
                                       pindexMostWork->GetBlockHash()
                             ? pblock
                             : nullBlockPtr,
                         fInvalidFound, connectTrace)) {
                     return false;
                 }
                 blocks_connected = true;
 
                 if (fInvalidFound) {
                     // Wipe cache, we may need another branch now.
                     pindexMostWork = nullptr;
                 }
 
                 pindexNewTip = chainActive.Tip();
                 for (const PerBlockConnectTrace &trace :
                      connectTrace.GetBlocksConnected()) {
                     assert(trace.pblock && trace.pindex);
                     GetMainSignals().BlockConnected(trace.pblock, trace.pindex,
                                                     trace.conflictedTxs);
                 }
             } while (!chainActive.Tip() ||
                      (starting_tip && CBlockIndexWorkComparator()(
                                           chainActive.Tip(), starting_tip)));
 
             // Check the index once we're done with the above loop, since
             // we're going to release cs_main soon. If the index is in a bad
             // state now, then it's better to know immediately rather than
             // randomly have it cause a problem in a race.
             CheckBlockIndex(params.GetConsensus());
 
             if (!blocks_connected) {
                 return true;
             }
 
             const CBlockIndex *pindexFork = chainActive.FindFork(starting_tip);
             bool fInitialDownload = IsInitialBlockDownload();
 
             // Notify external listeners about the new tip.
             // Enqueue while holding cs_main to ensure that UpdatedBlockTip is
             // called in the order in which blocks are connected
             if (pindexFork != pindexNewTip) {
                 // Notify ValidationInterface subscribers
                 GetMainSignals().UpdatedBlockTip(pindexNewTip, pindexFork,
                                                  fInitialDownload);
 
                 // Always notify the UI if a new block tip was connected
                 uiInterface.NotifyBlockTip(fInitialDownload, pindexNewTip);
             }
         }
         // When we reach this point, we switched to a new tip (stored in
         // pindexNewTip).
 
         if (nStopAtHeight && pindexNewTip &&
             pindexNewTip->nHeight >= nStopAtHeight) {
             StartShutdown();
         }
 
         // We check shutdown only after giving ActivateBestChainStep a chance to
         // run once so that we never shutdown before connecting the genesis
         // block during LoadChainTip(). Previously this caused an assert()
         // failure during shutdown in such cases as the UTXO DB flushing checks
         // that the best block hash is non-null.
         if (ShutdownRequested()) {
             break;
         }
     } while (pindexNewTip != pindexMostWork);
 
     // Write changes periodically to disk, after relay.
     if (!FlushStateToDisk(params, state, FlushStateMode::PERIODIC)) {
         return false;
     }
 
     return true;
 }
 
 bool ActivateBestChain(const Config &config, CValidationState &state,
                        std::shared_ptr<const CBlock> pblock) {
     return g_chainstate.ActivateBestChain(config, state, std::move(pblock));
 }
 
 bool CChainState::PreciousBlock(const Config &config, CValidationState &state,
                                 CBlockIndex *pindex) {
     {
         LOCK(cs_main);
         if (pindex->nChainWork < chainActive.Tip()->nChainWork) {
             // Nothing to do, this block is not at the tip.
             return true;
         }
 
         if (chainActive.Tip()->nChainWork > nLastPreciousChainwork) {
             // The chain has been extended since the last call, reset the
             // counter.
             nBlockReverseSequenceId = -1;
         }
 
         nLastPreciousChainwork = chainActive.Tip()->nChainWork;
         setBlockIndexCandidates.erase(pindex);
         pindex->nSequenceId = nBlockReverseSequenceId;
         if (nBlockReverseSequenceId > std::numeric_limits<int32_t>::min()) {
             // We can't keep reducing the counter if somebody really wants to
             // call preciousblock 2**31-1 times on the same set of tips...
             nBlockReverseSequenceId--;
         }
 
         // In case this was parked, unpark it.
         UnparkBlock(pindex);
 
         // Make sure it is added to the candidate list if appropriate.
         if (pindex->IsValid(BlockValidity::TRANSACTIONS) &&
             pindex->HaveTxsDownloaded()) {
             setBlockIndexCandidates.insert(pindex);
             PruneBlockIndexCandidates();
         }
     }
 
     return ActivateBestChain(config, state);
 }
 
 bool PreciousBlock(const Config &config, CValidationState &state,
                    CBlockIndex *pindex) {
     return g_chainstate.PreciousBlock(config, state, pindex);
 }
 
 bool CChainState::UnwindBlock(const Config &config, CValidationState &state,
                               CBlockIndex *pindex, bool invalidate) {
     CBlockIndex *to_mark_failed_or_parked = pindex;
     bool pindex_was_in_chain = false;
     int disconnected = 0;
 
     // Disconnect (descendants of) pindex, and mark them invalid.
     while (true) {
         if (ShutdownRequested()) {
             break;
         }
 
         LOCK(cs_main);
 
         if (!chainActive.Contains(pindex)) {
             break;
         }
 
         pindex_was_in_chain = true;
         CBlockIndex *invalid_walk_tip = chainActive.Tip();
 
         // ActivateBestChain considers blocks already in chainActive
         // unconditionally valid already, so force disconnect away from it.
 
         DisconnectedBlockTransactions disconnectpool;
 
         bool ret = DisconnectTip(config, state, &disconnectpool);
 
         // DisconnectTip will add transactions to disconnectpool.
         // Adjust the mempool to be consistent with the new tip, adding
         // transactions back to the mempool if disconnecting was successful,
         // and we're not doing a very deep invalidation (in which case
         // keeping the mempool up to date is probably futile anyway).
         disconnectpool.updateMempoolForReorg(
             config, /* fAddToMempool = */ (++disconnected <= 10) && ret);
 
         if (!ret) {
             return false;
         }
 
         assert(invalid_walk_tip->pprev == chainActive.Tip());
 
         // We immediately mark the disconnected blocks as invalid.
         // This prevents a case where pruned nodes may fail to invalidateblock
         // and be left unable to start as they have no tip candidates (as there
         // are no blocks that meet the "have data and are not invalid per
         // nStatus" criteria for inclusion in setBlockIndexCandidates).
 
         invalid_walk_tip->nStatus =
             invalidate ? invalid_walk_tip->nStatus.withFailed()
                        : invalid_walk_tip->nStatus.withParked();
 
         setDirtyBlockIndex.insert(invalid_walk_tip);
         setBlockIndexCandidates.insert(invalid_walk_tip->pprev);
 
         if (invalid_walk_tip == to_mark_failed_or_parked->pprev &&
             (invalidate ? to_mark_failed_or_parked->nStatus.hasFailed()
                         : to_mark_failed_or_parked->nStatus.isParked())) {
             // We only want to mark the last disconnected block as
             // Failed (or Parked); its children need to be FailedParent (or
             // ParkedParent) instead.
             to_mark_failed_or_parked->nStatus =
                 (invalidate
                      ? to_mark_failed_or_parked->nStatus.withFailed(false)
                            .withFailedParent()
                      : to_mark_failed_or_parked->nStatus.withParked(false)
                            .withParkedParent());
 
             setDirtyBlockIndex.insert(to_mark_failed_or_parked);
         }
 
         // Track the last disconnected block, so we can correct its
         // FailedParent (or ParkedParent) status in future iterations, or, if
         // it's the last one, call InvalidChainFound on it.
         to_mark_failed_or_parked = invalid_walk_tip;
     }
 
     {
         LOCK(cs_main);
         if (chainActive.Contains(to_mark_failed_or_parked)) {
             // If the to-be-marked invalid block is in the active chain,
             // something is interfering and we can't proceed.
             return false;
         }
 
         // Mark pindex (or the last disconnected block) as invalid (or parked),
         // even when it never was in the main chain.
         to_mark_failed_or_parked->nStatus =
             invalidate ? to_mark_failed_or_parked->nStatus.withFailed()
                        : to_mark_failed_or_parked->nStatus.withParked();
         setDirtyBlockIndex.insert(to_mark_failed_or_parked);
         if (invalidate) {
             m_failed_blocks.insert(to_mark_failed_or_parked);
         }
 
         // The resulting new best tip may not be in setBlockIndexCandidates
         // anymore, so add it again.
         for (const std::pair<const BlockHash, CBlockIndex *> &it :
              mapBlockIndex) {
             CBlockIndex *i = it.second;
             if (i->IsValid(BlockValidity::TRANSACTIONS) &&
                 i->HaveTxsDownloaded() &&
                 !setBlockIndexCandidates.value_comp()(i, chainActive.Tip())) {
                 setBlockIndexCandidates.insert(i);
             }
         }
 
         if (invalidate) {
             InvalidChainFound(to_mark_failed_or_parked);
         }
     }
 
     // Only notify about a new block tip if the active chain was modified.
     if (pindex_was_in_chain) {
         uiInterface.NotifyBlockTip(IsInitialBlockDownload(),
                                    to_mark_failed_or_parked->pprev);
     }
     return true;
 }
 
 bool FinalizeBlockAndInvalidate(const Config &config, CValidationState &state,
                                 CBlockIndex *pindex) {
     AssertLockHeld(cs_main);
     if (!FinalizeBlockInternal(config, state, pindex)) {
         // state is set by FinalizeBlockInternal.
         return false;
     }
 
     // We have a valid candidate, make sure it is not parked.
     if (pindex->nStatus.isOnParkedChain()) {
         UnparkBlock(pindex);
     }
 
     // If the finalized block is not on the active chain, we may need to rewind.
     if (!chainActive.Contains(pindex)) {
         const CBlockIndex *pindexFork = chainActive.FindFork(pindex);
         CBlockIndex *pindexToInvalidate = chainActive.Next(pindexFork);
         if (pindexToInvalidate) {
             return InvalidateBlock(config, state, pindexToInvalidate);
         }
     }
 
     return true;
 }
 
 bool InvalidateBlock(const Config &config, CValidationState &state,
                      CBlockIndex *pindex) {
     return g_chainstate.UnwindBlock(config, state, pindex, true);
 }
 
 bool ParkBlock(const Config &config, CValidationState &state,
                CBlockIndex *pindex) {
     return g_chainstate.UnwindBlock(config, state, pindex, false);
 }
 
 template <typename F>
 void CChainState::UpdateFlagsForBlock(CBlockIndex *pindexBase,
                                       CBlockIndex *pindex, F f) {
     BlockStatus newStatus = f(pindex->nStatus);
     if (pindex->nStatus != newStatus &&
         (!pindexBase ||
          pindex->GetAncestor(pindexBase->nHeight) == pindexBase)) {
         pindex->nStatus = newStatus;
         setDirtyBlockIndex.insert(pindex);
         if (newStatus.isValid()) {
             m_failed_blocks.erase(pindex);
         }
 
         if (pindex->IsValid(BlockValidity::TRANSACTIONS) &&
             pindex->HaveTxsDownloaded() &&
             setBlockIndexCandidates.value_comp()(chainActive.Tip(), pindex)) {
             setBlockIndexCandidates.insert(pindex);
         }
     }
 }
 
 template <typename F, typename C>
 void CChainState::UpdateFlags(CBlockIndex *pindex, F f, C fchild) {
     AssertLockHeld(cs_main);
 
     // Update the current block.
     UpdateFlagsForBlock(pindex, pindex, f);
 
     // Update the flags from this block and all its descendants.
     BlockMap::iterator it = mapBlockIndex.begin();
     while (it != mapBlockIndex.end()) {
         UpdateFlagsForBlock(pindex, it->second, fchild);
         it++;
     }
 
     // Update the flags from all ancestors too.
     while (pindex != nullptr) {
         UpdateFlagsForBlock(nullptr, pindex, f);
         pindex = pindex->pprev;
     }
 }
 
 template <typename F> void CChainState::UpdateFlags(CBlockIndex *pindex, F f) {
     // Handy shorthand.
     UpdateFlags(pindex, f, f);
 }
 
 void CChainState::ResetBlockFailureFlags(CBlockIndex *pindex) {
     AssertLockHeld(cs_main);
 
     if (pindexBestInvalid &&
         (pindexBestInvalid->GetAncestor(pindex->nHeight) == pindex ||
          pindex->GetAncestor(pindexBestInvalid->nHeight) ==
              pindexBestInvalid)) {
         // Reset the invalid block marker if it is about to be cleared.
         pindexBestInvalid = nullptr;
     }
 
     // In case we are reconsidering something before the finalization point,
     // move the finalization point to the last common ancestor.
     if (pindexFinalized) {
         pindexFinalized = LastCommonAncestor(pindex, pindexFinalized);
     }
 
     UpdateFlags(pindex, [](const BlockStatus status) {
         return status.withClearedFailureFlags();
     });
 }
 
 void ResetBlockFailureFlags(CBlockIndex *pindex) {
     return g_chainstate.ResetBlockFailureFlags(pindex);
 }
 
 void CChainState::UnparkBlockImpl(CBlockIndex *pindex, bool fClearChildren) {
     AssertLockHeld(cs_main);
 
     if (pindexBestParked &&
         (pindexBestParked->GetAncestor(pindex->nHeight) == pindex ||
          pindex->GetAncestor(pindexBestParked->nHeight) == pindexBestParked)) {
         // Reset the parked block marker if it is about to be cleared.
         pindexBestParked = nullptr;
     }
 
     UpdateFlags(
         pindex,
         [](const BlockStatus status) {
             return status.withClearedParkedFlags();
         },
         [fClearChildren](const BlockStatus status) {
             return fClearChildren ? status.withClearedParkedFlags()
                                   : status.withParkedParent(false);
         });
 }
 
 void UnparkBlockAndChildren(CBlockIndex *pindex) {
     return g_chainstate.UnparkBlockImpl(pindex, true);
 }
 
 void UnparkBlock(CBlockIndex *pindex) {
     return g_chainstate.UnparkBlockImpl(pindex, false);
 }
 
 const CBlockIndex *GetFinalizedBlock() {
     AssertLockHeld(cs_main);
     return pindexFinalized;
 }
 
 bool IsBlockFinalized(const CBlockIndex *pindex) {
     AssertLockHeld(cs_main);
     return pindexFinalized &&
            pindexFinalized->GetAncestor(pindex->nHeight) == pindex;
 }
 
 CBlockIndex *CChainState::AddToBlockIndex(const CBlockHeader &block) {
     AssertLockHeld(cs_main);
 
     // Check for duplicate
     BlockHash hash = block.GetHash();
     BlockMap::iterator it = mapBlockIndex.find(hash);
     if (it != mapBlockIndex.end()) {
         return it->second;
     }
 
     // Construct new block index object
     CBlockIndex *pindexNew = new CBlockIndex(block);
     // We assign the sequence id to blocks only when the full data is available,
     // to avoid miners withholding blocks but broadcasting headers, to get a
     // competitive advantage.
     pindexNew->nSequenceId = 0;
     BlockMap::iterator mi =
         mapBlockIndex.insert(std::make_pair(hash, pindexNew)).first;
     pindexNew->phashBlock = &((*mi).first);
     BlockMap::iterator miPrev = mapBlockIndex.find(block.hashPrevBlock);
     if (miPrev != mapBlockIndex.end()) {
         pindexNew->pprev = (*miPrev).second;
         pindexNew->nHeight = pindexNew->pprev->nHeight + 1;
         pindexNew->BuildSkip();
     }
     pindexNew->nTimeReceived = GetTime();
     pindexNew->nTimeMax =
         (pindexNew->pprev
              ? std::max(pindexNew->pprev->nTimeMax, pindexNew->nTime)
              : pindexNew->nTime);
     pindexNew->nChainWork =
         (pindexNew->pprev ? pindexNew->pprev->nChainWork : 0) +
         GetBlockProof(*pindexNew);
     pindexNew->RaiseValidity(BlockValidity::TREE);
     if (pindexBestHeader == nullptr ||
         pindexBestHeader->nChainWork < pindexNew->nChainWork) {
         pindexBestHeader = pindexNew;
     }
 
     setDirtyBlockIndex.insert(pindexNew);
     return pindexNew;
 }
 
 /**
  * Mark a block as having its data received and checked (up to
  * BLOCK_VALID_TRANSACTIONS).
  */
 void CChainState::ReceivedBlockTransactions(const CBlock &block,
                                             CBlockIndex *pindexNew,
                                             const FlatFilePos &pos) {
     pindexNew->nTx = block.vtx.size();
     pindexNew->nChainTx = 0;
     pindexNew->nFile = pos.nFile;
     pindexNew->nDataPos = pos.nPos;
     pindexNew->nUndoPos = 0;
     pindexNew->nStatus = pindexNew->nStatus.withData();
     pindexNew->RaiseValidity(BlockValidity::TRANSACTIONS);
     setDirtyBlockIndex.insert(pindexNew);
 
     if (pindexNew->pprev == nullptr || pindexNew->pprev->HaveTxsDownloaded()) {
         // If pindexNew is the genesis block or all parents are
         // BLOCK_VALID_TRANSACTIONS.
         std::deque<CBlockIndex *> queue;
         queue.push_back(pindexNew);
 
