diff --git a/src/test/coins_tests.cpp b/src/test/coins_tests.cpp
index 04a7f5f00..62dd6ccb0 100644
--- a/src/test/coins_tests.cpp
+++ b/src/test/coins_tests.cpp
@@ -1,918 +1,920 @@
 // Copyright (c) 2014-2019 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 <coins.h>
 
+#include <attributes.h>
 #include <clientversion.h>
 #include <script/standard.h>
 #include <streams.h>
 #include <undo.h>
 #include <util/strencodings.h>
 
 #include <test/util/setup_common.h>
 
 #include <boost/test/unit_test.hpp>
 
 #include <map>
 #include <vector>
 
 void UpdateCoins(CCoinsViewCache &inputs, const CTransaction &tx,
                  CTxUndo &txundo, int nHeight);
 
 namespace {
 
 //! equality test
 bool operator==(const Coin &a, const Coin &b) {
     // Empty Coin objects are always equal.
     if (a.IsSpent() && b.IsSpent()) {
         return true;
     }
 
     return a.IsCoinBase() == b.IsCoinBase() && a.GetHeight() == b.GetHeight() &&
            a.GetTxOut() == b.GetTxOut();
 }
 
 class CCoinsViewTest : public CCoinsView {
     BlockHash hashBestBlock_;
     std::map<COutPoint, Coin> map_;
 
 public:
-    bool GetCoin(const COutPoint &outpoint, Coin &coin) const override {
+    NODISCARD bool GetCoin(const COutPoint &outpoint,
+                           Coin &coin) const override {
         std::map<COutPoint, Coin>::const_iterator it = map_.find(outpoint);
         if (it == map_.end()) {
             return false;
         }
         coin = it->second;
         if (coin.IsSpent() && InsecureRandBool() == 0) {
             // Randomly return false in case of an empty entry.
             return false;
         }
         return true;
     }
 
     BlockHash GetBestBlock() const override { return hashBestBlock_; }
 
     bool BatchWrite(CCoinsMap &mapCoins, const BlockHash &hashBlock) override {
         for (CCoinsMap::iterator it = mapCoins.begin(); it != mapCoins.end();) {
             if (it->second.flags & CCoinsCacheEntry::DIRTY) {
                 // Same optimization used in CCoinsViewDB is to only write dirty
                 // entries.
                 map_[it->first] = it->second.coin;
                 if (it->second.coin.IsSpent() && InsecureRandRange(3) == 0) {
                     // Randomly delete empty entries on write.
                     map_.erase(it->first);
                 }
             }
             mapCoins.erase(it++);
         }
         if (!hashBlock.IsNull()) {
             hashBestBlock_ = hashBlock;
         }
         return true;
     }
 };
 
 class CCoinsViewCacheTest : public CCoinsViewCache {
 public:
     explicit CCoinsViewCacheTest(CCoinsView *_base) : CCoinsViewCache(_base) {}
 
     void SelfTest() const {
         // Manually recompute the dynamic usage of the whole data, and compare
         // it.
         size_t ret = memusage::DynamicUsage(cacheCoins);
         size_t count = 0;
         for (const auto &entry : cacheCoins) {
             ret += entry.second.coin.DynamicMemoryUsage();
             count++;
         }
         BOOST_CHECK_EQUAL(GetCacheSize(), count);
         BOOST_CHECK_EQUAL(DynamicMemoryUsage(), ret);
     }
 
     CCoinsMap &map() const { return cacheCoins; }
     size_t &usage() const { return cachedCoinsUsage; }
 };
 } // namespace
 
 BOOST_FIXTURE_TEST_SUITE(coins_tests, BasicTestingSetup)
 
 static const unsigned int NUM_SIMULATION_ITERATIONS = 40000;
 
 // This is a large randomized insert/remove simulation test on a variable-size
 // stack of caches on top of CCoinsViewTest.
 //
 // It will randomly create/update/delete Coin entries to a tip of caches, with
 // txids picked from a limited list of random 256-bit hashes. Occasionally, a
 // new tip is added to the stack of caches, or the tip is flushed and removed.
 //
 // During the process, booleans are kept to make sure that the randomized
 // operation hits all branches.
 BOOST_AUTO_TEST_CASE(coins_cache_simulation_test) {
     // Various coverage trackers.
     bool removed_all_caches = false;
     bool reached_4_caches = false;
     bool added_an_entry = false;
     bool added_an_unspendable_entry = false;
     bool removed_an_entry = false;
     bool updated_an_entry = false;
     bool found_an_entry = false;
     bool missed_an_entry = false;
     bool uncached_an_entry = false;
 
     // A simple map to track what we expect the cache stack to represent.
     std::map<COutPoint, Coin> result;
 
     // The cache stack.
     // A CCoinsViewTest at the bottom.
     CCoinsViewTest base;
     // A stack of CCoinsViewCaches on top.
     std::vector<CCoinsViewCacheTest *> stack;
     // Start with one cache.
     stack.push_back(new CCoinsViewCacheTest(&base));
 
     // Use a limited set of random transaction ids, so we do test overwriting
     // entries.
     std::vector<TxId> txids;
     txids.resize(NUM_SIMULATION_ITERATIONS / 8);
     for (size_t i = 0; i < txids.size(); i++) {
         txids[i] = TxId(InsecureRand256());
     }
 
     for (unsigned int i = 0; i < NUM_SIMULATION_ITERATIONS; i++) {
         // Do a random modification.
         {
             // txid we're going to modify in this iteration.
             const TxId txid = txids[InsecureRandRange(txids.size())];
             Coin &coin = result[COutPoint(txid, 0)];
             // Determine whether to test HaveCoin before or after Access* (or
             // both). As these functions can influence each other's behaviour by
             // pulling things into the cache, all combinations are tested.
             bool test_havecoin_before = InsecureRandBits(2) == 0;
             bool test_havecoin_after = InsecureRandBits(2) == 0;
 
             bool result_havecoin =
                 test_havecoin_before
                     ? stack.back()->HaveCoin(COutPoint(txid, 0))
                     : false;
             const Coin &entry =
                 (InsecureRandRange(500) == 0)
                     ? AccessByTxid(*stack.back(), txid)
                     : stack.back()->AccessCoin(COutPoint(txid, 0));
             BOOST_CHECK(coin == entry);
             BOOST_CHECK(!test_havecoin_before ||
                         result_havecoin == !entry.IsSpent());
 
             if (test_havecoin_after) {
                 bool ret = stack.back()->HaveCoin(COutPoint(txid, 0));
                 BOOST_CHECK(ret == !entry.IsSpent());
             }
 
             if (InsecureRandRange(5) == 0 || coin.IsSpent()) {
                 CTxOut txout;
                 txout.nValue = int64_t(InsecureRand32()) * SATOSHI;
                 if (InsecureRandRange(16) == 0 && coin.IsSpent()) {
                     txout.scriptPubKey.assign(1 + InsecureRandBits(6),
                                               OP_RETURN);
                     BOOST_CHECK(txout.scriptPubKey.IsUnspendable());
                     added_an_unspendable_entry = true;
                 } else {
                     // Random sizes so we can test memory usage accounting
                     txout.scriptPubKey.assign(InsecureRandBits(6), 0);
                     (coin.IsSpent() ? added_an_entry : updated_an_entry) = true;
                     coin = Coin(txout, 1, false);
                 }
 