         // Recursively process any descendant blocks that now may be eligible to
         // be connected.
         while (!queue.empty()) {
             CBlockIndex *pindex = queue.front();
             queue.pop_front();
             pindex->nChainTx =
                 (pindex->pprev ? pindex->pprev->nChainTx : 0) + pindex->nTx;
             if (pindex->nSequenceId == 0) {
                 // We assign a sequence is when transaction are received to
                 // prevent a miner from being able to broadcast a block but not
                 // its content. However, a sequence id may have been set
                 // manually, for instance via PreciousBlock, in which case, we
                 // don't need to assign one.
                 pindex->nSequenceId = nBlockSequenceId++;
             }
 
             if (chainActive.Tip() == nullptr ||
                 !setBlockIndexCandidates.value_comp()(pindex,
                                                       chainActive.Tip())) {
                 setBlockIndexCandidates.insert(pindex);
             }
 
             std::pair<std::multimap<CBlockIndex *, CBlockIndex *>::iterator,
                       std::multimap<CBlockIndex *, CBlockIndex *>::iterator>
                 range = mapBlocksUnlinked.equal_range(pindex);
             while (range.first != range.second) {
                 std::multimap<CBlockIndex *, CBlockIndex *>::iterator it =
                     range.first;
                 queue.push_back(it->second);
                 range.first++;
                 mapBlocksUnlinked.erase(it);
             }
         }
     } else if (pindexNew->pprev &&
                pindexNew->pprev->IsValid(BlockValidity::TREE)) {
         mapBlocksUnlinked.insert(std::make_pair(pindexNew->pprev, pindexNew));
     }
 }
 
 static bool FindBlockPos(FlatFilePos &pos, unsigned int nAddSize,
                          unsigned int nHeight, uint64_t nTime,
                          bool fKnown = false) {
     LOCK(cs_LastBlockFile);
 
     unsigned int nFile = fKnown ? pos.nFile : nLastBlockFile;
     if (vinfoBlockFile.size() <= nFile) {
         vinfoBlockFile.resize(nFile + 1);
     }
 
     if (!fKnown) {
         while (vinfoBlockFile[nFile].nSize + nAddSize >= MAX_BLOCKFILE_SIZE) {
             nFile++;
             if (vinfoBlockFile.size() <= nFile) {
                 vinfoBlockFile.resize(nFile + 1);
             }
         }
         pos.nFile = nFile;
         pos.nPos = vinfoBlockFile[nFile].nSize;
     }
 
     if ((int)nFile != nLastBlockFile) {
         if (!fKnown) {
             LogPrintf("Leaving block file %i: %s\n", nLastBlockFile,
                       vinfoBlockFile[nLastBlockFile].ToString());
         }
         FlushBlockFile(!fKnown);
         nLastBlockFile = nFile;
     }
 
     vinfoBlockFile[nFile].AddBlock(nHeight, nTime);
     if (fKnown) {
         vinfoBlockFile[nFile].nSize =
             std::max(pos.nPos + nAddSize, vinfoBlockFile[nFile].nSize);
     } else {
         vinfoBlockFile[nFile].nSize += nAddSize;
     }
 
     if (!fKnown) {
         bool out_of_space;
         size_t bytes_allocated =
             BlockFileSeq().Allocate(pos, nAddSize, out_of_space);
         if (out_of_space) {
             return AbortNode("Disk space is low!",
                              _("Error: Disk space is low!"));
         }
         if (bytes_allocated != 0 && fPruneMode) {
             fCheckForPruning = true;
         }
     }
 
     setDirtyFileInfo.insert(nFile);
     return true;
 }
 
 static bool FindUndoPos(CValidationState &state, int nFile, FlatFilePos &pos,
                         unsigned int nAddSize) {
     pos.nFile = nFile;
 
     LOCK(cs_LastBlockFile);
 
     pos.nPos = vinfoBlockFile[nFile].nUndoSize;
     vinfoBlockFile[nFile].nUndoSize += nAddSize;
     setDirtyFileInfo.insert(nFile);
 
     bool out_of_space;
     size_t bytes_allocated =
         UndoFileSeq().Allocate(pos, nAddSize, out_of_space);
     if (out_of_space) {
         return AbortNode(state, "Disk space is low!",
                          _("Error: Disk space is low!"));
     }
     if (bytes_allocated != 0 && fPruneMode) {
         fCheckForPruning = true;
     }
 
     return true;
 }
 
 /**
  * Return true if the provided block header is valid.
  * Only verify PoW if blockValidationOptions is configured to do so.
  * This allows validation of headers on which the PoW hasn't been done.
  * For example: to validate template handed to mining software.
  * Do not call this for any check that depends on the context.
  * For context-dependent calls, see ContextualCheckBlockHeader.
  */
 static bool CheckBlockHeader(const CBlockHeader &block, CValidationState &state,
                              const Consensus::Params &params,
                              BlockValidationOptions validationOptions) {
     // Check proof of work matches claimed amount
     if (validationOptions.shouldValidatePoW() &&
         !CheckProofOfWork(block.GetHash(), block.nBits, params)) {
         return state.DoS(50, false, REJECT_INVALID, "high-hash", false,
                          "proof of work failed");
     }
 
     return true;
 }
 
 bool CheckBlock(const CBlock &block, CValidationState &state,
                 const Consensus::Params &params,
                 BlockValidationOptions validationOptions) {
     // These are checks that are independent of context.
     if (block.fChecked) {
         return true;
     }
 
     // Check that the header is valid (particularly PoW).  This is mostly
     // redundant with the call in AcceptBlockHeader.
     if (!CheckBlockHeader(block, state, params, validationOptions)) {
         return false;
     }
 
     // Check the merkle root.
     if (validationOptions.shouldValidateMerkleRoot()) {
         bool mutated;
         uint256 hashMerkleRoot2 = BlockMerkleRoot(block, &mutated);
         if (block.hashMerkleRoot != hashMerkleRoot2) {
             return state.DoS(100, false, REJECT_INVALID, "bad-txnmrklroot",
                              true, "hashMerkleRoot mismatch");
         }
 
         // Check for merkle tree malleability (CVE-2012-2459): repeating
         // sequences of transactions in a block without affecting the merkle
         // root of a block, while still invalidating it.
         if (mutated) {
             return state.DoS(100, false, REJECT_INVALID, "bad-txns-duplicate",
                              true, "duplicate transaction");
         }
     }
 
     // All potential-corruption validation must be done before we do any
     // transaction validation, as otherwise we may mark the header as invalid
     // because we receive the wrong transactions for it.
 
     // First transaction must be coinbase.
     if (block.vtx.empty()) {
         return state.DoS(100, false, REJECT_INVALID, "bad-cb-missing", false,
                          "first tx is not coinbase");
     }
 
     // Size limits.
     auto nMaxBlockSize = validationOptions.getExcessiveBlockSize();
 
     // Bail early if there is no way this block is of reasonable size.
     if ((block.vtx.size() * MIN_TRANSACTION_SIZE) > nMaxBlockSize) {
         return state.DoS(100, false, REJECT_INVALID, "bad-blk-length", false,
                          "size limits failed");
     }
 
     auto currentBlockSize = ::GetSerializeSize(block, PROTOCOL_VERSION);
     if (currentBlockSize > nMaxBlockSize) {
         return state.DoS(100, false, REJECT_INVALID, "bad-blk-length", false,
                          "size limits failed");
     }
 
     // And a valid coinbase.
     if (!CheckCoinbase(*block.vtx[0], state)) {
         return state.Invalid(false, state.GetRejectCode(),
                              state.GetRejectReason(),
                              strprintf("Coinbase check failed (txid %s) %s",
                                        block.vtx[0]->GetId().ToString(),
                                        state.GetDebugMessage()));
     }
 
     // Check transactions for regularity, skipping the first. Note that this
     // is the first time we check that all after the first are !IsCoinBase.
     for (size_t i = 1; i < block.vtx.size(); i++) {
         auto *tx = block.vtx[i].get();
         if (!CheckRegularTransaction(*tx, state)) {
             return state.Invalid(
                 false, state.GetRejectCode(), state.GetRejectReason(),
                 strprintf("Transaction check failed (txid %s) %s",
                           tx->GetId().ToString(), state.GetDebugMessage()));
         }
     }
 
     if (validationOptions.shouldValidatePoW() &&
         validationOptions.shouldValidateMerkleRoot()) {
         block.fChecked = true;
     }
 
     return true;
 }
 
 /**
  * Context-dependent validity checks.
  * By "context", we mean only the previous block headers, but not the UTXO
  * set; UTXO-related validity checks are done in ConnectBlock().
  * NOTE: This function is not currently invoked by ConnectBlock(), so we
  * should consider upgrade issues if we change which consensus rules are
  * enforced in this function (eg by adding a new consensus rule). See comment
  * in ConnectBlock().
  * Note that -reindex-chainstate skips the validation that happens here!
  */
 static bool ContextualCheckBlockHeader(const CChainParams &params,
                                        const CBlockHeader &block,
                                        CValidationState &state,
                                        const CBlockIndex *pindexPrev,
                                        int64_t nAdjustedTime) {
     assert(pindexPrev != nullptr);
     const int nHeight = pindexPrev->nHeight + 1;
 
     // Check proof of work
     const Consensus::Params &consensusParams = params.GetConsensus();
     if (block.nBits !=
         GetNextWorkRequired(pindexPrev, &block, consensusParams)) {
         LogPrintf("bad bits after height: %d\n", pindexPrev->nHeight);
         return state.DoS(100, false, REJECT_INVALID, "bad-diffbits", false,
                          "incorrect proof of work");
     }
 
     // Check against checkpoints
     if (fCheckpointsEnabled) {
         const CCheckpointData &checkpoints = params.Checkpoints();
 
         // Check that the block chain matches the known block chain up to a
         // checkpoint.
         if (!Checkpoints::CheckBlock(checkpoints, nHeight, block.GetHash())) {
             return state.DoS(100,
                              error("%s: rejected by checkpoint lock-in at %d",
                                    __func__, nHeight),
                              REJECT_CHECKPOINT, "checkpoint mismatch");
         }
 
         // Don't accept any forks from the main chain prior to last checkpoint.
         // GetLastCheckpoint finds the last checkpoint in MapCheckpoints that's
         // in our MapBlockIndex.
         CBlockIndex *pcheckpoint = Checkpoints::GetLastCheckpoint(checkpoints);
         if (pcheckpoint && nHeight < pcheckpoint->nHeight) {
             return state.DoS(
                 100,
                 error("%s: forked chain older than last checkpoint (height %d)",
                       __func__, nHeight),
                 REJECT_CHECKPOINT, "bad-fork-prior-to-checkpoint");
         }
     }
 
     // Check timestamp against prev
     if (block.GetBlockTime() <= pindexPrev->GetMedianTimePast()) {
         return state.Invalid(false, REJECT_INVALID, "time-too-old",
                              "block's timestamp is too early");
     }
 
     // Check timestamp
     if (block.GetBlockTime() > nAdjustedTime + MAX_FUTURE_BLOCK_TIME) {
         return state.Invalid(false, REJECT_INVALID, "time-too-new",
                              "block timestamp too far in the future");
     }
 
     // Reject outdated version blocks when 95% (75% on testnet) of the network
     // has upgraded:
     // check for version 2, 3 and 4 upgrades
     if ((block.nVersion < 2 && nHeight >= consensusParams.BIP34Height) ||
         (block.nVersion < 3 && nHeight >= consensusParams.BIP66Height) ||
         (block.nVersion < 4 && nHeight >= consensusParams.BIP65Height)) {
         return state.Invalid(
             false, REJECT_OBSOLETE,
             strprintf("bad-version(0x%08x)", block.nVersion),
             strprintf("rejected nVersion=0x%08x block", block.nVersion));
     }
 
     return true;
 }
 
 bool ContextualCheckTransactionForCurrentBlock(const Consensus::Params &params,
                                                const CTransaction &tx,
                                                CValidationState &state,
                                                int flags) {
     AssertLockHeld(cs_main);
 
     // By convention a negative value for flags indicates that the current
     // network-enforced consensus rules should be used. In a future soft-fork
     // scenario that would mean checking which rules would be enforced for the
     // next block and setting the appropriate flags. At the present time no
     // soft-forks are scheduled, so no flags are set.
     flags = std::max(flags, 0);
 
     // ContextualCheckTransactionForCurrentBlock() uses chainActive.Height()+1
     // to evaluate nLockTime because when IsFinalTx() is called within
     // CBlock::AcceptBlock(), the height of the block *being* evaluated is what
     // is used. Thus if we want to know if a transaction can be part of the
     // *next* block, we need to call ContextualCheckTransaction() with one more
     // than chainActive.Height().
     const int nBlockHeight = chainActive.Height() + 1;
 
     // BIP113 will require that time-locked transactions have nLockTime set to
     // less than the median time of the previous block they're contained in.
     // When the next block is created its previous block will be the current
     // chain tip, so we use that to calculate the median time passed to
     // ContextualCheckTransaction() if LOCKTIME_MEDIAN_TIME_PAST is set.
     const int64_t nMedianTimePast =
         chainActive.Tip() == nullptr ? 0
                                      : chainActive.Tip()->GetMedianTimePast();
     const int64_t nLockTimeCutoff = (flags & LOCKTIME_MEDIAN_TIME_PAST)
                                         ? nMedianTimePast
                                         : GetAdjustedTime();
 
     return ContextualCheckTransaction(params, tx, state, nBlockHeight,
                                       nLockTimeCutoff, nMedianTimePast);
 }
 
 /**
  * NOTE: This function is not currently invoked by ConnectBlock(), so we
  * should consider upgrade issues if we change which consensus rules are
  * enforced in this function (eg by adding a new consensus rule). See comment
  * in ConnectBlock().
  * Note that -reindex-chainstate skips the validation that happens here!
  */
 static bool ContextualCheckBlock(const CBlock &block, CValidationState &state,
                                  const Consensus::Params &params,
                                  const CBlockIndex *pindexPrev) {
     const int nHeight = pindexPrev == nullptr ? 0 : pindexPrev->nHeight + 1;
 
     // Start enforcing BIP113 (Median Time Past).
     int nLockTimeFlags = 0;
     if (nHeight >= params.CSVHeight) {
         assert(pindexPrev != nullptr);
         nLockTimeFlags |= LOCKTIME_MEDIAN_TIME_PAST;
     }
 
     const int64_t nMedianTimePast =
         pindexPrev == nullptr ? 0 : pindexPrev->GetMedianTimePast();
 
     const int64_t nLockTimeCutoff = (nLockTimeFlags & LOCKTIME_MEDIAN_TIME_PAST)
                                         ? nMedianTimePast
                                         : block.GetBlockTime();
 
     const bool fIsMagneticAnomalyEnabled =
         IsMagneticAnomalyEnabled(params, pindexPrev);
 
     // Keep track of the sigops count.
     uint64_t nSigOps = 0;
     const auto currentBlockSize = ::GetSerializeSize(block, PROTOCOL_VERSION);
     auto nMaxSigOpsCount = GetMaxBlockSigOpsCount(currentBlockSize);
     // Note that pindexPrev may be null if reindexing genesis block.
     const auto scriptFlags = pindexPrev
                                  ? GetNextBlockScriptFlags(params, pindexPrev)
                                  : SCRIPT_VERIFY_NONE;
 
     // Check transactions:
     // - canonical ordering
     // - ensure they are finalized
     // - perform a preliminary block-sigops count (they will be recounted more
     // strictly during ConnectBlock).
     // - perform a transaction-sigops check (again, a more strict check will
     // happen in ConnectBlock).
     const CTransaction *prevTx = nullptr;
     for (const auto &ptx : block.vtx) {
         const CTransaction &tx = *ptx;
         if (fIsMagneticAnomalyEnabled) {
             if (prevTx && (tx.GetId() <= prevTx->GetId())) {
                 if (tx.GetId() == prevTx->GetId()) {
                     return state.DoS(100, false, REJECT_INVALID, "tx-duplicate",
                                      false,
                                      strprintf("Duplicated transaction %s",
                                                tx.GetId().ToString()));
                 }
 
                 return state.DoS(
                     100, false, REJECT_INVALID, "tx-ordering", false,
                     strprintf("Transaction order is invalid (%s < %s)",
                               tx.GetId().ToString(),
                               prevTx->GetId().ToString()));
             }
 
             if (prevTx || !tx.IsCoinBase()) {
                 prevTx = &tx;
             }
         }
 
         // Count the sigops for the current transaction. If the tx or total
         // sigops counts are too high, then the block is invalid.
         const auto txSigOps = GetSigOpCountWithoutP2SH(tx, scriptFlags);
         if (txSigOps > MAX_TX_SIGOPS_COUNT) {
             return state.DoS(100, false, REJECT_INVALID, "bad-txn-sigops",
                              false, "out-of-bounds SigOpCount");
         }
         nSigOps += txSigOps;
         if (nSigOps > nMaxSigOpsCount) {
             return state.DoS(100, false, REJECT_INVALID, "bad-blk-sigops",
                              false, "out-of-bounds SigOpCount");
         }
 
         if (!ContextualCheckTransaction(params, tx, state, nHeight,
                                         nLockTimeCutoff, nMedianTimePast)) {
             // state set by ContextualCheckTransaction.
             return false;
         }
     }
 
     // Enforce rule that the coinbase starts with serialized block height
     if (nHeight >= params.BIP34Height) {
         CScript expect = CScript() << nHeight;
         if (block.vtx[0]->vin[0].scriptSig.size() < expect.size() ||
             !std::equal(expect.begin(), expect.end(),
                         block.vtx[0]->vin[0].scriptSig.begin())) {
             return state.DoS(100, false, REJECT_INVALID, "bad-cb-height", false,
                              "block height mismatch in coinbase");
         }
     }
 
     return true;
 }
 
 /**
  * If the provided block header is valid, add it to the block index.
  *
  * Returns true if the block is successfully added to the block index.
  */
 bool CChainState::AcceptBlockHeader(const Config &config,
                                     const CBlockHeader &block,
                                     CValidationState &state,
                                     CBlockIndex **ppindex) {
     AssertLockHeld(cs_main);
     const CChainParams &chainparams = config.GetChainParams();
 
     // Check for duplicate
     BlockHash hash = block.GetHash();
     BlockMap::iterator miSelf = mapBlockIndex.find(hash);
     CBlockIndex *pindex = nullptr;
     if (hash != chainparams.GetConsensus().hashGenesisBlock) {
         if (miSelf != mapBlockIndex.end()) {
             // Block header is already known.
             pindex = miSelf->second;
             if (ppindex) {
                 *ppindex = pindex;
             }
 
             if (pindex->nStatus.isInvalid()) {
                 return state.Invalid(error("%s: block %s is marked invalid",
                                            __func__, hash.ToString()),
                                      0, "duplicate");
             }
 
             return true;
         }
 
         if (!CheckBlockHeader(block, state, chainparams.GetConsensus(),
                               BlockValidationOptions(config))) {
             return error("%s: Consensus::CheckBlockHeader: %s, %s", __func__,
                          hash.ToString(), FormatStateMessage(state));
         }
 
         // Get prev block index
         BlockMap::iterator mi = mapBlockIndex.find(block.hashPrevBlock);
         if (mi == mapBlockIndex.end()) {
             return state.DoS(10, error("%s: prev block not found", __func__), 0,
                              "prev-blk-not-found");
         }
 
         CBlockIndex *pindexPrev = (*mi).second;
         assert(pindexPrev);
         if (pindexPrev->nStatus.isInvalid()) {
             return state.DoS(100, error("%s: prev block invalid", __func__),
                              REJECT_INVALID, "bad-prevblk");
         }
 
         if (!ContextualCheckBlockHeader(chainparams, block, state, pindexPrev,
                                         GetAdjustedTime())) {
             return error("%s: Consensus::ContextualCheckBlockHeader: %s, %s",
                          __func__, hash.ToString(), FormatStateMessage(state));
         }
 
         /* Determine if this block descends from any block which has been found
          * invalid (m_failed_blocks), then mark pindexPrev and any blocks
          * between them as failed. For example:
          *
          *                D3
          *              /
          *      B2 - C2
          *    /         \
          *  A             D2 - E2 - F2
          *    \
          *      B1 - C1 - D1 - E1
          *
          * In the case that we attempted to reorg from E1 to F2, only to find
          * C2 to be invalid, we would mark D2, E2, and F2 as BLOCK_FAILED_CHILD
          * but NOT D3 (it was not in any of our candidate sets at the time).
          *
          * In any case D3 will also be marked as BLOCK_FAILED_CHILD at restart
          * in LoadBlockIndex.
          */
         if (!pindexPrev->IsValid(BlockValidity::SCRIPTS)) {
             // The above does not mean "invalid": it checks if the previous
             // block hasn't been validated up to BLOCK_VALID_SCRIPTS. This is a
             // performance optimization, in the common case of adding a new
             // block to the tip, we don't need to iterate over the failed blocks
             // list.
             for (const CBlockIndex *failedit : m_failed_blocks) {
                 if (pindexPrev->GetAncestor(failedit->nHeight) == failedit) {
                     assert(failedit->nStatus.hasFailed());
                     CBlockIndex *invalid_walk = pindexPrev;
                     while (invalid_walk != failedit) {
                         invalid_walk->nStatus =
                             invalid_walk->nStatus.withFailedParent();
                         setDirtyBlockIndex.insert(invalid_walk);
                         invalid_walk = invalid_walk->pprev;
                     }
                     return state.DoS(100,
                                      error("%s: prev block invalid", __func__),
                                      REJECT_INVALID, "bad-prevblk");
                 }
             }
         }
     }
 
     if (pindex == nullptr) {
         pindex = AddToBlockIndex(block);
     }
 
     if (ppindex) {
         *ppindex = pindex;
     }
 
     CheckBlockIndex(chainparams.GetConsensus());
     return true;
 }
 
 // Exposed wrapper for AcceptBlockHeader
 bool ProcessNewBlockHeaders(const Config &config,
                             const std::vector<CBlockHeader> &headers,
                             CValidationState &state,
                             const CBlockIndex **ppindex,
                             CBlockHeader *first_invalid) {
     if (first_invalid != nullptr) {
         first_invalid->SetNull();
     }
 
     {
         LOCK(cs_main);
         for (const CBlockHeader &header : headers) {
             // Use a temp pindex instead of ppindex to avoid a const_cast
             CBlockIndex *pindex = nullptr;
             if (!g_chainstate.AcceptBlockHeader(config, header, state,
                                                 &pindex)) {
                 if (first_invalid) {
                     *first_invalid = header;
                 }
                 return false;
             }
 
             if (ppindex) {
                 *ppindex = pindex;
             }
         }
     }
 
     NotifyHeaderTip();
     return true;
 }
 
 /**
  * Store block on disk. If dbp is non-nullptr, the file is known to already
  * reside on disk.
  */
 static FlatFilePos SaveBlockToDisk(const CBlock &block, int nHeight,
                                    const CChainParams &chainparams,
                                    const FlatFilePos *dbp) {
     unsigned int nBlockSize = ::GetSerializeSize(block, CLIENT_VERSION);
     FlatFilePos blockPos;
     if (dbp != nullptr) {
         blockPos = *dbp;
     }
     if (!FindBlockPos(blockPos, nBlockSize + 8, nHeight, block.GetBlockTime(),
                       dbp != nullptr)) {
         error("%s: FindBlockPos failed", __func__);
         return FlatFilePos();
     }
     if (dbp == nullptr) {
         if (!WriteBlockToDisk(block, blockPos, chainparams.DiskMagic())) {
             AbortNode("Failed to write block");
             return FlatFilePos();
         }
     }
     return blockPos;
 }
 
 /**
  * Store a block on disk.
  *
  * @param[in]     config     The global config.
  * @param[in-out] pblock     The block we want to accept.
  * @param[in]     fRequested A boolean to indicate if this block was requested
  *                           from our peers.
  * @param[in]     dbp        If non-null, the disk position of the block.
  * @param[in-out] fNewBlock  True if block was first received via this call.
  * @return True if the block is accepted as a valid block and written to disk.
  */
 bool CChainState::AcceptBlock(const Config &config,
                               const std::shared_ptr<const CBlock> &pblock,
                               CValidationState &state, bool fRequested,
                               const FlatFilePos *dbp, bool *fNewBlock) {
     AssertLockHeld(cs_main);
 
     const CBlock &block = *pblock;
     if (fNewBlock) {
         *fNewBlock = false;
     }
 
     CBlockIndex *pindex = nullptr;
     if (!AcceptBlockHeader(config, block, state, &pindex)) {
         return false;
     }
 
     // Try to process all requested blocks that we don't have, but only
     // process an unrequested block if it's new and has enough work to
     // advance our tip, and isn't too many blocks ahead.
     bool fAlreadyHave = pindex->nStatus.hasData();
 
     // TODO: deal better with return value and error conditions for duplicate
     // and unrequested blocks.
     if (fAlreadyHave) {
         return true;
     }
 
     // Compare block header timestamps and received times of the block and the
     // chaintip.  If they have the same chain height, use these diffs as a
     // tie-breaker, attempting to pick the more honestly-mined block.
     int64_t newBlockTimeDiff = std::llabs(pindex->GetReceivedTimeDiff());
     int64_t chainTipTimeDiff =
         chainActive.Tip() ? std::llabs(chainActive.Tip()->GetReceivedTimeDiff())
                           : 0;
 
     bool isSameHeight = chainActive.Tip() &&
                         (pindex->nChainWork == chainActive.Tip()->nChainWork);
     if (isSameHeight) {
         LogPrintf("Chain tip timestamp-to-received-time difference: hash=%s, "
                   "diff=%d\n",
                   chainActive.Tip()->GetBlockHash().ToString(),
                   chainTipTimeDiff);
         LogPrintf("New block timestamp-to-received-time difference: hash=%s, "
                   "diff=%d\n",
                   pindex->GetBlockHash().ToString(), newBlockTimeDiff);
     }
 
     bool fHasMoreOrSameWork =
         (chainActive.Tip() ? pindex->nChainWork >= chainActive.Tip()->nChainWork
                            : true);
 
     // Blocks that are too out-of-order needlessly limit the effectiveness of
     // pruning, because pruning will not delete block files that contain any
     // blocks which are too close in height to the tip.  Apply this test
     // regardless of whether pruning is enabled; it should generally be safe to
     // not process unrequested blocks.
     bool fTooFarAhead =
         (pindex->nHeight > int(chainActive.Height() + MIN_BLOCKS_TO_KEEP));
 
     // TODO: Decouple this function from the block download logic by removing
     // fRequested
     // This requires some new chain data structure to efficiently look up if a
     // block is in a chain leading to a candidate for best tip, despite not
     // being such a candidate itself.
 
     // If we didn't ask for it:
     if (!fRequested) {
         // This is a previously-processed block that was pruned.
         if (pindex->nTx != 0) {
             return true;
         }
 
         // Don't process less-work chains.
         if (!fHasMoreOrSameWork) {
             return true;
         }
 
         // Block height is too high.
         if (fTooFarAhead) {
             return true;
         }
 
         // Protect against DoS attacks from low-work chains.
         // If our tip is behind, a peer could try to send us
         // low-work blocks on a fake chain that we would never
         // request; don't process these.
         if (pindex->nChainWork < nMinimumChainWork) {
             return true;
         }
     }
 
     const CChainParams &chainparams = config.GetChainParams();
     const Consensus::Params &consensusParams = chainparams.GetConsensus();
 
     if (!CheckBlock(block, state, consensusParams,
                     BlockValidationOptions(config)) ||
         !ContextualCheckBlock(block, state, consensusParams, pindex->pprev)) {
         if (state.IsInvalid() && !state.CorruptionPossible()) {
             pindex->nStatus = pindex->nStatus.withFailed();
             setDirtyBlockIndex.insert(pindex);
         }
 
         return error("%s: %s (block %s)", __func__, FormatStateMessage(state),
                      block.GetHash().ToString());
     }
 
     // If this is a deep reorg (a regorg of more than one block), preemptively
     // mark the chain as parked. If it has enough work, it'll unpark
     // automatically. We mark the block as parked at the very last minute so we
     // can make sure everything is ready to be reorged if needed.
     if (gArgs.GetBoolArg("-parkdeepreorg", true)) {
         const CBlockIndex *pindexFork = chainActive.FindFork(pindex);
         if (pindexFork && pindexFork->nHeight + 1 < pindex->nHeight) {
             LogPrintf("Park block %s as it would cause a deep reorg.\n",
                       pindex->GetBlockHash().ToString());
             pindex->nStatus = pindex->nStatus.withParked();
             setDirtyBlockIndex.insert(pindex);
         }
     }
 
     // Header is valid/has work and the merkle tree is good.
     // Relay now, but if it does not build on our best tip, let the
     // SendMessages loop relay it.
     if (!IsInitialBlockDownload() && chainActive.Tip() == pindex->pprev) {
         GetMainSignals().NewPoWValidBlock(pindex, pblock);
     }
 
     // Write block to history file
     if (fNewBlock) {
         *fNewBlock = true;
     }
     try {
         FlatFilePos blockPos =
             SaveBlockToDisk(block, pindex->nHeight, chainparams, dbp);
         if (blockPos.IsNull()) {
             state.Error(strprintf(
                 "%s: Failed to find position to write new block to disk",
                 __func__));
             return false;
         }
         ReceivedBlockTransactions(block, pindex, blockPos);
     } catch (const std::runtime_error &e) {
         return AbortNode(state, std::string("System error: ") + e.what());
     }
 
     FlushStateToDisk(chainparams, state, FlushStateMode::NONE);
 
     CheckBlockIndex(consensusParams);
 
     return true;
 }
 
 bool ProcessNewBlock(const Config &config,
                      const std::shared_ptr<const CBlock> pblock,
                      bool fForceProcessing, bool *fNewBlock) {
     AssertLockNotHeld(cs_main);
 
     {
         if (fNewBlock) {
             *fNewBlock = false;
         }
 
         CValidationState state;
 
         // CheckBlock() does not support multi-threaded block validation
         // because CBlock::fChecked can cause data race.
         // Therefore, the following critical section must include the
         // CheckBlock() call as well.
         LOCK(cs_main);
 
         // Ensure that CheckBlock() passes before calling AcceptBlock, as
         // belt-and-suspenders.
         bool ret =
             CheckBlock(*pblock, state, config.GetChainParams().GetConsensus(),
                        BlockValidationOptions(config));
         if (ret) {
             // Store to disk
             ret = g_chainstate.AcceptBlock(
                 config, pblock, state, fForceProcessing, nullptr, fNewBlock);
         }
 
         if (!ret) {
             GetMainSignals().BlockChecked(*pblock, state);
             return error("%s: AcceptBlock FAILED (%s)", __func__,
                          FormatStateMessage(state));
         }
     }
 
     NotifyHeaderTip();
 
     // Only used to report errors, not invalidity - ignore it
     CValidationState state;
     if (!g_chainstate.ActivateBestChain(config, state, pblock)) {
         return error("%s: ActivateBestChain failed (%s)", __func__,
                      FormatStateMessage(state));
     }
 
     return true;
 }
 
 bool TestBlockValidity(CValidationState &state, const CChainParams &params,
                        const CBlock &block, CBlockIndex *pindexPrev,
                        BlockValidationOptions validationOptions) {
     AssertLockHeld(cs_main);
     assert(pindexPrev && pindexPrev == chainActive.Tip());
     CCoinsViewCache viewNew(pcoinsTip.get());
     BlockHash block_hash(block.GetHash());
     CBlockIndex indexDummy(block);
     indexDummy.pprev = pindexPrev;
     indexDummy.nHeight = pindexPrev->nHeight + 1;
     indexDummy.phashBlock = &block_hash;
 