                 Coin newcoin(txout, 1, false);
                 stack.back()->AddCoin(COutPoint(txid, 0), newcoin,
                                       !coin.IsSpent() || InsecureRand32() & 1);
             } else {
                 removed_an_entry = true;
                 coin.Clear();
                 BOOST_CHECK(stack.back()->SpendCoin(COutPoint(txid, 0)));
             }
         }
 
         // One every 10 iterations, remove a random entry from the cache
         if (InsecureRandRange(10) == 0) {
             COutPoint out(txids[InsecureRand32() % txids.size()], 0);
             int cacheid = InsecureRand32() % stack.size();
             stack[cacheid]->Uncache(out);
             uncached_an_entry |= !stack[cacheid]->HaveCoinInCache(out);
         }
 
         // Once every 1000 iterations and at the end, verify the full cache.
         if (InsecureRandRange(1000) == 1 ||
             i == NUM_SIMULATION_ITERATIONS - 1) {
             for (const auto &entry : result) {
                 bool have = stack.back()->HaveCoin(entry.first);
                 const Coin &coin = stack.back()->AccessCoin(entry.first);
                 BOOST_CHECK(have == !coin.IsSpent());
                 BOOST_CHECK(coin == entry.second);
                 if (coin.IsSpent()) {
                     missed_an_entry = true;
                 } else {
                     BOOST_CHECK(stack.back()->HaveCoinInCache(entry.first));
                     found_an_entry = true;
                 }
             }
             for (const CCoinsViewCacheTest *test : stack) {
                 test->SelfTest();
             }
         }
 
         // Every 100 iterations, flush an intermediate cache
         if (InsecureRandRange(100) == 0) {
             if (stack.size() > 1 && InsecureRandBool() == 0) {
                 unsigned int flushIndex = InsecureRandRange(stack.size() - 1);
                 BOOST_CHECK(stack[flushIndex]->Flush());
             }
         }
         if (InsecureRandRange(100) == 0) {
             // Every 100 iterations, change the cache stack.
             if (stack.size() > 0 && InsecureRandBool() == 0) {
                 // Remove the top cache
                 BOOST_CHECK(stack.back()->Flush());
                 delete stack.back();
                 stack.pop_back();
             }
             if (stack.size() == 0 || (stack.size() < 4 && InsecureRandBool())) {
                 // Add a new cache
                 CCoinsView *tip = &base;
                 if (stack.size() > 0) {
                     tip = stack.back();
                 } else {
                     removed_all_caches = true;
                 }
                 stack.push_back(new CCoinsViewCacheTest(tip));
                 if (stack.size() == 4) {
                     reached_4_caches = true;
                 }
             }
         }
     }
 
     // Clean up the stack.
     while (stack.size() > 0) {
         delete stack.back();
         stack.pop_back();
     }
 
     // Verify coverage.
     BOOST_CHECK(removed_all_caches);
     BOOST_CHECK(reached_4_caches);
     BOOST_CHECK(added_an_entry);
     BOOST_CHECK(added_an_unspendable_entry);
     BOOST_CHECK(removed_an_entry);
     BOOST_CHECK(updated_an_entry);
     BOOST_CHECK(found_an_entry);
     BOOST_CHECK(missed_an_entry);
     BOOST_CHECK(uncached_an_entry);
 }
 
 // Store of all necessary tx and undo data for next test
 typedef std::map<COutPoint, std::tuple<CTransaction, CTxUndo, Coin>> UtxoData;
 UtxoData utxoData;
 
 UtxoData::iterator FindRandomFrom(const std::set<COutPoint> &utxoSet) {
     assert(utxoSet.size());
     auto utxoSetIt = utxoSet.lower_bound(COutPoint(TxId(InsecureRand256()), 0));
     if (utxoSetIt == utxoSet.end()) {
         utxoSetIt = utxoSet.begin();
     }
     auto utxoDataIt = utxoData.find(*utxoSetIt);
     assert(utxoDataIt != utxoData.end());
     return utxoDataIt;
 }
 
 // This test is similar to the previous test except the emphasis is on testing
 // the functionality of UpdateCoins random txs are created and UpdateCoins is
 // used to update the cache stack. In particular it is tested that spending a
 // duplicate coinbase tx has the expected effect (the other duplicate is
 // overwritten at all cache levels)
 BOOST_AUTO_TEST_CASE(updatecoins_simulation_test) {
     SeedInsecureRand(/* deterministic */ true);
     g_mock_deterministic_tests = true;
 
     bool spent_a_duplicate_coinbase = false;
     // A simple map to track what we expect the cache stack to represent.
     std::map<COutPoint, Coin> result;
 
     // The cache stack.
     // A CCoinsViewTest at the bottom.
     CCoinsViewTest base;
     // A stack of CCoinsViewCaches on top.
     std::vector<CCoinsViewCacheTest *> stack;
     // Start with one cache.
     stack.push_back(new CCoinsViewCacheTest(&base));
 
     // Track the txids we've used in various sets
     std::set<COutPoint> coinbase_coins;
     std::set<COutPoint> disconnected_coins;
     std::set<COutPoint> duplicate_coins;
     std::set<COutPoint> utxoset;
 
     for (int64_t i = 0; i < NUM_SIMULATION_ITERATIONS; i++) {
         uint32_t randiter = InsecureRand32();
 
         // 19/20 txs add a new transaction
         if (randiter % 20 < 19) {
             CMutableTransaction tx;
             tx.vin.resize(1);
             tx.vout.resize(1);
             // Keep txs unique unless intended to duplicate.
             tx.vout[0].nValue = i * SATOSHI;
             // Random sizes so we can test memory usage accounting
             tx.vout[0].scriptPubKey.assign(InsecureRand32() & 0x3F, 0);
             unsigned int height = InsecureRand32();
             Coin old_coin;
 