     // NOTE: CheckBlockHeader is called by CheckBlock
     if (!ContextualCheckBlockHeader(params, block, state, pindexPrev,
                                     GetAdjustedTime())) {
         return error("%s: Consensus::ContextualCheckBlockHeader: %s", __func__,
                      FormatStateMessage(state));
     }
 
     if (!CheckBlock(block, state, params.GetConsensus(), validationOptions)) {
         return error("%s: Consensus::CheckBlock: %s", __func__,
                      FormatStateMessage(state));
     }
 
     if (!ContextualCheckBlock(block, state, params.GetConsensus(),
                               pindexPrev)) {
         return error("%s: Consensus::ContextualCheckBlock: %s", __func__,
                      FormatStateMessage(state));
     }
 
     if (!g_chainstate.ConnectBlock(block, state, &indexDummy, viewNew, params,
                                    validationOptions, true)) {
         return false;
     }
 
     assert(state.IsValid());
     return true;
 }
 
 /**
  * BLOCK PRUNING CODE
  */
 
 /**
  * Calculate the amount of disk space the block & undo files currently use.
  */
 uint64_t CalculateCurrentUsage() {
     LOCK(cs_LastBlockFile);
 
     uint64_t retval = 0;
     for (const CBlockFileInfo &file : vinfoBlockFile) {
         retval += file.nSize + file.nUndoSize;
     }
 
     return retval;
 }
 
 /**
  * Prune a block file (modify associated database entries)
  */
 void PruneOneBlockFile(const int fileNumber) {
     LOCK(cs_LastBlockFile);
 
     for (const auto &entry : mapBlockIndex) {
         CBlockIndex *pindex = entry.second;
         if (pindex->nFile == fileNumber) {
             pindex->nStatus = pindex->nStatus.withData(false).withUndo(false);
             pindex->nFile = 0;
             pindex->nDataPos = 0;
             pindex->nUndoPos = 0;
             setDirtyBlockIndex.insert(pindex);
 
             // Prune from mapBlocksUnlinked -- any block we prune would have
             // to be downloaded again in order to consider its chain, at which
             // point it would be considered as a candidate for
             // mapBlocksUnlinked or setBlockIndexCandidates.
             std::pair<std::multimap<CBlockIndex *, CBlockIndex *>::iterator,
                       std::multimap<CBlockIndex *, CBlockIndex *>::iterator>
                 range = mapBlocksUnlinked.equal_range(pindex->pprev);
             while (range.first != range.second) {
                 std::multimap<CBlockIndex *, CBlockIndex *>::iterator _it =
                     range.first;
                 range.first++;
                 if (_it->second == pindex) {
                     mapBlocksUnlinked.erase(_it);
                 }
             }
         }
     }
 
     vinfoBlockFile[fileNumber].SetNull();
     setDirtyFileInfo.insert(fileNumber);
 }
 
 void UnlinkPrunedFiles(const std::set<int> &setFilesToPrune) {
     for (const int i : setFilesToPrune) {
         FlatFilePos pos(i, 0);
         fs::remove(BlockFileSeq().FileName(pos));
         fs::remove(UndoFileSeq().FileName(pos));
         LogPrintf("Prune: %s deleted blk/rev (%05u)\n", __func__, i);
     }
 }
 
 /**
  * Calculate the block/rev files to delete based on height specified by user
  * with RPC command pruneblockchain
  */
 static void FindFilesToPruneManual(std::set<int> &setFilesToPrune,
                                    int nManualPruneHeight) {
     assert(fPruneMode && nManualPruneHeight > 0);
 
     LOCK2(cs_main, cs_LastBlockFile);
     if (chainActive.Tip() == nullptr) {
         return;
     }
 
     // last block to prune is the lesser of (user-specified height,
     // MIN_BLOCKS_TO_KEEP from the tip)
     unsigned int nLastBlockWeCanPrune =
         std::min((unsigned)nManualPruneHeight,
                  chainActive.Tip()->nHeight - MIN_BLOCKS_TO_KEEP);
     int count = 0;
     for (int fileNumber = 0; fileNumber < nLastBlockFile; fileNumber++) {
         if (vinfoBlockFile[fileNumber].nSize == 0 ||
             vinfoBlockFile[fileNumber].nHeightLast > nLastBlockWeCanPrune) {
             continue;
         }
         PruneOneBlockFile(fileNumber);
         setFilesToPrune.insert(fileNumber);
         count++;
     }
     LogPrintf("Prune (Manual): prune_height=%d removed %d blk/rev pairs\n",
               nLastBlockWeCanPrune, count);
 }
 
 /* This function is called from the RPC code for pruneblockchain */
 void PruneBlockFilesManual(int nManualPruneHeight) {
     CValidationState state;
     const CChainParams &chainparams = Params();
     if (!FlushStateToDisk(chainparams, state, FlushStateMode::NONE,
                           nManualPruneHeight)) {
         LogPrintf("%s: failed to flush state (%s)\n", __func__,
                   FormatStateMessage(state));
     }
 }
 
 /**
  * Prune block and undo files (blk???.dat and undo???.dat) so that the disk
  * space used is less than a user-defined target. The user sets the target (in
  * MB) on the command line or in config file.  This will be run on startup and
  * whenever new space is allocated in a block or undo file, staying below the
  * target. Changing back to unpruned requires a reindex (which in this case
  * means the blockchain must be re-downloaded.)
  *
  * Pruning functions are called from FlushStateToDisk when the global
  * fCheckForPruning flag has been set. Block and undo files are deleted in
  * lock-step (when blk00003.dat is deleted, so is rev00003.dat.). Pruning cannot
  * take place until the longest chain is at least a certain length (100000 on
  * mainnet, 1000 on testnet, 1000 on regtest). Pruning will never delete a block
  * within a defined distance (currently 288) from the active chain's tip. The
  * block index is updated by unsetting HAVE_DATA and HAVE_UNDO for any blocks
  * that were stored in the deleted files. A db flag records the fact that at
  * least some block files have been pruned.
  *
  * @param[out]   setFilesToPrune   The set of file indices that can be unlinked
  * will be returned
  */
 static void FindFilesToPrune(std::set<int> &setFilesToPrune,
                              uint64_t nPruneAfterHeight) {
     LOCK2(cs_main, cs_LastBlockFile);
     if (chainActive.Tip() == nullptr || nPruneTarget == 0) {
         return;
     }
     if (uint64_t(chainActive.Tip()->nHeight) <= nPruneAfterHeight) {
         return;
     }
 
     unsigned int nLastBlockWeCanPrune =
         chainActive.Tip()->nHeight - MIN_BLOCKS_TO_KEEP;
     uint64_t nCurrentUsage = CalculateCurrentUsage();
     // We don't check to prune until after we've allocated new space for files,
     // so we should leave a buffer under our target to account for another
     // allocation before the next pruning.
     uint64_t nBuffer = BLOCKFILE_CHUNK_SIZE + UNDOFILE_CHUNK_SIZE;
     uint64_t nBytesToPrune;
     int count = 0;
 
     if (nCurrentUsage + nBuffer >= nPruneTarget) {
         // On a prune event, the chainstate DB is flushed.
         // To avoid excessive prune events negating the benefit of high dbcache
         // values, we should not prune too rapidly.
         // So when pruning in IBD, increase the buffer a bit to avoid a re-prune
         // too soon.
         if (IsInitialBlockDownload()) {
             // Since this is only relevant during IBD, we use a fixed 10%
             nBuffer += nPruneTarget / 10;
         }
 
         for (int fileNumber = 0; fileNumber < nLastBlockFile; fileNumber++) {
             nBytesToPrune = vinfoBlockFile[fileNumber].nSize +
                             vinfoBlockFile[fileNumber].nUndoSize;
 
             if (vinfoBlockFile[fileNumber].nSize == 0) {
                 continue;
             }
 
             // are we below our target?
             if (nCurrentUsage + nBuffer < nPruneTarget) {
                 break;
             }
 
             // don't prune files that could have a block within
             // MIN_BLOCKS_TO_KEEP of the main chain's tip but keep scanning
             if (vinfoBlockFile[fileNumber].nHeightLast > nLastBlockWeCanPrune) {
                 continue;
             }
 
             PruneOneBlockFile(fileNumber);
             // Queue up the files for removal
             setFilesToPrune.insert(fileNumber);
             nCurrentUsage -= nBytesToPrune;
             count++;
         }
     }
 
     LogPrint(BCLog::PRUNE,
              "Prune: target=%dMiB actual=%dMiB diff=%dMiB "
              "max_prune_height=%d removed %d blk/rev pairs\n",
              nPruneTarget / 1024 / 1024, nCurrentUsage / 1024 / 1024,
              ((int64_t)nPruneTarget - (int64_t)nCurrentUsage) / 1024 / 1024,
              nLastBlockWeCanPrune, count);
 }
 
 static FlatFileSeq BlockFileSeq() {
     return FlatFileSeq(GetBlocksDir(), "blk", BLOCKFILE_CHUNK_SIZE);
 }
 
 static FlatFileSeq UndoFileSeq() {
     return FlatFileSeq(GetBlocksDir(), "rev", UNDOFILE_CHUNK_SIZE);
 }
 
 FILE *OpenBlockFile(const FlatFilePos &pos, bool fReadOnly) {
     return BlockFileSeq().Open(pos, fReadOnly);
 }
 
 /** Open an undo file (rev?????.dat) */
 static FILE *OpenUndoFile(const FlatFilePos &pos, bool fReadOnly) {
     return UndoFileSeq().Open(pos, fReadOnly);
 }
 
 fs::path GetBlockPosFilename(const FlatFilePos &pos) {
     return BlockFileSeq().FileName(pos);
 }
 
 CBlockIndex *CChainState::InsertBlockIndex(const BlockHash &hash) {
     AssertLockHeld(cs_main);
 
     if (hash.IsNull()) {
         return nullptr;
     }
 
     // Return existing
     BlockMap::iterator mi = mapBlockIndex.find(hash);
     if (mi != mapBlockIndex.end()) {
         return (*mi).second;
     }
 
     // Create new
     CBlockIndex *pindexNew = new CBlockIndex();
     mi = mapBlockIndex.insert(std::make_pair(hash, pindexNew)).first;
     pindexNew->phashBlock = &((*mi).first);
 
     return pindexNew;
 }
 
 bool CChainState::LoadBlockIndex(const Config &config,
                                  CBlockTreeDB &blocktree) {
     AssertLockHeld(cs_main);
     if (!blocktree.LoadBlockIndexGuts(
             config.GetChainParams().GetConsensus(),
             [this](const BlockHash &hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
                 return this->InsertBlockIndex(hash);
             })) {
         return false;
     }
 
     // Calculate nChainWork
     std::vector<std::pair<int, CBlockIndex *>> vSortedByHeight;
     vSortedByHeight.reserve(mapBlockIndex.size());
     for (const std::pair<const BlockHash, CBlockIndex *> &item :
          mapBlockIndex) {
         CBlockIndex *pindex = item.second;
         vSortedByHeight.push_back(std::make_pair(pindex->nHeight, pindex));
     }
 
     sort(vSortedByHeight.begin(), vSortedByHeight.end());
     for (const std::pair<int, CBlockIndex *> &item : vSortedByHeight) {
         CBlockIndex *pindex = item.second;
         pindex->nChainWork = (pindex->pprev ? pindex->pprev->nChainWork : 0) +
                              GetBlockProof(*pindex);
         pindex->nTimeMax =
             (pindex->pprev ? std::max(pindex->pprev->nTimeMax, pindex->nTime)
                            : pindex->nTime);
         // We can link the chain of blocks for which we've received transactions
         // at some point. Pruned nodes may have deleted the block.
         if (pindex->nTx > 0) {
             if (pindex->pprev) {
                 if (pindex->pprev->HaveTxsDownloaded()) {
                     pindex->nChainTx = pindex->pprev->nChainTx + pindex->nTx;
                 } else {
                     pindex->nChainTx = 0;
                     mapBlocksUnlinked.insert(
                         std::make_pair(pindex->pprev, pindex));
                 }
             } else {
                 pindex->nChainTx = pindex->nTx;
             }
         }
 
         if (!pindex->nStatus.hasFailed() && pindex->pprev &&
             pindex->pprev->nStatus.hasFailed()) {
             pindex->nStatus = pindex->nStatus.withFailedParent();
             setDirtyBlockIndex.insert(pindex);
         }
         if (pindex->IsValid(BlockValidity::TRANSACTIONS) &&
             (pindex->HaveTxsDownloaded() || pindex->pprev == nullptr)) {
             setBlockIndexCandidates.insert(pindex);
         }
 
         if (pindex->nStatus.isInvalid() &&
             (!pindexBestInvalid ||
              pindex->nChainWork > pindexBestInvalid->nChainWork)) {
             pindexBestInvalid = pindex;
         }
 
         if (pindex->nStatus.isOnParkedChain() &&
             (!pindexBestParked ||
              pindex->nChainWork > pindexBestParked->nChainWork)) {
             pindexBestParked = pindex;
         }
 
         if (pindex->pprev) {
             pindex->BuildSkip();
         }
 
         if (pindex->IsValid(BlockValidity::TREE) &&
             (pindexBestHeader == nullptr ||
              CBlockIndexWorkComparator()(pindexBestHeader, pindex))) {
             pindexBestHeader = pindex;
         }
     }
 
     return true;
 }
 
 static bool LoadBlockIndexDB(const Config &config)
     EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
     if (!g_chainstate.LoadBlockIndex(config, *pblocktree)) {
         return false;
     }
 
     // Load block file info
     pblocktree->ReadLastBlockFile(nLastBlockFile);
     vinfoBlockFile.resize(nLastBlockFile + 1);
     LogPrintf("%s: last block file = %i\n", __func__, nLastBlockFile);
     for (int nFile = 0; nFile <= nLastBlockFile; nFile++) {
         pblocktree->ReadBlockFileInfo(nFile, vinfoBlockFile[nFile]);
     }
 
     LogPrintf("%s: last block file info: %s\n", __func__,
               vinfoBlockFile[nLastBlockFile].ToString());
 
     for (int nFile = nLastBlockFile + 1; true; nFile++) {
         CBlockFileInfo info;
         if (pblocktree->ReadBlockFileInfo(nFile, info)) {
             vinfoBlockFile.push_back(info);
         } else {
             break;
         }
     }
 
     // Check presence of blk files
     LogPrintf("Checking all blk files are present...\n");
     std::set<int> setBlkDataFiles;
     for (const std::pair<const BlockHash, CBlockIndex *> &item :
          mapBlockIndex) {
         CBlockIndex *pindex = item.second;
         if (pindex->nStatus.hasData()) {
             setBlkDataFiles.insert(pindex->nFile);
         }
     }
 
     for (const int i : setBlkDataFiles) {
         FlatFilePos pos(i, 0);
         if (CAutoFile(OpenBlockFile(pos, true), SER_DISK, CLIENT_VERSION)
                 .IsNull()) {
             return false;
         }
     }
 
     // Check whether we have ever pruned block & undo files
     pblocktree->ReadFlag("prunedblockfiles", fHavePruned);
     if (fHavePruned) {
         LogPrintf(
             "LoadBlockIndexDB(): Block files have previously been pruned\n");
     }
 
     // Check whether we need to continue reindexing
     bool fReindexing = false;
     pblocktree->ReadReindexing(fReindexing);
     if (fReindexing) {
         fReindex = true;
     }
 
     return true;
 }
 
 bool LoadChainTip(const Config &config) {
     AssertLockHeld(cs_main);
 
     if (chainActive.Tip() &&
         chainActive.Tip()->GetBlockHash() == pcoinsTip->GetBestBlock()) {
         return true;
     }
 
     if (pcoinsTip->GetBestBlock().IsNull() && mapBlockIndex.size() == 1) {
         // In case we just added the genesis block, connect it now, so
         // that we always have a chainActive.Tip() when we return.
         LogPrintf("%s: Connecting genesis block...\n", __func__);
         CValidationState state;
         if (!ActivateBestChain(config, state)) {
             LogPrintf("%s: failed to activate chain (%s)\n", __func__,
                       FormatStateMessage(state));
             return false;
         }
     }
 
     // Load pointer to end of best chain
     CBlockIndex *pindex = LookupBlockIndex(pcoinsTip->GetBestBlock());
     if (!pindex) {
         return false;
     }
     chainActive.SetTip(pindex);
 
     g_chainstate.PruneBlockIndexCandidates();
 