             // 2/20 times create a new coinbase
             if (randiter % 20 < 2 || coinbase_coins.size() < 10) {
                 // 1/10 of those times create a duplicate coinbase
                 if (InsecureRandRange(10) == 0 && coinbase_coins.size()) {
                     auto utxod = FindRandomFrom(coinbase_coins);
                     // Reuse the exact same coinbase
                     tx = CMutableTransaction{std::get<0>(utxod->second)};
                     // shouldn't be available for reconnection if it's been
                     // duplicated
                     disconnected_coins.erase(utxod->first);
 
                     duplicate_coins.insert(utxod->first);
                 } else {
                     coinbase_coins.insert(COutPoint(tx.GetId(), 0));
                 }
                 assert(CTransaction(tx).IsCoinBase());
             }
 
             // 17/20 times reconnect previous or add a regular tx
             else {
                 COutPoint prevout;
                 // 1/20 times reconnect a previously disconnected tx
                 if (randiter % 20 == 2 && disconnected_coins.size()) {
                     auto utxod = FindRandomFrom(disconnected_coins);
                     tx = CMutableTransaction{std::get<0>(utxod->second)};
                     prevout = tx.vin[0].prevout;
                     if (!CTransaction(tx).IsCoinBase() &&
                         !utxoset.count(prevout)) {
                         disconnected_coins.erase(utxod->first);
                         continue;
                     }
 
                     // If this tx is already IN the UTXO, then it must be a
                     // coinbase, and it must be a duplicate
                     if (utxoset.count(utxod->first)) {
                         assert(CTransaction(tx).IsCoinBase());
                         assert(duplicate_coins.count(utxod->first));
                     }
                     disconnected_coins.erase(utxod->first);
                 }
 
                 // 16/20 times create a regular tx
                 else {
                     auto utxod = FindRandomFrom(utxoset);
                     prevout = utxod->first;
 
                     // Construct the tx to spend the coins of prevouthash
                     tx.vin[0].prevout = COutPoint(prevout.GetTxId(), 0);
                     assert(!CTransaction(tx).IsCoinBase());
                 }
 
                 // In this simple test coins only have two states, spent or
                 // unspent, save the unspent state to restore
                 old_coin = result[prevout];
                 // Update the expected result of prevouthash to know these coins
                 // are spent
                 result[prevout].Clear();
 
                 utxoset.erase(prevout);
 
                 // The test is designed to ensure spending a duplicate coinbase
                 // will work properly if that ever happens and not resurrect the
                 // previously overwritten coinbase
                 if (duplicate_coins.count(prevout)) {
                     spent_a_duplicate_coinbase = true;
                 }
             }
             // Update the expected result to know about the new output coins
             assert(tx.vout.size() == 1);
             const COutPoint outpoint(tx.GetId(), 0);
             result[outpoint] =
                 Coin(tx.vout[0], height, CTransaction(tx).IsCoinBase());
 
             // Call UpdateCoins on the top cache
             CTxUndo undo;
             UpdateCoins(*(stack.back()), CTransaction(tx), undo, height);
 
             // Update the utxo set for future spends
             utxoset.insert(outpoint);
 
             // Track this tx and undo info to use later
             utxoData.emplace(outpoint,
                              std::make_tuple(CTransaction(tx), undo, old_coin));
         }
 
         // 1/20 times undo a previous transaction
         else if (utxoset.size()) {
             auto utxod = FindRandomFrom(utxoset);
 
             CTransaction &tx = std::get<0>(utxod->second);
             CTxUndo &undo = std::get<1>(utxod->second);
             Coin &orig_coin = std::get<2>(utxod->second);
 
             // Update the expected result
             // Remove new outputs
             result[utxod->first].Clear();
             // If not coinbase restore prevout
             if (!tx.IsCoinBase()) {
                 result[tx.vin[0].prevout] = orig_coin;
             }
 
             // Disconnect the tx from the current UTXO
             // See code in DisconnectBlock
             // remove outputs
             BOOST_CHECK(stack.back()->SpendCoin(utxod->first));
 
             // restore inputs
             if (!tx.IsCoinBase()) {
                 const COutPoint &out = tx.vin[0].prevout;
                 UndoCoinSpend(undo.vprevout[0], *(stack.back()), out);
             }
 
             // Store as a candidate for reconnection
             disconnected_coins.insert(utxod->first);
 
             // Update the utxoset
             utxoset.erase(utxod->first);
             if (!tx.IsCoinBase()) {
                 utxoset.insert(tx.vin[0].prevout);
             }
         }
 
         // Once every 1000 iterations and at the end, verify the full cache.
         if (InsecureRandRange(1000) == 1 ||
             i == NUM_SIMULATION_ITERATIONS - 1) {
             for (const auto &entry : result) {
                 bool have = stack.back()->HaveCoin(entry.first);
                 const Coin &coin = stack.back()->AccessCoin(entry.first);
                 BOOST_CHECK(have == !coin.IsSpent());
                 BOOST_CHECK(coin == entry.second);
             }
         }
 
         // One every 10 iterations, remove a random entry from the cache
         if (utxoset.size() > 1 && InsecureRandRange(30) == 0) {
             stack[InsecureRand32() % stack.size()]->Uncache(
                 FindRandomFrom(utxoset)->first);
         }
         if (disconnected_coins.size() > 1 && InsecureRandRange(30) == 0) {
             stack[InsecureRand32() % stack.size()]->Uncache(
                 FindRandomFrom(disconnected_coins)->first);
         }
         if (duplicate_coins.size() > 1 && InsecureRandRange(30) == 0) {
             stack[InsecureRand32() % stack.size()]->Uncache(
                 FindRandomFrom(duplicate_coins)->first);
         }
 
         if (InsecureRandRange(100) == 0) {
             // Every 100 iterations, flush an intermediate cache
             if (stack.size() > 1 && InsecureRandBool() == 0) {
                 unsigned int flushIndex = InsecureRandRange(stack.size() - 1);
                 BOOST_CHECK(stack[flushIndex]->Flush());
             }
         }
         if (InsecureRandRange(100) == 0) {
             // Every 100 iterations, change the cache stack.
             if (stack.size() > 0 && InsecureRandBool() == 0) {
                 BOOST_CHECK(stack.back()->Flush());
                 delete stack.back();
                 stack.pop_back();
             }
             if (stack.size() == 0 || (stack.size() < 4 && InsecureRandBool())) {
                 CCoinsView *tip = &base;
                 if (stack.size() > 0) {
                     tip = stack.back();
                 }
                 stack.push_back(new CCoinsViewCacheTest(tip));
             }
         }
     }
 
     // Clean up the stack.
     while (stack.size() > 0) {
         delete stack.back();
         stack.pop_back();
     }
 
     // Verify coverage.
     BOOST_CHECK(spent_a_duplicate_coinbase);
 
     g_mock_deterministic_tests = false;
 }
 
 BOOST_AUTO_TEST_CASE(coin_serialization) {
     // Good example
     CDataStream ss1(
         ParseHex("97f23c835800816115944e077fe7c803cfa57f29b36bf87c1d35"),
         SER_DISK, CLIENT_VERSION);
     Coin c1;
     ss1 >> c1;
     BOOST_CHECK_EQUAL(c1.IsCoinBase(), false);
     BOOST_CHECK_EQUAL(c1.GetHeight(), 203998U);
     BOOST_CHECK_EQUAL(c1.GetTxOut().nValue, int64_t(60000000000) * SATOSHI);
     BOOST_CHECK_EQUAL(HexStr(c1.GetTxOut().scriptPubKey),
                       HexStr(GetScriptForDestination(PKHash(uint160(ParseHex(
                           "816115944e077fe7c803cfa57f29b36bf87c1d35"))))));
 
     // Good example
     CDataStream ss2(
         ParseHex("8ddf77bbd123008c988f1a4a4de2161e0f50aac7f17e7f9555caa4"),
         SER_DISK, CLIENT_VERSION);
     Coin c2;
     ss2 >> c2;
     BOOST_CHECK_EQUAL(c2.IsCoinBase(), true);
     BOOST_CHECK_EQUAL(c2.GetHeight(), 120891U);
     BOOST_CHECK_EQUAL(c2.GetTxOut().nValue, 110397 * SATOSHI);
     BOOST_CHECK_EQUAL(HexStr(c2.GetTxOut().scriptPubKey),
                       HexStr(GetScriptForDestination(PKHash(uint160(ParseHex(
                           "8c988f1a4a4de2161e0f50aac7f17e7f9555caa4"))))));
 
     // Smallest possible example
     CDataStream ss3(ParseHex("000006"), SER_DISK, CLIENT_VERSION);
     Coin c3;
     ss3 >> c3;
     BOOST_CHECK_EQUAL(c3.IsCoinBase(), false);
     BOOST_CHECK_EQUAL(c3.GetHeight(), 0U);
     BOOST_CHECK_EQUAL(c3.GetTxOut().nValue, Amount::zero());
     BOOST_CHECK_EQUAL(c3.GetTxOut().scriptPubKey.size(), 0U);
 
     // scriptPubKey that ends beyond the end of the stream
     CDataStream ss4(ParseHex("000007"), SER_DISK, CLIENT_VERSION);
     try {
         Coin c4;
         ss4 >> c4;
         BOOST_CHECK_MESSAGE(false, "We should have thrown");
     } catch (const std::ios_base::failure &) {
     }
 
     // Very large scriptPubKey (3*10^9 bytes) past the end of the stream
     CDataStream tmp(SER_DISK, CLIENT_VERSION);
     uint64_t x = 3000000000ULL;
     tmp << VARINT(x);
     BOOST_CHECK_EQUAL(HexStr(tmp.begin(), tmp.end()), "8a95c0bb00");
     CDataStream ss5(ParseHex("00008a95c0bb00"), SER_DISK, CLIENT_VERSION);
     try {
         Coin c5;
         ss5 >> c5;
         BOOST_CHECK_MESSAGE(false, "We should have thrown");
     } catch (const std::ios_base::failure &) {
     }
 }
 
 static const COutPoint OUTPOINT;
 static const Amount PRUNED(-1 * SATOSHI);
 static const Amount ABSENT(-2 * SATOSHI);
 static const Amount FAIL(-3 * SATOSHI);
 static const Amount VALUE1(100 * SATOSHI);
 static const Amount VALUE2(200 * SATOSHI);
 static const Amount VALUE3(300 * SATOSHI);
 static const char DIRTY = CCoinsCacheEntry::DIRTY;
 static const char FRESH = CCoinsCacheEntry::FRESH;
 static const char NO_ENTRY = -1;
 
 static const auto FLAGS = {char(0), FRESH, DIRTY, char(DIRTY | FRESH)};
 static const auto CLEAN_FLAGS = {char(0), FRESH};
 static const auto ABSENT_FLAGS = {NO_ENTRY};
 
 static void SetCoinValue(const Amount value, Coin &coin) {
     assert(value != ABSENT);
     coin.Clear();
     assert(coin.IsSpent());
     if (value != PRUNED) {
         CTxOut out;
         out.nValue = value;
         coin = Coin(std::move(out), 1, false);
         assert(!coin.IsSpent());
     }
 }
 
 static size_t InsertCoinMapEntry(CCoinsMap &map, const Amount value,
                                  char flags) {
     if (value == ABSENT) {
         assert(flags == NO_ENTRY);
         return 0;
     }
     assert(flags != NO_ENTRY);
     CCoinsCacheEntry entry;
     entry.flags = flags;
     SetCoinValue(value, entry.coin);
     auto inserted = map.emplace(OUTPOINT, std::move(entry));
     assert(inserted.second);
     return inserted.first->second.coin.DynamicMemoryUsage();
 }
 
 void GetCoinMapEntry(const CCoinsMap &map, Amount &value, char &flags) {
     auto it = map.find(OUTPOINT);
     if (it == map.end()) {
         value = ABSENT;
         flags = NO_ENTRY;
     } else {
         if (it->second.coin.IsSpent()) {
             value = PRUNED;
         } else {
             value = it->second.coin.GetTxOut().nValue;
         }
         flags = it->second.flags;
         assert(flags != NO_ENTRY);
     }
 }
 
 void WriteCoinViewEntry(CCoinsView &view, const Amount value, char flags) {
     CCoinsMap map;
     InsertCoinMapEntry(map, value, flags);
     BOOST_CHECK(view.BatchWrite(map, BlockHash()));
 }
 
 class SingleEntryCacheTest {
 public:
     SingleEntryCacheTest(const Amount base_value, const Amount cache_value,
                          char cache_flags) {
         WriteCoinViewEntry(base, base_value,
                            base_value == ABSENT ? NO_ENTRY : DIRTY);
         cache.usage() +=
             InsertCoinMapEntry(cache.map(), cache_value, cache_flags);
     }
 
     CCoinsView root;
     CCoinsViewCacheTest base{&root};
     CCoinsViewCacheTest cache{&base};
 };
 
 static void CheckAccessCoin(const Amount base_value, const Amount cache_value,
                             const Amount expected_value, char cache_flags,
                             char expected_flags) {
     SingleEntryCacheTest test(base_value, cache_value, cache_flags);
     test.cache.AccessCoin(OUTPOINT);
     test.cache.SelfTest();
 