     LogPrintf(
         "Loaded best chain: hashBestChain=%s height=%d date=%s progress=%f\n",
         chainActive.Tip()->GetBlockHash().ToString(), chainActive.Height(),
         FormatISO8601DateTime(chainActive.Tip()->GetBlockTime()),
         GuessVerificationProgress(config.GetChainParams().TxData(),
                                   chainActive.Tip()));
     return true;
 }
 
 CVerifyDB::CVerifyDB() {
     uiInterface.ShowProgress(_("Verifying blocks..."), 0, false);
 }
 
 CVerifyDB::~CVerifyDB() {
     uiInterface.ShowProgress("", 100, false);
 }
 
 bool CVerifyDB::VerifyDB(const Config &config, CCoinsView *coinsview,
                          int nCheckLevel, int nCheckDepth) {
     LOCK(cs_main);
 
     const CChainParams &params = config.GetChainParams();
     const Consensus::Params &consensusParams = params.GetConsensus();
 
     if (chainActive.Tip() == nullptr || chainActive.Tip()->pprev == nullptr) {
         return true;
     }
 
     // Verify blocks in the best chain
     if (nCheckDepth <= 0 || nCheckDepth > chainActive.Height()) {
         nCheckDepth = chainActive.Height();
     }
 
     nCheckLevel = std::max(0, std::min(4, nCheckLevel));
     LogPrintf("Verifying last %i blocks at level %i\n", nCheckDepth,
               nCheckLevel);
 
     CCoinsViewCache coins(coinsview);
     CBlockIndex *pindex;
     CBlockIndex *pindexFailure = nullptr;
     int nGoodTransactions = 0;
     CValidationState state;
     int reportDone = 0;
     LogPrintfToBeContinued("[0%%]...");
     for (pindex = chainActive.Tip(); pindex && pindex->pprev;
          pindex = pindex->pprev) {
         boost::this_thread::interruption_point();
         int percentageDone = std::max(
             1, std::min(
                    99,
                    (int)(((double)(chainActive.Height() - pindex->nHeight)) /
                          (double)nCheckDepth * (nCheckLevel >= 4 ? 50 : 100))));
 
         if (reportDone < percentageDone / 10) {
             // report every 10% step
             LogPrintfToBeContinued("[%d%%]...", percentageDone);
             reportDone = percentageDone / 10;
         }
 
         uiInterface.ShowProgress(_("Verifying blocks..."), percentageDone,
                                  false);
         if (pindex->nHeight <= chainActive.Height() - nCheckDepth) {
             break;
         }
 
         if (fPruneMode && !pindex->nStatus.hasData()) {
             // If pruning, only go back as far as we have data.
             LogPrintf("VerifyDB(): block verification stopping at height %d "
                       "(pruning, no data)\n",
                       pindex->nHeight);
             break;
         }
 
         CBlock block;
 
         // check level 0: read from disk
         if (!ReadBlockFromDisk(block, pindex, consensusParams)) {
             return error(
                 "VerifyDB(): *** ReadBlockFromDisk failed at %d, hash=%s",
                 pindex->nHeight, pindex->GetBlockHash().ToString());
         }
 
         // check level 1: verify block validity
         if (nCheckLevel >= 1 && !CheckBlock(block, state, consensusParams,
                                             BlockValidationOptions(config))) {
             return error("%s: *** found bad block at %d, hash=%s (%s)\n",
                          __func__, pindex->nHeight,
                          pindex->GetBlockHash().ToString(),
                          FormatStateMessage(state));
         }
 
         // check level 2: verify undo validity
         if (nCheckLevel >= 2 && pindex) {
             CBlockUndo undo;
             if (!pindex->GetUndoPos().IsNull()) {
                 if (!UndoReadFromDisk(undo, pindex)) {
                     return error(
                         "VerifyDB(): *** found bad undo data at %d, hash=%s\n",
                         pindex->nHeight, pindex->GetBlockHash().ToString());
                 }
             }
         }
 
         // check level 3: check for inconsistencies during memory-only
         // disconnect of tip blocks
         if (nCheckLevel >= 3 &&
             (coins.DynamicMemoryUsage() + pcoinsTip->DynamicMemoryUsage()) <=
                 nCoinCacheUsage) {
             assert(coins.GetBestBlock() == pindex->GetBlockHash());
             DisconnectResult res =
                 g_chainstate.DisconnectBlock(block, pindex, coins);
             if (res == DISCONNECT_FAILED) {
                 return error("VerifyDB(): *** irrecoverable inconsistency in "
                              "block data at %d, hash=%s",
                              pindex->nHeight,
                              pindex->GetBlockHash().ToString());
             }
 
             if (res == DISCONNECT_UNCLEAN) {
                 nGoodTransactions = 0;
                 pindexFailure = pindex;
             } else {
                 nGoodTransactions += block.vtx.size();
             }
         }
 
         if (ShutdownRequested()) {
             return true;
         }
     }
 
     if (pindexFailure) {
         return error("VerifyDB(): *** coin database inconsistencies found "
                      "(last %i blocks, %i good transactions before that)\n",
                      chainActive.Height() - pindexFailure->nHeight + 1,
                      nGoodTransactions);
     }
 
     // store block count as we move pindex at check level >= 4
     int block_count = chainActive.Height() - pindex->nHeight;
 
     // check level 4: try reconnecting blocks
     if (nCheckLevel >= 4) {
         while (pindex != chainActive.Tip()) {
             boost::this_thread::interruption_point();
             uiInterface.ShowProgress(
                 _("Verifying blocks..."),
                 std::max(
                     1, std::min(99, 100 - (int)(((double)(chainActive.Height() -
                                                           pindex->nHeight)) /
                                                 (double)nCheckDepth * 50))),
                 false);
             pindex = chainActive.Next(pindex);
             CBlock block;
             if (!ReadBlockFromDisk(block, pindex, consensusParams)) {
                 return error(
                     "VerifyDB(): *** ReadBlockFromDisk failed at %d, hash=%s",
                     pindex->nHeight, pindex->GetBlockHash().ToString());
             }
             if (!g_chainstate.ConnectBlock(block, state, pindex, coins, params,
                                            BlockValidationOptions(config))) {
                 return error("VerifyDB(): *** found unconnectable block at %d, "
                              "hash=%s (%s)",
                              pindex->nHeight, pindex->GetBlockHash().ToString(),
                              FormatStateMessage(state));
             }
         }
     }
 
     LogPrintf("[DONE].\n");
     LogPrintf("No coin database inconsistencies in last %i blocks (%i "
               "transactions)\n",
               block_count, nGoodTransactions);
 
     return true;
 }
 
 /**
  * Apply the effects of a block on the utxo cache, ignoring that it may already
  * have been applied.
  */
 bool CChainState::RollforwardBlock(const CBlockIndex *pindex,
                                    CCoinsViewCache &view,
                                    const Consensus::Params &params) {
     // TODO: merge with ConnectBlock
     CBlock block;
     if (!ReadBlockFromDisk(block, pindex, params)) {
         return error("ReplayBlock(): ReadBlockFromDisk failed at %d, hash=%s",
                      pindex->nHeight, pindex->GetBlockHash().ToString());
     }
 
     for (const CTransactionRef &tx : block.vtx) {
         // Pass check = true as every addition may be an overwrite.
         AddCoins(view, *tx, pindex->nHeight, true);
     }
 
     for (const CTransactionRef &tx : block.vtx) {
         if (tx->IsCoinBase()) {
             continue;
         }
 
         for (const CTxIn &txin : tx->vin) {
             view.SpendCoin(txin.prevout);
         }
     }
 
     return true;
 }
 
 bool CChainState::ReplayBlocks(const Consensus::Params &params,
                                CCoinsView *view) {
     LOCK(cs_main);
 
     CCoinsViewCache cache(view);
 
     std::vector<BlockHash> hashHeads = view->GetHeadBlocks();
     if (hashHeads.empty()) {
         // We're already in a consistent state.
         return true;
     }
 
     if (hashHeads.size() != 2) {
         return error("ReplayBlocks(): unknown inconsistent state");
     }
 
     uiInterface.ShowProgress(_("Replaying blocks..."), 0, false);
     LogPrintf("Replaying blocks\n");
 
     // Old tip during the interrupted flush.
     const CBlockIndex *pindexOld = nullptr;
     // New tip during the interrupted flush.
     const CBlockIndex *pindexNew;
     // Latest block common to both the old and the new tip.
     const CBlockIndex *pindexFork = nullptr;
 
     if (mapBlockIndex.count(hashHeads[0]) == 0) {
         return error(
             "ReplayBlocks(): reorganization to unknown block requested");
     }
 
     pindexNew = mapBlockIndex[hashHeads[0]];
 
     if (!hashHeads[1].IsNull()) {
         // The old tip is allowed to be 0, indicating it's the first flush.
         if (mapBlockIndex.count(hashHeads[1]) == 0) {
             return error(
                 "ReplayBlocks(): reorganization from unknown block requested");
         }
 
         pindexOld = mapBlockIndex[hashHeads[1]];
         pindexFork = LastCommonAncestor(pindexOld, pindexNew);
         assert(pindexFork != nullptr);
     }
 
     // Rollback along the old branch.
     while (pindexOld != pindexFork) {
         if (pindexOld->nHeight > 0) {
             // Never disconnect the genesis block.
             CBlock block;
             if (!ReadBlockFromDisk(block, pindexOld, params)) {
                 return error("RollbackBlock(): ReadBlockFromDisk() failed at "
                              "%d, hash=%s",
                              pindexOld->nHeight,
                              pindexOld->GetBlockHash().ToString());
             }
 
             LogPrintf("Rolling back %s (%i)\n",
                       pindexOld->GetBlockHash().ToString(), pindexOld->nHeight);
             DisconnectResult res = DisconnectBlock(block, pindexOld, cache);
             if (res == DISCONNECT_FAILED) {
                 return error(
                     "RollbackBlock(): DisconnectBlock failed at %d, hash=%s",
                     pindexOld->nHeight, pindexOld->GetBlockHash().ToString());
             }
 
             // If DISCONNECT_UNCLEAN is returned, it means a non-existing UTXO
             // was deleted, or an existing UTXO was overwritten. It corresponds
             // to cases where the block-to-be-disconnect never had all its
             // operations applied to the UTXO set. However, as both writing a
             // UTXO and deleting a UTXO are idempotent operations, the result is
             // still a version of the UTXO set with the effects of that block
             // undone.
         }
         pindexOld = pindexOld->pprev;
     }
 
     // Roll forward from the forking point to the new tip.
     int nForkHeight = pindexFork ? pindexFork->nHeight : 0;
     for (int nHeight = nForkHeight + 1; nHeight <= pindexNew->nHeight;
          ++nHeight) {
         const CBlockIndex *pindex = pindexNew->GetAncestor(nHeight);
         LogPrintf("Rolling forward %s (%i)\n",
                   pindex->GetBlockHash().ToString(), nHeight);
         if (!RollforwardBlock(pindex, cache, params)) {
             return false;
         }
     }
 
     cache.SetBestBlock(pindexNew->GetBlockHash());
     cache.Flush();
     uiInterface.ShowProgress("", 100, false);
     return true;
 }
 
 bool ReplayBlocks(const Consensus::Params &params, CCoinsView *view) {
     return g_chainstate.ReplayBlocks(params, view);
 }
 
 // May NOT be used after any connections are up as much of the peer-processing
 // logic assumes a consistent block index state
 void CChainState::UnloadBlockIndex() {
     nBlockSequenceId = 1;
     m_failed_blocks.clear();
     setBlockIndexCandidates.clear();
 }
 
 // May NOT be used after any connections are up as much
 // of the peer-processing logic assumes a consistent
 // block index state
 void UnloadBlockIndex() {
     LOCK(cs_main);
     chainActive.SetTip(nullptr);
     pindexFinalized = nullptr;
     pindexBestInvalid = nullptr;
     pindexBestParked = nullptr;
     pindexBestHeader = nullptr;
     pindexBestForkTip = nullptr;
     pindexBestForkBase = nullptr;
     g_mempool.clear();
     mapBlocksUnlinked.clear();
     vinfoBlockFile.clear();
     nLastBlockFile = 0;
     setDirtyBlockIndex.clear();
     setDirtyFileInfo.clear();
 
     for (const BlockMap::value_type &entry : mapBlockIndex) {
         delete entry.second;
     }
 
     mapBlockIndex.clear();
     fHavePruned = false;
 
     g_chainstate.UnloadBlockIndex();
 }
 
 bool LoadBlockIndex(const Config &config) {
     // Load block index from databases
     bool needs_init = fReindex;
     if (!fReindex) {
         bool ret = LoadBlockIndexDB(config);
         if (!ret) {
             return false;
         }
 
         needs_init = mapBlockIndex.empty();
     }
 
     if (needs_init) {
         // Everything here is for *new* reindex/DBs. Thus, though
         // LoadBlockIndexDB may have set fReindex if we shut down
         // mid-reindex previously, we don't check fReindex and
         // instead only check it prior to LoadBlockIndexDB to set
         // needs_init.
 
         LogPrintf("Initializing databases...\n");
     }
     return true;
 }
 
 bool CChainState::LoadGenesisBlock(const CChainParams &chainparams) {
     LOCK(cs_main);
 
     // Check whether we're already initialized by checking for genesis in
     // mapBlockIndex. Note that we can't use chainActive here, since it is
     // set based on the coins db, not the block index db, which is the only
     // thing loaded at this point.
     if (mapBlockIndex.count(chainparams.GenesisBlock().GetHash())) {
         return true;
     }
 
     try {
         const CBlock &block = chainparams.GenesisBlock();
         FlatFilePos blockPos = SaveBlockToDisk(block, 0, chainparams, nullptr);
         if (blockPos.IsNull()) {
             return error("%s: writing genesis block to disk failed", __func__);
         }
         CBlockIndex *pindex = AddToBlockIndex(block);
         ReceivedBlockTransactions(block, pindex, blockPos);
     } catch (const std::runtime_error &e) {
         return error("%s: failed to write genesis block: %s", __func__,
                      e.what());
     }
 
     return true;
 }
 
 bool LoadGenesisBlock(const CChainParams &chainparams) {
     return g_chainstate.LoadGenesisBlock(chainparams);
 }
 
 bool LoadExternalBlockFile(const Config &config, FILE *fileIn,
                            FlatFilePos *dbp) {
     // Map of disk positions for blocks with unknown parent (only used for
     // reindex)
     static std::multimap<uint256, FlatFilePos> mapBlocksUnknownParent;
     int64_t nStart = GetTimeMillis();
 
     const CChainParams &chainparams = config.GetChainParams();
 
     int nLoaded = 0;
     try {
         // This takes over fileIn and calls fclose() on it in the CBufferedFile
         // destructor. Make sure we have at least 2*MAX_TX_SIZE space in there
         // so any transaction can fit in the buffer.
         CBufferedFile blkdat(fileIn, 2 * MAX_TX_SIZE, MAX_TX_SIZE + 8, SER_DISK,
                              CLIENT_VERSION);
         uint64_t nRewind = blkdat.GetPos();
         while (!blkdat.eof()) {
             boost::this_thread::interruption_point();
 
             blkdat.SetPos(nRewind);
             // Start one byte further next time, in case of failure.
             nRewind++;
             // Remove former limit.
             blkdat.SetLimit();
             unsigned int nSize = 0;
             try {
                 // Locate a header.
                 uint8_t buf[CMessageHeader::MESSAGE_START_SIZE];
                 blkdat.FindByte(chainparams.DiskMagic()[0]);
                 nRewind = blkdat.GetPos() + 1;
                 blkdat >> buf;
                 if (memcmp(buf, chainparams.DiskMagic().data(),
                            CMessageHeader::MESSAGE_START_SIZE)) {
                     continue;
                 }
 
                 // Read size.
                 blkdat >> nSize;
                 if (nSize < 80) {
                     continue;
                 }
             } catch (const std::exception &) {
                 // No valid block header found; don't complain.
                 break;
             }
 
             try {
                 // read block
                 uint64_t nBlockPos = blkdat.GetPos();
                 if (dbp) {
                     dbp->nPos = nBlockPos;
                 }
                 blkdat.SetLimit(nBlockPos + nSize);
                 blkdat.SetPos(nBlockPos);
                 std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
                 CBlock &block = *pblock;
                 blkdat >> block;
                 nRewind = blkdat.GetPos();
 
                 const BlockHash hash = block.GetHash();
                 {
                     LOCK(cs_main);
                     // detect out of order blocks, and store them for later
                     if (hash != chainparams.GetConsensus().hashGenesisBlock &&
                         !LookupBlockIndex(block.hashPrevBlock)) {
                         LogPrint(
                             BCLog::REINDEX,
                             "%s: Out of order block %s, parent %s not known\n",
                             __func__, hash.ToString(),
                             block.hashPrevBlock.ToString());
                         if (dbp) {
                             mapBlocksUnknownParent.insert(
                                 std::make_pair(block.hashPrevBlock, *dbp));
                         }
                         continue;
                     }
 