     Amount result_value;
     char result_flags;
     GetCoinMapEntry(test.cache.map(), result_value, result_flags);
     BOOST_CHECK_EQUAL(result_value, expected_value);
     BOOST_CHECK_EQUAL(result_flags, expected_flags);
 }
 
 BOOST_AUTO_TEST_CASE(coin_access) {
     /* Check AccessCoin behavior, requesting a coin from a cache view layered on
      * top of a base view, and checking the resulting entry in the cache after
      * the access.
      *
      *               Base    Cache   Result  Cache        Result
      *               Value   Value   Value   Flags        Flags
      */
     CheckAccessCoin(ABSENT, ABSENT, ABSENT, NO_ENTRY, NO_ENTRY);
     CheckAccessCoin(ABSENT, PRUNED, PRUNED, 0, 0);
     CheckAccessCoin(ABSENT, PRUNED, PRUNED, FRESH, FRESH);
     CheckAccessCoin(ABSENT, PRUNED, PRUNED, DIRTY, DIRTY);
     CheckAccessCoin(ABSENT, PRUNED, PRUNED, DIRTY | FRESH, DIRTY | FRESH);
     CheckAccessCoin(ABSENT, VALUE2, VALUE2, 0, 0);
     CheckAccessCoin(ABSENT, VALUE2, VALUE2, FRESH, FRESH);
     CheckAccessCoin(ABSENT, VALUE2, VALUE2, DIRTY, DIRTY);
     CheckAccessCoin(ABSENT, VALUE2, VALUE2, DIRTY | FRESH, DIRTY | FRESH);
     CheckAccessCoin(PRUNED, ABSENT, ABSENT, NO_ENTRY, NO_ENTRY);
     CheckAccessCoin(PRUNED, PRUNED, PRUNED, 0, 0);
     CheckAccessCoin(PRUNED, PRUNED, PRUNED, FRESH, FRESH);
     CheckAccessCoin(PRUNED, PRUNED, PRUNED, DIRTY, DIRTY);
     CheckAccessCoin(PRUNED, PRUNED, PRUNED, DIRTY | FRESH, DIRTY | FRESH);
     CheckAccessCoin(PRUNED, VALUE2, VALUE2, 0, 0);
     CheckAccessCoin(PRUNED, VALUE2, VALUE2, FRESH, FRESH);
     CheckAccessCoin(PRUNED, VALUE2, VALUE2, DIRTY, DIRTY);
     CheckAccessCoin(PRUNED, VALUE2, VALUE2, DIRTY | FRESH, DIRTY | FRESH);
     CheckAccessCoin(VALUE1, ABSENT, VALUE1, NO_ENTRY, 0);
     CheckAccessCoin(VALUE1, PRUNED, PRUNED, 0, 0);
     CheckAccessCoin(VALUE1, PRUNED, PRUNED, FRESH, FRESH);
     CheckAccessCoin(VALUE1, PRUNED, PRUNED, DIRTY, DIRTY);
     CheckAccessCoin(VALUE1, PRUNED, PRUNED, DIRTY | FRESH, DIRTY | FRESH);
     CheckAccessCoin(VALUE1, VALUE2, VALUE2, 0, 0);
     CheckAccessCoin(VALUE1, VALUE2, VALUE2, FRESH, FRESH);
     CheckAccessCoin(VALUE1, VALUE2, VALUE2, DIRTY, DIRTY);
     CheckAccessCoin(VALUE1, VALUE2, VALUE2, DIRTY | FRESH, DIRTY | FRESH);
 }
 
 static void CheckSpendCoin(Amount base_value, Amount cache_value,
                            Amount expected_value, char cache_flags,
                            char expected_flags) {
     SingleEntryCacheTest test(base_value, cache_value, cache_flags);
     test.cache.SpendCoin(OUTPOINT);
     test.cache.SelfTest();
 
     Amount result_value;
     char result_flags;
     GetCoinMapEntry(test.cache.map(), result_value, result_flags);
     BOOST_CHECK_EQUAL(result_value, expected_value);
     BOOST_CHECK_EQUAL(result_flags, expected_flags);
 };
 
 BOOST_AUTO_TEST_CASE(coin_spend) {
     /**
      * Check SpendCoin behavior, requesting a coin from a cache view layered on
      * top of a base view, spending, and then checking the resulting entry in
      * the cache after the modification.
      *
      *              Base    Cache   Result  Cache        Result
      *              Value   Value   Value   Flags        Flags
      */
     CheckSpendCoin(ABSENT, ABSENT, ABSENT, NO_ENTRY, NO_ENTRY);
     CheckSpendCoin(ABSENT, PRUNED, PRUNED, 0, DIRTY);
     CheckSpendCoin(ABSENT, PRUNED, ABSENT, FRESH, NO_ENTRY);
     CheckSpendCoin(ABSENT, PRUNED, PRUNED, DIRTY, DIRTY);
     CheckSpendCoin(ABSENT, PRUNED, ABSENT, DIRTY | FRESH, NO_ENTRY);
     CheckSpendCoin(ABSENT, VALUE2, PRUNED, 0, DIRTY);
     CheckSpendCoin(ABSENT, VALUE2, ABSENT, FRESH, NO_ENTRY);
     CheckSpendCoin(ABSENT, VALUE2, PRUNED, DIRTY, DIRTY);
     CheckSpendCoin(ABSENT, VALUE2, ABSENT, DIRTY | FRESH, NO_ENTRY);
     CheckSpendCoin(PRUNED, ABSENT, ABSENT, NO_ENTRY, NO_ENTRY);
     CheckSpendCoin(PRUNED, PRUNED, PRUNED, 0, DIRTY);
     CheckSpendCoin(PRUNED, PRUNED, ABSENT, FRESH, NO_ENTRY);
     CheckSpendCoin(PRUNED, PRUNED, PRUNED, DIRTY, DIRTY);
     CheckSpendCoin(PRUNED, PRUNED, ABSENT, DIRTY | FRESH, NO_ENTRY);
     CheckSpendCoin(PRUNED, VALUE2, PRUNED, 0, DIRTY);
     CheckSpendCoin(PRUNED, VALUE2, ABSENT, FRESH, NO_ENTRY);
     CheckSpendCoin(PRUNED, VALUE2, PRUNED, DIRTY, DIRTY);
     CheckSpendCoin(PRUNED, VALUE2, ABSENT, DIRTY | FRESH, NO_ENTRY);
     CheckSpendCoin(VALUE1, ABSENT, PRUNED, NO_ENTRY, DIRTY);
     CheckSpendCoin(VALUE1, PRUNED, PRUNED, 0, DIRTY);
     CheckSpendCoin(VALUE1, PRUNED, ABSENT, FRESH, NO_ENTRY);
     CheckSpendCoin(VALUE1, PRUNED, PRUNED, DIRTY, DIRTY);
     CheckSpendCoin(VALUE1, PRUNED, ABSENT, DIRTY | FRESH, NO_ENTRY);
     CheckSpendCoin(VALUE1, VALUE2, PRUNED, 0, DIRTY);
     CheckSpendCoin(VALUE1, VALUE2, ABSENT, FRESH, NO_ENTRY);
     CheckSpendCoin(VALUE1, VALUE2, PRUNED, DIRTY, DIRTY);
     CheckSpendCoin(VALUE1, VALUE2, ABSENT, DIRTY | FRESH, NO_ENTRY);
 }
 
 static void CheckAddCoinBase(Amount base_value, Amount cache_value,
                              Amount modify_value, Amount expected_value,
                              char cache_flags, char expected_flags,
                              bool coinbase) {
     SingleEntryCacheTest test(base_value, cache_value, cache_flags);
 
     Amount result_value;
     char result_flags;
     try {
         CTxOut output;
         output.nValue = modify_value;
         test.cache.AddCoin(OUTPOINT, Coin(std::move(output), 1, coinbase),
                            coinbase);
         test.cache.SelfTest();
         GetCoinMapEntry(test.cache.map(), result_value, result_flags);
     } catch (std::logic_error &) {
         result_value = FAIL;
         result_flags = NO_ENTRY;
     }
 
     BOOST_CHECK_EQUAL(result_value, expected_value);
     BOOST_CHECK_EQUAL(result_flags, expected_flags);
 }
 
 // Simple wrapper for CheckAddCoinBase function above that loops through
 // different possible base_values, making sure each one gives the same results.
 // This wrapper lets the coin_add test below be shorter and less repetitive,
 // while still verifying that the CoinsViewCache::AddCoin implementation ignores
 // base values.
 template <typename... Args> static void CheckAddCoin(Args &&... args) {
     for (const Amount &base_value : {ABSENT, PRUNED, VALUE1}) {
         CheckAddCoinBase(base_value, std::forward<Args>(args)...);
     }
 }
 
 BOOST_AUTO_TEST_CASE(coin_add) {
     /**
      * Check AddCoin behavior, requesting a new coin from a cache view, writing
      * a modification to the coin, and then checking the resulting entry in the
      * cache after the modification. Verify behavior with the with the AddCoin
      * potential_overwrite argument set to false, and to true.
      *
      * Cache   Write   Result  Cache        Result       potential_overwrite
      * Value   Value   Value   Flags        Flags
      */
     CheckAddCoin(ABSENT, VALUE3, VALUE3, NO_ENTRY, DIRTY | FRESH, false);
     CheckAddCoin(ABSENT, VALUE3, VALUE3, NO_ENTRY, DIRTY, true);
     CheckAddCoin(PRUNED, VALUE3, VALUE3, 0, DIRTY | FRESH, false);
     CheckAddCoin(PRUNED, VALUE3, VALUE3, 0, DIRTY, true);
     CheckAddCoin(PRUNED, VALUE3, VALUE3, FRESH, DIRTY | FRESH, false);
     CheckAddCoin(PRUNED, VALUE3, VALUE3, FRESH, DIRTY | FRESH, true);
     CheckAddCoin(PRUNED, VALUE3, VALUE3, DIRTY, DIRTY, false);
     CheckAddCoin(PRUNED, VALUE3, VALUE3, DIRTY, DIRTY, true);
     CheckAddCoin(PRUNED, VALUE3, VALUE3, DIRTY | FRESH, DIRTY | FRESH, false);
     CheckAddCoin(PRUNED, VALUE3, VALUE3, DIRTY | FRESH, DIRTY | FRESH, true);
     CheckAddCoin(VALUE2, VALUE3, FAIL, 0, NO_ENTRY, false);
     CheckAddCoin(VALUE2, VALUE3, VALUE3, 0, DIRTY, true);
     CheckAddCoin(VALUE2, VALUE3, FAIL, FRESH, NO_ENTRY, false);
     CheckAddCoin(VALUE2, VALUE3, VALUE3, FRESH, DIRTY | FRESH, true);
     CheckAddCoin(VALUE2, VALUE3, FAIL, DIRTY, NO_ENTRY, false);
     CheckAddCoin(VALUE2, VALUE3, VALUE3, DIRTY, DIRTY, true);
     CheckAddCoin(VALUE2, VALUE3, FAIL, DIRTY | FRESH, NO_ENTRY, false);
     CheckAddCoin(VALUE2, VALUE3, VALUE3, DIRTY | FRESH, DIRTY | FRESH, true);
 }
 
 void CheckWriteCoin(Amount parent_value, Amount child_value,
                     Amount expected_value, char parent_flags, char child_flags,
                     char expected_flags) {
     SingleEntryCacheTest test(ABSENT, parent_value, parent_flags);
 
     Amount result_value;
     char result_flags;
     try {
         WriteCoinViewEntry(test.cache, child_value, child_flags);
         test.cache.SelfTest();
         GetCoinMapEntry(test.cache.map(), result_value, result_flags);
     } catch (std::logic_error &) {
         result_value = FAIL;
         result_flags = NO_ENTRY;
     }
 
     BOOST_CHECK_EQUAL(result_value, expected_value);
     BOOST_CHECK_EQUAL(result_flags, expected_flags);
 }
 