                     // process in case the block isn't known yet
                     CBlockIndex *pindex = LookupBlockIndex(hash);
                     if (!pindex || !pindex->nStatus.hasData()) {
                         CValidationState state;
                         if (g_chainstate.AcceptBlock(config, pblock, state,
                                                      true, dbp, nullptr)) {
                             nLoaded++;
                         }
                         if (state.IsError()) {
                             break;
                         }
                     } else if (hash != chainparams.GetConsensus()
                                            .hashGenesisBlock &&
                                pindex->nHeight % 1000 == 0) {
                         LogPrint(
                             BCLog::REINDEX,
                             "Block Import: already had block %s at height %d\n",
                             hash.ToString(), pindex->nHeight);
                     }
                 }
 
                 // Activate the genesis block so normal node progress can
                 // continue
                 if (hash == chainparams.GetConsensus().hashGenesisBlock) {
                     CValidationState state;
                     if (!ActivateBestChain(config, state)) {
                         break;
                     }
                 }
 
                 NotifyHeaderTip();
 
                 // Recursively process earlier encountered successors of this
                 // block
                 std::deque<uint256> queue;
                 queue.push_back(hash);
                 while (!queue.empty()) {
                     uint256 head = queue.front();
                     queue.pop_front();
                     std::pair<std::multimap<uint256, FlatFilePos>::iterator,
                               std::multimap<uint256, FlatFilePos>::iterator>
                         range = mapBlocksUnknownParent.equal_range(head);
                     while (range.first != range.second) {
                         std::multimap<uint256, FlatFilePos>::iterator it =
                             range.first;
                         std::shared_ptr<CBlock> pblockrecursive =
                             std::make_shared<CBlock>();
                         if (ReadBlockFromDisk(*pblockrecursive, it->second,
                                               chainparams.GetConsensus())) {
                             LogPrint(
                                 BCLog::REINDEX,
                                 "%s: Processing out of order child %s of %s\n",
                                 __func__, pblockrecursive->GetHash().ToString(),
                                 head.ToString());
                             LOCK(cs_main);
                             CValidationState dummy;
                             if (g_chainstate.AcceptBlock(
                                     config, pblockrecursive, dummy, true,
                                     &it->second, nullptr)) {
                                 nLoaded++;
                                 queue.push_back(pblockrecursive->GetHash());
                             }
                         }
                         range.first++;
                         mapBlocksUnknownParent.erase(it);
                         NotifyHeaderTip();
                     }
                 }
             } catch (const std::exception &e) {
                 LogPrintf("%s: Deserialize or I/O error - %s\n", __func__,
                           e.what());
             }
         }
     } catch (const std::runtime_error &e) {
         AbortNode(std::string("System error: ") + e.what());
     }
 
     if (nLoaded > 0) {
         LogPrintf("Loaded %i blocks from external file in %dms\n", nLoaded,
                   GetTimeMillis() - nStart);
     }
 
     return nLoaded > 0;
 }
 
 void CChainState::CheckBlockIndex(const Consensus::Params &consensusParams) {
     if (!fCheckBlockIndex) {
         return;
     }
 
     LOCK(cs_main);
 
     // During a reindex, we read the genesis block and call CheckBlockIndex
     // before ActivateBestChain, so we have the genesis block in mapBlockIndex
     // but no active chain. (A few of the tests when iterating the block tree
     // require that chainActive has been initialized.)
     if (chainActive.Height() < 0) {
         assert(mapBlockIndex.size() <= 1);
         return;
     }
 
     // Build forward-pointing map of the entire block tree.
     std::multimap<CBlockIndex *, CBlockIndex *> forward;
     for (const auto &entry : mapBlockIndex) {
         forward.emplace(entry.second->pprev, entry.second);
     }
 
     assert(forward.size() == mapBlockIndex.size());
 
     std::pair<std::multimap<CBlockIndex *, CBlockIndex *>::iterator,
               std::multimap<CBlockIndex *, CBlockIndex *>::iterator>
         rangeGenesis = forward.equal_range(nullptr);
     CBlockIndex *pindex = rangeGenesis.first->second;
     rangeGenesis.first++;
     // There is only one index entry with parent nullptr.
     assert(rangeGenesis.first == rangeGenesis.second);
 
     // Iterate over the entire block tree, using depth-first search.
     // Along the way, remember whether there are blocks on the path from genesis
     // block being explored which are the first to have certain properties.
     size_t nNodes = 0;
     int nHeight = 0;
     // Oldest ancestor of pindex which is invalid.
     CBlockIndex *pindexFirstInvalid = nullptr;
     // Oldest ancestor of pindex which is parked.
     CBlockIndex *pindexFirstParked = nullptr;
     // Oldest ancestor of pindex which does not have data available.
     CBlockIndex *pindexFirstMissing = nullptr;
     // Oldest ancestor of pindex for which nTx == 0.
     CBlockIndex *pindexFirstNeverProcessed = nullptr;
     // Oldest ancestor of pindex which does not have BLOCK_VALID_TREE
     // (regardless of being valid or not).
     CBlockIndex *pindexFirstNotTreeValid = nullptr;
     // Oldest ancestor of pindex which does not have BLOCK_VALID_TRANSACTIONS
     // (regardless of being valid or not).
     CBlockIndex *pindexFirstNotTransactionsValid = nullptr;
     // Oldest ancestor of pindex which does not have BLOCK_VALID_CHAIN
     // (regardless of being valid or not).
     CBlockIndex *pindexFirstNotChainValid = nullptr;
     // Oldest ancestor of pindex which does not have BLOCK_VALID_SCRIPTS
     // (regardless of being valid or not).
     CBlockIndex *pindexFirstNotScriptsValid = nullptr;
     while (pindex != nullptr) {
         nNodes++;
         if (pindexFirstInvalid == nullptr && pindex->nStatus.hasFailed()) {
             pindexFirstInvalid = pindex;
         }
         if (pindexFirstParked == nullptr && pindex->nStatus.isParked()) {
             pindexFirstParked = pindex;
         }
         if (pindexFirstMissing == nullptr && !pindex->nStatus.hasData()) {
             pindexFirstMissing = pindex;
         }
         if (pindexFirstNeverProcessed == nullptr && pindex->nTx == 0) {
             pindexFirstNeverProcessed = pindex;
         }
         if (pindex->pprev != nullptr && pindexFirstNotTreeValid == nullptr &&
             pindex->nStatus.getValidity() < BlockValidity::TREE) {
             pindexFirstNotTreeValid = pindex;
         }
         if (pindex->pprev != nullptr &&
             pindexFirstNotTransactionsValid == nullptr &&
             pindex->nStatus.getValidity() < BlockValidity::TRANSACTIONS) {
             pindexFirstNotTransactionsValid = pindex;
         }
         if (pindex->pprev != nullptr && pindexFirstNotChainValid == nullptr &&
             pindex->nStatus.getValidity() < BlockValidity::CHAIN) {
             pindexFirstNotChainValid = pindex;
         }
         if (pindex->pprev != nullptr && pindexFirstNotScriptsValid == nullptr &&
             pindex->nStatus.getValidity() < BlockValidity::SCRIPTS) {
             pindexFirstNotScriptsValid = pindex;
         }
 
         // Begin: actual consistency checks.
         if (pindex->pprev == nullptr) {
             // Genesis block checks.
             // Genesis block's hash must match.
             assert(pindex->GetBlockHash() == consensusParams.hashGenesisBlock);
             // The current active chain's genesis block must be this block.
             assert(pindex == chainActive.Genesis());
         }
         if (!pindex->HaveTxsDownloaded()) {
             // nSequenceId can't be set positive for blocks that aren't linked
             // (negative is used for preciousblock)
             assert(pindex->nSequenceId <= 0);
         }
         // VALID_TRANSACTIONS is equivalent to nTx > 0 for all nodes (whether or
         // not pruning has occurred). HAVE_DATA is only equivalent to nTx > 0
         // (or VALID_TRANSACTIONS) if no pruning has occurred.
         if (!fHavePruned) {
             // If we've never pruned, then HAVE_DATA should be equivalent to nTx
             // > 0
             assert(pindex->nStatus.hasData() == (pindex->nTx > 0));
             assert(pindexFirstMissing == pindexFirstNeverProcessed);
         } else if (pindex->nStatus.hasData()) {
             // If we have pruned, then we can only say that HAVE_DATA implies
             // nTx > 0
             assert(pindex->nTx > 0);
         }
         if (pindex->nStatus.hasUndo()) {
             assert(pindex->nStatus.hasData());
         }
         // This is pruning-independent.
         assert((pindex->nStatus.getValidity() >= BlockValidity::TRANSACTIONS) ==
                (pindex->nTx > 0));
         // All parents having had data (at some point) is equivalent to all
         // parents being VALID_TRANSACTIONS, which is equivalent to
         // HaveTxsDownloaded(). All parents having had data (at some point) is
         // equivalent to all parents being VALID_TRANSACTIONS, which is
         // equivalent to HaveTxsDownloaded().
         assert((pindexFirstNeverProcessed == nullptr) ==
                (pindex->HaveTxsDownloaded()));
         assert((pindexFirstNotTransactionsValid == nullptr) ==
                (pindex->HaveTxsDownloaded()));
         // nHeight must be consistent.
         assert(pindex->nHeight == nHeight);
         // For every block except the genesis block, the chainwork must be
         // larger than the parent's.
         assert(pindex->pprev == nullptr ||
                pindex->nChainWork >= pindex->pprev->nChainWork);
         // The pskip pointer must point back for all but the first 2 blocks.
         assert(nHeight < 2 ||
                (pindex->pskip && (pindex->pskip->nHeight < nHeight)));
         // All mapBlockIndex entries must at least be TREE valid
         assert(pindexFirstNotTreeValid == nullptr);
         if (pindex->nStatus.getValidity() >= BlockValidity::TREE) {
             // TREE valid implies all parents are TREE valid
             assert(pindexFirstNotTreeValid == nullptr);
         }
         if (pindex->nStatus.getValidity() >= BlockValidity::CHAIN) {
             // CHAIN valid implies all parents are CHAIN valid
             assert(pindexFirstNotChainValid == nullptr);
         }
         if (pindex->nStatus.getValidity() >= BlockValidity::SCRIPTS) {
             // SCRIPTS valid implies all parents are SCRIPTS valid
             assert(pindexFirstNotScriptsValid == nullptr);
         }
         if (pindexFirstInvalid == nullptr) {
             // Checks for not-invalid blocks.
             // The failed mask cannot be set for blocks without invalid parents.
             assert(!pindex->nStatus.isInvalid());
         }
         if (pindexFirstParked == nullptr) {
             // Checks for not-parked blocks.
             // The parked mask cannot be set for blocks without parked parents.
             // (i.e., hasParkedParent only if an ancestor is properly parked).
             assert(!pindex->nStatus.isOnParkedChain());
         }
         if (!CBlockIndexWorkComparator()(pindex, chainActive.Tip()) &&
             pindexFirstNeverProcessed == nullptr) {
             if (pindexFirstInvalid == nullptr) {
                 // If this block sorts at least as good as the current tip and
                 // is valid and we have all data for its parents, it must be in
                 // setBlockIndexCandidates or be parked.
                 if (pindexFirstMissing == nullptr) {
                     assert(pindex->nStatus.isOnParkedChain() ||
                            setBlockIndexCandidates.count(pindex));
                 }
                 // chainActive.Tip() must also be there even if some data has
                 // been pruned.
                 if (pindex == chainActive.Tip()) {
                     assert(setBlockIndexCandidates.count(pindex));
                 }
                 // If some parent is missing, then it could be that this block
                 // was in setBlockIndexCandidates but had to be removed because
                 // of the missing data. In this case it must be in
                 // mapBlocksUnlinked -- see test below.
             }
         } else {
             // If this block sorts worse than the current tip or some ancestor's
             // block has never been seen, it cannot be in
             // setBlockIndexCandidates.
             assert(setBlockIndexCandidates.count(pindex) == 0);
         }
         // Check whether this block is in mapBlocksUnlinked.
         std::pair<std::multimap<CBlockIndex *, CBlockIndex *>::iterator,
                   std::multimap<CBlockIndex *, CBlockIndex *>::iterator>
             rangeUnlinked = mapBlocksUnlinked.equal_range(pindex->pprev);
         bool foundInUnlinked = false;
         while (rangeUnlinked.first != rangeUnlinked.second) {
             assert(rangeUnlinked.first->first == pindex->pprev);
             if (rangeUnlinked.first->second == pindex) {
                 foundInUnlinked = true;
                 break;
             }
             rangeUnlinked.first++;
         }
         if (pindex->pprev && pindex->nStatus.hasData() &&
             pindexFirstNeverProcessed != nullptr &&
             pindexFirstInvalid == nullptr) {
             // If this block has block data available, some parent was never
             // received, and has no invalid parents, it must be in
             // mapBlocksUnlinked.
             assert(foundInUnlinked);
         }
         if (!pindex->nStatus.hasData()) {
             // Can't be in mapBlocksUnlinked if we don't HAVE_DATA
             assert(!foundInUnlinked);
         }
         if (pindexFirstMissing == nullptr) {
             // We aren't missing data for any parent -- cannot be in
             // mapBlocksUnlinked.
             assert(!foundInUnlinked);
         }
         if (pindex->pprev && pindex->nStatus.hasData() &&
             pindexFirstNeverProcessed == nullptr &&
             pindexFirstMissing != nullptr) {
             // We HAVE_DATA for this block, have received data for all parents
             // at some point, but we're currently missing data for some parent.
             // We must have pruned.
             assert(fHavePruned);
             // This block may have entered mapBlocksUnlinked if:
             //  - it has a descendant that at some point had more work than the
             //    tip, and
             //  - we tried switching to that descendant but were missing
             //    data for some intermediate block between chainActive and the
             //    tip.
             // So if this block is itself better than chainActive.Tip() and it
             // wasn't in
             // setBlockIndexCandidates, then it must be in mapBlocksUnlinked.
             if (!CBlockIndexWorkComparator()(pindex, chainActive.Tip()) &&
                 setBlockIndexCandidates.count(pindex) == 0) {
                 if (pindexFirstInvalid == nullptr) {
                     assert(foundInUnlinked);
                 }
             }
         }
         // Perhaps too slow
         // assert(pindex->GetBlockHash() == pindex->GetBlockHeader().GetHash());
         // End: actual consistency checks.
 