 BOOST_AUTO_TEST_CASE(coin_write) {
     /* Check BatchWrite behavior, flushing one entry from a child cache to a
      * parent cache, and checking the resulting entry in the parent cache
      * after the write.
      *
      *              Parent  Child   Result  Parent       Child        Result
      *              Value   Value   Value   Flags        Flags        Flags
      */
     CheckWriteCoin(ABSENT, ABSENT, ABSENT, NO_ENTRY, NO_ENTRY, NO_ENTRY);
     CheckWriteCoin(ABSENT, PRUNED, PRUNED, NO_ENTRY, DIRTY, DIRTY);
     CheckWriteCoin(ABSENT, PRUNED, ABSENT, NO_ENTRY, DIRTY | FRESH, NO_ENTRY);
     CheckWriteCoin(ABSENT, VALUE2, VALUE2, NO_ENTRY, DIRTY, DIRTY);
     CheckWriteCoin(ABSENT, VALUE2, VALUE2, NO_ENTRY, DIRTY | FRESH,
                    DIRTY | FRESH);
     CheckWriteCoin(PRUNED, ABSENT, PRUNED, 0, NO_ENTRY, 0);
     CheckWriteCoin(PRUNED, ABSENT, PRUNED, FRESH, NO_ENTRY, FRESH);
     CheckWriteCoin(PRUNED, ABSENT, PRUNED, DIRTY, NO_ENTRY, DIRTY);
     CheckWriteCoin(PRUNED, ABSENT, PRUNED, DIRTY | FRESH, NO_ENTRY,
                    DIRTY | FRESH);
     CheckWriteCoin(PRUNED, PRUNED, PRUNED, 0, DIRTY, DIRTY);
     CheckWriteCoin(PRUNED, PRUNED, PRUNED, 0, DIRTY | FRESH, DIRTY);
     CheckWriteCoin(PRUNED, PRUNED, ABSENT, FRESH, DIRTY, NO_ENTRY);
     CheckWriteCoin(PRUNED, PRUNED, ABSENT, FRESH, DIRTY | FRESH, NO_ENTRY);
     CheckWriteCoin(PRUNED, PRUNED, PRUNED, DIRTY, DIRTY, DIRTY);
     CheckWriteCoin(PRUNED, PRUNED, PRUNED, DIRTY, DIRTY | FRESH, DIRTY);
     CheckWriteCoin(PRUNED, PRUNED, ABSENT, DIRTY | FRESH, DIRTY, NO_ENTRY);
     CheckWriteCoin(PRUNED, PRUNED, ABSENT, DIRTY | FRESH, DIRTY | FRESH,
                    NO_ENTRY);
     CheckWriteCoin(PRUNED, VALUE2, VALUE2, 0, DIRTY, DIRTY);
     CheckWriteCoin(PRUNED, VALUE2, VALUE2, 0, DIRTY | FRESH, DIRTY);
     CheckWriteCoin(PRUNED, VALUE2, VALUE2, FRESH, DIRTY, DIRTY | FRESH);
     CheckWriteCoin(PRUNED, VALUE2, VALUE2, FRESH, DIRTY | FRESH, DIRTY | FRESH);
     CheckWriteCoin(PRUNED, VALUE2, VALUE2, DIRTY, DIRTY, DIRTY);
     CheckWriteCoin(PRUNED, VALUE2, VALUE2, DIRTY, DIRTY | FRESH, DIRTY);
     CheckWriteCoin(PRUNED, VALUE2, VALUE2, DIRTY | FRESH, DIRTY, DIRTY | FRESH);
     CheckWriteCoin(PRUNED, VALUE2, VALUE2, DIRTY | FRESH, DIRTY | FRESH,
                    DIRTY | FRESH);
     CheckWriteCoin(VALUE1, ABSENT, VALUE1, 0, NO_ENTRY, 0);
     CheckWriteCoin(VALUE1, ABSENT, VALUE1, FRESH, NO_ENTRY, FRESH);
     CheckWriteCoin(VALUE1, ABSENT, VALUE1, DIRTY, NO_ENTRY, DIRTY);
     CheckWriteCoin(VALUE1, ABSENT, VALUE1, DIRTY | FRESH, NO_ENTRY,
                    DIRTY | FRESH);
     CheckWriteCoin(VALUE1, PRUNED, PRUNED, 0, DIRTY, DIRTY);
     CheckWriteCoin(VALUE1, PRUNED, FAIL, 0, DIRTY | FRESH, NO_ENTRY);
     CheckWriteCoin(VALUE1, PRUNED, ABSENT, FRESH, DIRTY, NO_ENTRY);
     CheckWriteCoin(VALUE1, PRUNED, FAIL, FRESH, DIRTY | FRESH, NO_ENTRY);
     CheckWriteCoin(VALUE1, PRUNED, PRUNED, DIRTY, DIRTY, DIRTY);
     CheckWriteCoin(VALUE1, PRUNED, FAIL, DIRTY, DIRTY | FRESH, NO_ENTRY);
     CheckWriteCoin(VALUE1, PRUNED, ABSENT, DIRTY | FRESH, DIRTY, NO_ENTRY);
     CheckWriteCoin(VALUE1, PRUNED, FAIL, DIRTY | FRESH, DIRTY | FRESH,
                    NO_ENTRY);
     CheckWriteCoin(VALUE1, VALUE2, VALUE2, 0, DIRTY, DIRTY);
     CheckWriteCoin(VALUE1, VALUE2, FAIL, 0, DIRTY | FRESH, NO_ENTRY);
     CheckWriteCoin(VALUE1, VALUE2, VALUE2, FRESH, DIRTY, DIRTY | FRESH);
     CheckWriteCoin(VALUE1, VALUE2, FAIL, FRESH, DIRTY | FRESH, NO_ENTRY);
     CheckWriteCoin(VALUE1, VALUE2, VALUE2, DIRTY, DIRTY, DIRTY);
     CheckWriteCoin(VALUE1, VALUE2, FAIL, DIRTY, DIRTY | FRESH, NO_ENTRY);
     CheckWriteCoin(VALUE1, VALUE2, VALUE2, DIRTY | FRESH, DIRTY, DIRTY | FRESH);
     CheckWriteCoin(VALUE1, VALUE2, FAIL, DIRTY | FRESH, DIRTY | FRESH,
                    NO_ENTRY);
 
     // The checks above omit cases where the child flags are not DIRTY, since
     // they would be too repetitive (the parent cache is never updated in these
     // cases). The loop below covers these cases and makes sure the parent cache
     // is always left unchanged.
     for (const Amount &parent_value : {ABSENT, PRUNED, VALUE1}) {
         for (const Amount &child_value : {ABSENT, PRUNED, VALUE2}) {
             for (const char parent_flags :
                  parent_value == ABSENT ? ABSENT_FLAGS : FLAGS) {
                 for (const char child_flags :
                      child_value == ABSENT ? ABSENT_FLAGS : CLEAN_FLAGS) {
                     CheckWriteCoin(parent_value, child_value, parent_value,
                                    parent_flags, child_flags, parent_flags);
                 }
             }
         }
     }
 }
 
 BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/test/dbwrapper_tests.cpp b/src/test/dbwrapper_tests.cpp
index 3ad58ef49..4c8875b93 100644
--- a/src/test/dbwrapper_tests.cpp
+++ b/src/test/dbwrapper_tests.cpp
@@ -1,343 +1,343 @@
 // Copyright (c) 2012-2019 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 <dbwrapper.h>
 