         // Try descending into the first subnode.
         std::pair<std::multimap<CBlockIndex *, CBlockIndex *>::iterator,
                   std::multimap<CBlockIndex *, CBlockIndex *>::iterator>
             range = forward.equal_range(pindex);
         if (range.first != range.second) {
             // A subnode was found.
             pindex = range.first->second;
             nHeight++;
             continue;
         }
         // This is a leaf node. Move upwards until we reach a node of which we
         // have not yet visited the last child.
         while (pindex) {
             // We are going to either move to a parent or a sibling of pindex.
             // If pindex was the first with a certain property, unset the
             // corresponding variable.
             if (pindex == pindexFirstInvalid) {
                 pindexFirstInvalid = nullptr;
             }
             if (pindex == pindexFirstParked) {
                 pindexFirstParked = nullptr;
             }
             if (pindex == pindexFirstMissing) {
                 pindexFirstMissing = nullptr;
             }
             if (pindex == pindexFirstNeverProcessed) {
                 pindexFirstNeverProcessed = nullptr;
             }
             if (pindex == pindexFirstNotTreeValid) {
                 pindexFirstNotTreeValid = nullptr;
             }
             if (pindex == pindexFirstNotTransactionsValid) {
                 pindexFirstNotTransactionsValid = nullptr;
             }
             if (pindex == pindexFirstNotChainValid) {
                 pindexFirstNotChainValid = nullptr;
             }
             if (pindex == pindexFirstNotScriptsValid) {
                 pindexFirstNotScriptsValid = nullptr;
             }
             // Find our parent.
             CBlockIndex *pindexPar = pindex->pprev;
             // Find which child we just visited.
             std::pair<std::multimap<CBlockIndex *, CBlockIndex *>::iterator,
                       std::multimap<CBlockIndex *, CBlockIndex *>::iterator>
                 rangePar = forward.equal_range(pindexPar);
             while (rangePar.first->second != pindex) {
                 // Our parent must have at least the node we're coming from as
                 // child.
                 assert(rangePar.first != rangePar.second);
                 rangePar.first++;
             }
             // Proceed to the next one.
             rangePar.first++;
             if (rangePar.first != rangePar.second) {
                 // Move to the sibling.
                 pindex = rangePar.first->second;
                 break;
             } else {
                 // Move up further.
                 pindex = pindexPar;
                 nHeight--;
                 continue;
             }
         }
     }
 
     // Check that we actually traversed the entire map.
     assert(nNodes == forward.size());
 }
 
 std::string CBlockFileInfo::ToString() const {
     return strprintf(
         "CBlockFileInfo(blocks=%u, size=%u, heights=%u...%u, time=%s...%s)",
         nBlocks, nSize, nHeightFirst, nHeightLast,
         FormatISO8601DateTime(nTimeFirst), FormatISO8601DateTime(nTimeLast));
 }
 
 CBlockFileInfo *GetBlockFileInfo(size_t n) {
     LOCK(cs_LastBlockFile);
 
     return &vinfoBlockFile.at(n);
 }
 
 ThresholdState VersionBitsTipState(const Consensus::Params &params,
                                    Consensus::DeploymentPos pos) {
     LOCK(cs_main);
     return VersionBitsState(chainActive.Tip(), params, pos, versionbitscache);
 }
 
 BIP9Stats VersionBitsTipStatistics(const Consensus::Params &params,
                                    Consensus::DeploymentPos pos) {
     LOCK(cs_main);
     return VersionBitsStatistics(chainActive.Tip(), params, pos);
 }
 
 int VersionBitsTipStateSinceHeight(const Consensus::Params &params,
                                    Consensus::DeploymentPos pos) {
     LOCK(cs_main);
     return VersionBitsStateSinceHeight(chainActive.Tip(), params, pos,
                                        versionbitscache);
 }
 
 static const uint64_t MEMPOOL_DUMP_VERSION = 1;
 
 bool LoadMempool(const Config &config, CTxMemPool &pool) {
     int64_t nExpiryTimeout =
         gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60;
     FILE *filestr = fsbridge::fopen(GetDataDir() / "mempool.dat", "rb");
     CAutoFile file(filestr, SER_DISK, CLIENT_VERSION);
     if (file.IsNull()) {
         LogPrintf(
             "Failed to open mempool file from disk. Continuing anyway.\n");
         return false;
     }
 
     int64_t count = 0;
     int64_t expired = 0;
     int64_t failed = 0;
     int64_t already_there = 0;
     int64_t nNow = GetTime();
 
     try {
         uint64_t version;
         file >> version;
         if (version != MEMPOOL_DUMP_VERSION) {
             return false;
         }
 
         uint64_t num;
         file >> num;
         while (num--) {
             CTransactionRef tx;
             int64_t nTime;
             int64_t nFeeDelta;
             file >> tx;
             file >> nTime;
             file >> nFeeDelta;
 
             Amount amountdelta = nFeeDelta * SATOSHI;
             if (amountdelta != Amount::zero()) {
                 pool.PrioritiseTransaction(tx->GetId(), amountdelta);
             }
             CValidationState state;
             if (nTime + nExpiryTimeout > nNow) {
                 LOCK(cs_main);
                 AcceptToMemoryPoolWithTime(
                     config, pool, state, tx, nullptr /* pfMissingInputs */,
                     nTime, false /* bypass_limits */,
                     Amount::zero() /* nAbsurdFee */, false /* test_accept */);
                 if (state.IsValid()) {
                     ++count;
                 } else {
                     // mempool may contain the transaction already, e.g. from
                     // wallet(s) having loaded it while we were processing
                     // mempool transactions; consider these as valid, instead of
                     // failed, but mark them as 'already there'
                     if (pool.exists(tx->GetId())) {
                         ++already_there;
                     } else {
                         ++failed;
                     }
                 }
             } else {
                 ++expired;
             }
 
             if (ShutdownRequested()) {
                 return false;
             }
         }
         std::map<TxId, Amount> mapDeltas;
         file >> mapDeltas;
 
         for (const auto &i : mapDeltas) {
             pool.PrioritiseTransaction(i.first, i.second);
         }
     } catch (const std::exception &e) {
         LogPrintf("Failed to deserialize mempool data on disk: %s. Continuing "
                   "anyway.\n",
                   e.what());
         return false;
     }
 
     LogPrintf("Imported mempool transactions from disk: %i succeeded, %i "
               "failed, %i expired, %i already there\n",
               count, failed, expired, already_there);
     return true;
 }
 
 bool DumpMempool(const CTxMemPool &pool) {
     int64_t start = GetTimeMicros();
 
     std::map<uint256, Amount> mapDeltas;
     std::vector<TxMempoolInfo> vinfo;
 
     static Mutex dump_mutex;
     LOCK(dump_mutex);
 
     {
         LOCK(pool.cs);
         for (const auto &i : pool.mapDeltas) {
             mapDeltas[i.first] = i.second;
         }
 
         vinfo = pool.infoAll();
     }
 
     int64_t mid = GetTimeMicros();
 
     try {
         FILE *filestr = fsbridge::fopen(GetDataDir() / "mempool.dat.new", "wb");
         if (!filestr) {
             return false;
         }
 
         CAutoFile file(filestr, SER_DISK, CLIENT_VERSION);
 
         uint64_t version = MEMPOOL_DUMP_VERSION;
         file << version;
 
         file << uint64_t(vinfo.size());
         for (const auto &i : vinfo) {
             file << *(i.tx);
             file << int64_t(i.nTime);
             file << i.nFeeDelta;
             mapDeltas.erase(i.tx->GetId());
         }
 
         file << mapDeltas;
         if (!FileCommit(file.Get())) {
             throw std::runtime_error("FileCommit failed");
         }
         file.fclose();
         RenameOver(GetDataDir() / "mempool.dat.new",
                    GetDataDir() / "mempool.dat");
         int64_t last = GetTimeMicros();
         LogPrintf("Dumped mempool: %gs to copy, %gs to dump\n",
                   (mid - start) * MICRO, (last - mid) * MICRO);
     } catch (const std::exception &e) {
         LogPrintf("Failed to dump mempool: %s. Continuing anyway.\n", e.what());
         return false;
     }
     return true;
 }
 
 bool IsBlockPruned(const CBlockIndex *pblockindex) {
     return (fHavePruned && !pblockindex->nStatus.hasData() &&
             pblockindex->nTx > 0);
 }
 
 //! Guess how far we are in the verification process at the given block index
 //! require cs_main if pindex has not been validated yet (because nChainTx might
 //! be unset)
 //! This conditional lock requirement might be confusing, see:
 //! https://github.com/bitcoin/bitcoin/issues/15994
 double GuessVerificationProgress(const ChainTxData &data,
                                  const CBlockIndex *pindex) {
     if (pindex == nullptr) {
         return 0.0;
     }
 
     int64_t nNow = time(nullptr);
 
     double fTxTotal;
     if (pindex->nChainTx <= data.nTxCount) {
         fTxTotal = data.nTxCount + (nNow - data.nTime) * data.dTxRate;
     } else {
         fTxTotal =
             pindex->nChainTx + (nNow - pindex->GetBlockTime()) * data.dTxRate;
     }
 
     return pindex->nChainTx / fTxTotal;
 }
 
 class CMainCleanup {
 public:
     CMainCleanup() {}
     ~CMainCleanup() {
         // block headers
         for (const std::pair<const BlockHash, CBlockIndex *> &it :
              mapBlockIndex) {
             delete it.second;
         }
         mapBlockIndex.clear();
     }
 } instance_of_cmaincleanup;
diff --git a/test/functional/abc-block-sigchecks-activation.py b/test/functional/abc-block-sigchecks-activation.py
new file mode 100755
index 0000000000..b04a7754ce
--- /dev/null
+++ b/test/functional/abc-block-sigchecks-activation.py
@@ -0,0 +1,355 @@
+#!/usr/bin/env python3
+# Copyright (c) 2020 The Bitcoin Developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""
+Test activation of block sigchecks limits
+"""
+
+from test_framework.blocktools import (
+    create_block,
+    create_coinbase,
+    make_conform_to_ctor,
+)
+from test_framework.cdefs import (
+    BLOCK_MAXBYTES_MAXSIGCHECKS_RATIO
+)
+from test_framework.messages import (
+    CBlock,
+    COutPoint,
+    CTransaction,
+    CTxIn,
+    CTxOut,
+    FromHex,
+)
+from test_framework.mininode import P2PDataStore
+from test_framework.script import (
+    CScript,
+    OP_CHECKDATASIGVERIFY,
+    OP_3DUP,
+    OP_RETURN,
+    OP_TRUE,
+)
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.txtools import pad_tx
+from test_framework.util import assert_equal
+from collections import deque
+
+# Set test to run with sigops deactivation far in the future.
+SIGCHECKS_ACTIVATION_TIME = 2000000000
+
+# If we don't do this, autoreplay protection will activate before graviton and
+# all our sigs will mysteriously fail.
+REPLAY_PROTECTION_START_TIME = SIGCHECKS_ACTIVATION_TIME * 2
+
+# We are going to use a tiny block size so we don't need to waste too much
+# time with making transactions. (note -- minimum block size is 1000000)
+# (just below a multiple, to test edge case)
+MAXBLOCKSIZE = 8000 * BLOCK_MAXBYTES_MAXSIGCHECKS_RATIO - 1
+assert MAXBLOCKSIZE == 1127999
+
+# Blocks with too many sigchecks from cache give this error in log file:
+BLOCK_SIGCHECKS_CACHED_ERROR = "blk-bad-inputs, CheckInputs exceeded SigChecks limit"
+# Blocks with too many sigchecks discovered during parallel checks give
+# this error in log file:
+BLOCK_SIGCHECKS_PARALLEL_ERROR = "blk-bad-inputs, parallel script check failed"
+
+
+def create_transaction(spendfrom, custom_script, amount=None):
+    # Fund and sign a transaction to a given output.
+    # spendfrom should be a CTransaction with first output to OP_TRUE.
+
+    # custom output will go on position 1, after position 0 which will be
+    # OP_TRUE (so it can be reused).
+    customout = CTxOut(0, bytes(custom_script))
+    # set output amount to required dust if not given
+    customout.nValue = amount or (len(customout.serialize()) + 148) * 3
+
+    ctx = CTransaction()
+    ctx.vin.append(CTxIn(COutPoint(spendfrom.sha256, 0), b''))
+    ctx.vout.append(
+        CTxOut(0, bytes([OP_TRUE])))
+    ctx.vout.append(customout)
+    pad_tx(ctx)
+
+    fee = len(ctx.serialize())
+    ctx.vout[0].nValue = spendfrom.vout[0].nValue - customout.nValue - fee
+    ctx.rehash()
+
+    return ctx
+
+
+def check_for_ban_on_rejected_tx(node, tx, reject_reason=None):
+    """Check we are disconnected when sending a txn that the node rejects,
+    then reconnect after.
+
+    (Can't actually get banned, since bitcoind won't ban local peers.)"""
+    node.p2p.send_txs_and_test(
+        [tx], node, success=False, expect_disconnect=True, reject_reason=reject_reason)
+    node.disconnect_p2ps()
+    node.add_p2p_connection(P2PDataStore())
+
+
+def check_for_ban_on_rejected_block(node, block, reject_reason=None):
+    """Check we are disconnected when sending a block that the node rejects,
+    then reconnect after.
+
+    (Can't actually get banned, since bitcoind won't ban local peers.)"""
+    node.p2p.send_blocks_and_test(
+        [block], node, success=False, reject_reason=reject_reason, expect_disconnect=True)
+    node.disconnect_p2ps()
+    node.add_p2p_connection(P2PDataStore())
+
+
+def check_for_no_ban_on_rejected_tx(node, tx, reject_reason=None):
+    """Check we are not disconnected when sending a txn that the node rejects."""
+    node.p2p.send_txs_and_test(
+        [tx], node, success=False, reject_reason=reject_reason)
+
+
+class BlockSigChecksActivationTest(BitcoinTestFramework):
+
+    def set_test_params(self):
+        self.setup_clean_chain = True
+        self.num_nodes = 1
+        self.block_heights = {}
+        self.extra_args = [["-phononactivationtime={}".format(
+            SIGCHECKS_ACTIVATION_TIME),
+            "-replayprotectionactivationtime={}".format(
+            REPLAY_PROTECTION_START_TIME),
+            "-excessiveblocksize={}".format(MAXBLOCKSIZE),
+            "-blockmaxsize={}".format(MAXBLOCKSIZE)]]
+
+    def getbestblock(self, node):
+        """Get the best block. Register its height so we can use build_block."""
+        block_height = node.getblockcount()
+        blockhash = node.getblockhash(block_height)
+        block = FromHex(CBlock(), node.getblock(blockhash, 0))
+        block.calc_sha256()
+        self.block_heights[block.sha256] = block_height
+        return block
+
+    def build_block(self, parent, transactions=(),
+                    nTime=None, cbextrascript=None):
+        """Make a new block with an OP_1 coinbase output.
+
+        Requires parent to have its height registered."""
+        parent.calc_sha256()
+        block_height = self.block_heights[parent.sha256] + 1
+        block_time = (parent.nTime + 1) if nTime is None else nTime
+
+        block = create_block(
+            parent.sha256, create_coinbase(block_height), block_time)
+        if cbextrascript is not None:
+            block.vtx[0].vout.append(CTxOut(0, cbextrascript))
+            block.vtx[0].rehash()
+        block.vtx.extend(transactions)
+        make_conform_to_ctor(block)
+        block.hashMerkleRoot = block.calc_merkle_root()
+        block.solve()
+        self.block_heights[block.sha256] = block_height
+        return block
+
+    def run_test(self):
+        [node] = self.nodes
+        node.add_p2p_connection(P2PDataStore())
+        # Get out of IBD
+        node.generatetoaddress(1, node.get_deterministic_priv_key().address)
+
+        tip = self.getbestblock(node)
+
+        self.log.info("Create some blocks with OP_1 coinbase for spending.")
+        blocks = []
+        for _ in range(20):
+            tip = self.build_block(tip)
+            blocks.append(tip)
+        node.p2p.send_blocks_and_test(blocks, node, success=True)
+        self.spendable_outputs = deque(block.vtx[0] for block in blocks)
+
+        self.log.info("Mature the blocks.")
+        node.generatetoaddress(100, node.get_deterministic_priv_key().address)
+
+        tip = self.getbestblock(node)
+
+        # To make compact and fast-to-verify transactions, we'll use
+        # CHECKDATASIG over and over with the same data.
+        # (Using the same stuff over and over again means we get to hit the
+        # node's signature cache and don't need to make new signatures every
+        # time.)
+        cds_message = b''
+        # r=1 and s=1 ecdsa, the minimum values.
+        cds_signature = bytes.fromhex('3006020101020101')
+        # Recovered pubkey
+        cds_pubkey = bytes.fromhex(
+            '03089b476b570d66fad5a20ae6188ebbaf793a4c2a228c65f3d79ee8111d56c932')
+
+        def minefunding2(n):
+            """ Mine a block with a bunch of outputs that are very dense
+            sigchecks when spent (2 sigchecks each); return the inputs that can
+            be used to spend. """
+            cds_scriptpubkey = CScript(
+                [cds_message, cds_pubkey, OP_3DUP, OP_CHECKDATASIGVERIFY, OP_CHECKDATASIGVERIFY])
+            # The scriptsig is carefully padded to have size 26, which is the
+            # shortest allowed for 2 sigchecks for mempool admission.
+            # The resulting inputs have size 67 bytes, 33.5 bytes/sigcheck.
+            cds_scriptsig = CScript([b'x' * 16, cds_signature])
+            assert_equal(len(cds_scriptsig), 26)
+
+            self.log.debug("Gen {} with locking script {} unlocking script {} .".format(
+                n, cds_scriptpubkey.hex(), cds_scriptsig.hex()))
+
+            tx = self.spendable_outputs.popleft()
+            usable_inputs = []
+            txes = []
+            for _ in range(n):
+                tx = create_transaction(tx, cds_scriptpubkey)
+                txes.append(tx)
+                usable_inputs.append(
+                    CTxIn(COutPoint(tx.sha256, 1), cds_scriptsig))
+            newtip = self.build_block(tip, txes)
+            node.p2p.send_blocks_and_test([newtip], node)
+            return usable_inputs, newtip
+
+        self.log.info("Funding special coins that have high sigchecks")
+
+        # mine 5000 funded outputs (10000 sigchecks)
+        # will be used pre-activation and post-activation
+        usable_inputs, tip = minefunding2(5000)
+        # assemble them into 50 txes with 100 inputs each (200 sigchecks)
+        submittxes_1 = []
+        while len(usable_inputs) >= 100:
+            tx = CTransaction()
+            tx.vin = [usable_inputs.pop() for _ in range(100)]
+            tx.vout = [CTxOut(0, CScript([OP_RETURN]))]
+            tx.rehash()
+            submittxes_1.append(tx)
+
+        # mine 5000 funded outputs (10000 sigchecks)
+        # will be used post-activation
+        usable_inputs, tip = minefunding2(5000)
+        # assemble them into 50 txes with 100 inputs each (200 sigchecks)
+        submittxes_2 = []
+        while len(usable_inputs) >= 100:
+            tx = CTransaction()
+            tx.vin = [usable_inputs.pop() for _ in range(100)]
+            tx.vout = [CTxOut(0, CScript([OP_RETURN]))]
+            tx.rehash()
+            submittxes_2.append(tx)
+
+        # Activation tests
+
+        self.log.info("Approach to just before upgrade activation")
+        # Move our clock to the uprade time so we will accept such
+        # future-timestamped blocks.
+        node.setmocktime(SIGCHECKS_ACTIVATION_TIME + 10)
+        # Mine six blocks with timestamp starting at
+        # SIGCHECKS_ACTIVATION_TIME-1
+        blocks = []
+        for i in range(-1, 5):
+            tip = self.build_block(tip, nTime=SIGCHECKS_ACTIVATION_TIME + i)
+            blocks.append(tip)
+        node.p2p.send_blocks_and_test(blocks, node)
+        assert_equal(node.getblockchaininfo()[
+                     'mediantime'], SIGCHECKS_ACTIVATION_TIME - 1)
+
+        self.log.info(
+            "The next block will activate, but the activation block itself must follow old rules")
+
+        # Send the 50 txes and get the node to mine as many as possible (it should do all)
+        # The node is happy mining and validating a 10000 sigcheck block before
+        # activation.
+        node.p2p.send_txs_and_test(submittxes_1, node)
+        [blockhash] = node.generatetoaddress(
+            1, node.get_deterministic_priv_key().address)
+        assert_equal(set(node.getblock(blockhash, 1)["tx"][1:]), {
+                     t.hash for t in submittxes_1})
+
+        # We have activated, but let's invalidate that.
+        assert_equal(node.getblockchaininfo()[
+            'mediantime'], SIGCHECKS_ACTIVATION_TIME)
+        node.invalidateblock(blockhash)
+
+        # Try again manually and invalidate that too
+        goodblock = self.build_block(tip, submittxes_1)
+        node.p2p.send_blocks_and_test([goodblock], node)
+        node.invalidateblock(goodblock.hash)
+
+        # All transactions should be back in mempool.
+        assert_equal(set(node.getrawmempool()), {t.hash for t in submittxes_1})
+
+        self.log.info("Mine the activation block itself")
+        tip = self.build_block(tip)
+        node.p2p.send_blocks_and_test([tip], node)
+
+        self.log.info("We have activated!")
+        assert_equal(node.getblockchaininfo()[
+                     'mediantime'], SIGCHECKS_ACTIVATION_TIME)
+
+        # save this tip for later
+        # ~ upgrade_block = tip
+
+        # Transactions still in pool:
+        assert_equal(set(node.getrawmempool()), {t.hash for t in submittxes_1})
+
+        self.log.info("Try sending 10000-sigcheck blocks after activation (limit: {})".format(
+            MAXBLOCKSIZE // BLOCK_MAXBYTES_MAXSIGCHECKS_RATIO))
+        # Send block with same txes we just tried before activation
+        badblock = self.build_block(tip, submittxes_1)
+        check_for_ban_on_rejected_block(
+            node, badblock, reject_reason=BLOCK_SIGCHECKS_CACHED_ERROR)
+
+        self.log.info(
+            "There are too many sigchecks in mempool to mine in a single block. Make sure the node won't mine invalid blocks.")
+        node.generatetoaddress(1, node.get_deterministic_priv_key().address)
+        tip = self.getbestblock(node)
+        # only 39 txes got mined.
+        assert_equal(len(node.getrawmempool()), 11)
+
+        self.log.info("Try sending 10000-sigcheck block with fresh transactions after activation (limit: {})".format(
+            MAXBLOCKSIZE // BLOCK_MAXBYTES_MAXSIGCHECKS_RATIO))
+        # Note: in the following tests we'll be bumping timestamp in order
+        # to bypass any kind of 'bad block' cache on the node, and get a
+        # fresh evaluation each time.
+
+        # Try another block with 10000 sigchecks but all fresh transactions
+        badblock = self.build_block(
+            tip, submittxes_2, nTime=SIGCHECKS_ACTIVATION_TIME + 5)
+        check_for_ban_on_rejected_block(
+            node, badblock, reject_reason=BLOCK_SIGCHECKS_PARALLEL_ERROR)
+
+        # Send the same txes again with different block hash. Currently we don't
+        # cache valid transactions in invalid blocks so nothing changes.
+        badblock = self.build_block(
+            tip, submittxes_2, nTime=SIGCHECKS_ACTIVATION_TIME + 6)
+        check_for_ban_on_rejected_block(
+            node, badblock, reject_reason=BLOCK_SIGCHECKS_PARALLEL_ERROR)
+
+        # Put all the txes in mempool, in order to get them cached:
+        node.p2p.send_txs_and_test(submittxes_2, node)
+        # Send them again, the node still doesn't like it. But the log
+        # error message has now changed because the txes failed from cache.
+        badblock = self.build_block(
+            tip, submittxes_2, nTime=SIGCHECKS_ACTIVATION_TIME + 7)
+        check_for_ban_on_rejected_block(
+            node, badblock, reject_reason=BLOCK_SIGCHECKS_CACHED_ERROR)
+
+        self.log.info("Try sending 8000-sigcheck block after activation (limit: {})".format(
+            MAXBLOCKSIZE // BLOCK_MAXBYTES_MAXSIGCHECKS_RATIO))
+        # redundant, but just to mirror the following test...
+        node.setexcessiveblock(MAXBLOCKSIZE)
+        badblock = self.build_block(
+            tip, submittxes_2[:40], nTime=SIGCHECKS_ACTIVATION_TIME + 5)
+        check_for_ban_on_rejected_block(
+            node, badblock, reject_reason=BLOCK_SIGCHECKS_CACHED_ERROR)
+
+        self.log.info("Bump the excessiveblocksize limit by 1 byte, and send another block with same txes (new sigchecks limit: {})".format(
+            (MAXBLOCKSIZE + 1) // BLOCK_MAXBYTES_MAXSIGCHECKS_RATIO))
+        node.setexcessiveblock(MAXBLOCKSIZE + 1)
+        tip = self.build_block(
+            tip, submittxes_2[:40], nTime=SIGCHECKS_ACTIVATION_TIME + 6)
+        # It should succeed now since limit should be 8000.
+        node.p2p.send_blocks_and_test([tip], node)
+
+
+if __name__ == '__main__':
+    BlockSigChecksActivationTest().main()
diff --git a/test/functional/abc-magnetic-anomaly-mining.py b/test/functional/abc-magnetic-anomaly-mining.py
index c49fd9d817..5f29099dd4 100755
--- a/test/functional/abc-magnetic-anomaly-mining.py
+++ b/test/functional/abc-magnetic-anomaly-mining.py
@@ -1,125 +1,122 @@
 #!/usr/bin/env python3
 # Copyright (c) 2014-2016 The Bitcoin Core developers
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """
 Test that mining RPC continues to supply correct transaction metadata after
 the Nov 2018 protocol upgrade which engages canonical transaction ordering
 """
 
 import decimal
 import random
 import time
 
 from test_framework.test_framework import BitcoinTestFramework
 
-# Set test to run with sigops deactivation far in the future.
-SIGOPS_DEACTIVATION_TIME = 2000000000
-
 
 class CTORMiningTest(BitcoinTestFramework):
     def set_test_params(self):
         # Setup two nodes so we can getblocktemplate
         # it errors out if it is not connected to other nodes
         self.num_nodes = 2
         self.setup_clean_chain = True
         self.block_heights = {}
         self.tip = None
         self.blocks = {}
         self.mocktime = int(time.time()) - 600 * 100
 
-        extra_arg = ['-spendzeroconfchange=0', '-whitelist=127.0.0.1',
-                     '-phononactivationtime={}'.format(SIGOPS_DEACTIVATION_TIME)]
+        extra_arg = ['-spendzeroconfchange=0', '-whitelist=127.0.0.1']
         self.extra_args = [extra_arg, extra_arg]
 
     def skip_test_if_missing_module(self):
         self.skip_if_no_wallet()
 
     def run_test(self):
         mining_node = self.nodes[0]
 
         # Helper for updating the times
         def update_time():
             mining_node.setmocktime(self.mocktime)
             self.mocktime = self.mocktime + 600
 
         mining_node.getnewaddress()
 
         # Generate some unspent utxos and also
         # activate magnetic anomaly
         for x in range(150):
             update_time()
             mining_node.generate(1)
 
         update_time()
         unspent = mining_node.listunspent()
 
         transactions = {}
         # Spend all our coinbases
         while len(unspent):
             inputs = []
             # Grab a random number of inputs
             for _ in range(random.randrange(1, 5)):
                 txin = unspent.pop()
                 inputs.append({
                     'txid': txin['txid'],
                     'vout': 0  # This is a coinbase
                 })
                 if len(unspent) == 0:
                     break
 
             outputs = {}
             # Calculate a unique fee for this transaction
             fee = decimal.Decimal(random.randint(
                 1000, 2000)) / decimal.Decimal(1e8)
             # Spend to the same number of outputs as inputs, so we can leave
-            # the amounts unchanged and avoid rounding errors.
+            # the amounts unchanged and avoid rounding errors. This also ensures
+            # the number of sigops == number of sigchecks.
             #
             # NOTE: There will be 1 sigop per output (which equals the number
             # of inputs now).  We need this randomization to ensure the
             # numbers are properly following the transactions in the block
             # template metadata
             addr = ""
             for _ in range(len(inputs)):
                 addr = mining_node.getnewaddress()
                 output = {
                     # 50 BCH per coinbase
                     addr: decimal.Decimal(50)
                 }
                 outputs.update(output)
 
             # Take the fee off the last output to avoid rounding errors we
             # need the exact fee later for assertions
             outputs[addr] -= fee
 
             rawtx = mining_node.createrawtransaction(inputs, outputs)
             signedtx = mining_node.signrawtransactionwithwallet(rawtx)
             txid = mining_node.sendrawtransaction(signedtx['hex'])
             # number of outputs is the same as the number of sigops in this
             # case
             transactions.update({txid: {'fee': fee, 'sigops': len(outputs)}})
 
         tmpl = mining_node.getblocktemplate()
         assert 'proposal' in tmpl['capabilities']
         assert 'coinbasetxn' not in tmpl
 
         # Check the template transaction metadata and ordering
         last_txid = 0
         for txn in tmpl['transactions'][1:]:
             txid = txn['txid']
             txnMetadata = transactions[txid]
             expectedFeeSats = int(txnMetadata['fee'] * 10**8)
             expectedSigOps = txnMetadata['sigops']
 
             txid_decoded = int(txid, 16)
 
             # Assert we got the expected metadata
             assert expectedFeeSats == txn['fee']
             assert expectedSigOps == txn['sigops']
             # Assert transaction ids are in order
             assert last_txid == 0 or last_txid < txid_decoded
             last_txid = txid_decoded
 
 
 if __name__ == '__main__':
     CTORMiningTest().main()
diff --git a/test/functional/test_framework/cdefs.py b/test/functional/test_framework/cdefs.py
index 19947734f2..ac457686c2 100644
--- a/test/functional/test_framework/cdefs.py
+++ b/test/functional/test_framework/cdefs.py
@@ -1,99 +1,105 @@
 #!/usr/bin/env python3
 # Copyright (c) 2017 The Bitcoin developers
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """
 Imports some application default values from source files outside the test
 framework, and defines equivalents of consensus parameters for the test
 framework.
 """
 
 import os
 import re
 
 
 def get_srcdir():
     """
     Try to find out the base folder containing the 'src' folder.
     If SRCDIR is set it does a sanity check and returns that.
     Otherwise it goes on a search and rescue mission.
 
     Returns None if it cannot find a suitable folder.
     """
     def contains_src(path_to_check):
         if not path_to_check:
             return False
         else:
             cand_path = os.path.join(path_to_check, 'src')
             return os.path.exists(cand_path) and os.path.isdir(cand_path)
 
     srcdir = os.environ.get('SRCDIR', '')
     if contains_src(srcdir):
         return srcdir
 
     # Try to work it based out on main module
     import sys
     mainmod = sys.modules['__main__']
     mainmod_path = getattr(mainmod, '__file__', '')
     if mainmod_path and mainmod_path.endswith('.py'):
         maybe_top = mainmod_path
         while maybe_top != '/':
             maybe_top = os.path.abspath(os.path.dirname(maybe_top))
             if contains_src(maybe_top):
                 return maybe_top
 
     # No luck, give up.
     return None
 
 
 # Slurp in consensus.h contents
 _consensus_h_fh = open(os.path.join(get_srcdir(), 'src', 'consensus',
                                     'consensus.h'), 'rt', encoding='utf-8')
 _consensus_h_contents = _consensus_h_fh.read()
 _consensus_h_fh.close()
 
 # This constant is currently needed to evaluate some that are formulas
 ONE_MEGABYTE = 1000000
 
 # Extract relevant default values parameters
 
 # The maximum allowed block size before the fork
 LEGACY_MAX_BLOCK_SIZE = ONE_MEGABYTE
 
 # Default setting for maximum allowed size for a block, in bytes
 DEFAULT_MAX_BLOCK_SIZE = eval(
     re.search(r'DEFAULT_MAX_BLOCK_SIZE = (.+);',
               _consensus_h_contents).group(1))
 
 # The following consensus parameters should not be automatically imported.
 # They *should* cause test failures if application code is changed in ways
 # that violate current consensus.
 
 # The maximum allowed number of signature check operations per MB in a block
 # (network rule)
 MAX_BLOCK_SIGOPS_PER_MB = 20000
 
 # The maximum allowed number of signature check operations per transaction
 # (network rule)
 MAX_TX_SIGOPS_COUNT = 20000
 
+
+# The minimum number of max_block_size bytes required per executed signature
+# check operation in a block. I.e. maximum_block_sigchecks = maximum_block_size
+# / BLOCK_MAXBYTES_MAXSIGCHECKS_RATIO (network rule).
+BLOCK_MAXBYTES_MAXSIGCHECKS_RATIO = 141
+
 # The maximum number of sigops we're willing to relay/mine in a single tx
 # (policy.h constant)
 MAX_STANDARD_TX_SIGOPS = MAX_TX_SIGOPS_COUNT // 5
 
 # Coinbase transaction outputs can only be spent after this number of new
 # blocks (network rule)
 COINBASE_MATURITY = 100
 
 # Minimum size a transaction can have.
 MIN_TX_SIZE = 100
 
 # Maximum bytes in a TxOut pubkey script
 MAX_TXOUT_PUBKEY_SCRIPT = 10000
 
 if __name__ == "__main__":
     # Output values if run standalone to verify
     print("DEFAULT_MAX_BLOCK_SIZE = {} (bytes)".format(DEFAULT_MAX_BLOCK_SIZE))
     print("MAX_BLOCK_SIGOPS_PER_MB = {} (sigops)".format(MAX_BLOCK_SIGOPS_PER_MB))
     print("MAX_TX_SIGOPS_COUNT = {} (sigops)".format(MAX_TX_SIGOPS_COUNT))
     print("COINBASE_MATURITY = {} (blocks)".format(COINBASE_MATURITY))