 #include <uint256.h>
 
 #include <test/util/setup_common.h>
 
 #include <boost/test/unit_test.hpp>
 
 #include <memory>
 
 // Test if a string consists entirely of null characters
 static bool is_null_key(const std::vector<uint8_t> &key) {
     bool isnull = true;
 
     for (unsigned int i = 0; i < key.size(); i++) {
         isnull &= (key[i] == '\x00');
     }
 
     return isnull;
 }
 
 BOOST_FIXTURE_TEST_SUITE(dbwrapper_tests, BasicTestingSetup)
 
 BOOST_AUTO_TEST_CASE(dbwrapper) {
     // Perform tests both obfuscated and non-obfuscated.
     for (const bool obfuscate : {false, true}) {
         fs::path ph = GetDataDir() / (obfuscate ? "dbwrapper_obfuscate_true"
                                                 : "dbwrapper_obfuscate_false");
         CDBWrapper dbw(ph, (1 << 20), true, false, obfuscate);
         char key = 'k';
         uint256 in = InsecureRand256();
         uint256 res;
 
         // Ensure that we're doing real obfuscation when obfuscate=true
         BOOST_CHECK(obfuscate !=
                     is_null_key(dbwrapper_private::GetObfuscateKey(dbw)));
 
         BOOST_CHECK(dbw.Write(key, in));
         BOOST_CHECK(dbw.Read(key, res));
         BOOST_CHECK_EQUAL(res.ToString(), in.ToString());
     }
 }
 
 // Test batch operations
 BOOST_AUTO_TEST_CASE(dbwrapper_batch) {
     // Perform tests both obfuscated and non-obfuscated.
     for (const bool obfuscate : {false, true}) {
         fs::path ph =
             GetDataDir() / (obfuscate ? "dbwrapper_batch_obfuscate_true"
                                       : "dbwrapper_batch_obfuscate_false");
         CDBWrapper dbw(ph, (1 << 20), true, false, obfuscate);
 
         char key = 'i';
         uint256 in = InsecureRand256();
         char key2 = 'j';
         uint256 in2 = InsecureRand256();
         char key3 = 'k';
         uint256 in3 = InsecureRand256();
 
         uint256 res;
         CDBBatch batch(dbw);
 
         batch.Write(key, in);
         batch.Write(key2, in2);
         batch.Write(key3, in3);
 
         // Remove key3 before it's even been written
         batch.Erase(key3);
 
         BOOST_CHECK(dbw.WriteBatch(batch));
 
         BOOST_CHECK(dbw.Read(key, res));
         BOOST_CHECK_EQUAL(res.ToString(), in.ToString());
         BOOST_CHECK(dbw.Read(key2, res));
         BOOST_CHECK_EQUAL(res.ToString(), in2.ToString());
 
         // key3 should've never been written
         BOOST_CHECK(dbw.Read(key3, res) == false);
     }
 }
 
 BOOST_AUTO_TEST_CASE(dbwrapper_iterator) {
     // Perform tests both obfuscated and non-obfuscated.
     for (const bool obfuscate : {false, true}) {
         fs::path ph =
             GetDataDir() / (obfuscate ? "dbwrapper_iterator_obfuscate_true"
                                       : "dbwrapper_iterator_obfuscate_false");
         CDBWrapper dbw(ph, (1 << 20), true, false, obfuscate);
 
         // The two keys are intentionally chosen for ordering
         char key = 'j';
         uint256 in = InsecureRand256();
         BOOST_CHECK(dbw.Write(key, in));
         char key2 = 'k';
         uint256 in2 = InsecureRand256();
         BOOST_CHECK(dbw.Write(key2, in2));
 
         std::unique_ptr<CDBIterator> it(
             const_cast<CDBWrapper &>(dbw).NewIterator());
 
         // Be sure to seek past the obfuscation key (if it exists)
         it->Seek(key);
 
         char key_res;
         uint256 val_res;
 
-        it->GetKey(key_res);
-        it->GetValue(val_res);
+        BOOST_REQUIRE(it->GetKey(key_res));
+        BOOST_REQUIRE(it->GetValue(val_res));
         BOOST_CHECK_EQUAL(key_res, key);
         BOOST_CHECK_EQUAL(val_res.ToString(), in.ToString());
 
         it->Next();
 
-        it->GetKey(key_res);
-        it->GetValue(val_res);
+        BOOST_REQUIRE(it->GetKey(key_res));
+        BOOST_REQUIRE(it->GetValue(val_res));
         BOOST_CHECK_EQUAL(key_res, key2);
         BOOST_CHECK_EQUAL(val_res.ToString(), in2.ToString());
 
         it->Next();
         BOOST_CHECK_EQUAL(it->Valid(), false);
     }
 }
 
 // Test that we do not obfuscation if there is existing data.
 BOOST_AUTO_TEST_CASE(existing_data_no_obfuscate) {
     // We're going to share this fs::path between two wrappers
     fs::path ph = GetDataDir() / "existing_data_no_obfuscate";
     create_directories(ph);
 
     // Set up a non-obfuscated wrapper to write some initial data.
     std::unique_ptr<CDBWrapper> dbw =
         std::make_unique<CDBWrapper>(ph, (1 << 10), false, false, false);
     char key = 'k';
     uint256 in = InsecureRand256();
     uint256 res;
 
     BOOST_CHECK(dbw->Write(key, in));
     BOOST_CHECK(dbw->Read(key, res));
     BOOST_CHECK_EQUAL(res.ToString(), in.ToString());
 
     // Call the destructor to free leveldb LOCK
     dbw.reset();
 
     // Now, set up another wrapper that wants to obfuscate the same directory
     CDBWrapper odbw(ph, (1 << 10), false, false, true);
 
     // Check that the key/val we wrote with unobfuscated wrapper exists and
     // is readable.
     uint256 res2;
     BOOST_CHECK(odbw.Read(key, res2));
     BOOST_CHECK_EQUAL(res2.ToString(), in.ToString());
 
     // There should be existing data
     BOOST_CHECK(!odbw.IsEmpty());
     // The key should be an empty string
     BOOST_CHECK(is_null_key(dbwrapper_private::GetObfuscateKey(odbw)));
 
     uint256 in2 = InsecureRand256();
     uint256 res3;
 
     // Check that we can write successfully
     BOOST_CHECK(odbw.Write(key, in2));
     BOOST_CHECK(odbw.Read(key, res3));
     BOOST_CHECK_EQUAL(res3.ToString(), in2.ToString());
 }
 
 // Ensure that we start obfuscating during a reindex.
 BOOST_AUTO_TEST_CASE(existing_data_reindex) {
     // We're going to share this fs::path between two wrappers
     fs::path ph = GetDataDir() / "existing_data_reindex";
     create_directories(ph);
 
     // Set up a non-obfuscated wrapper to write some initial data.
     std::unique_ptr<CDBWrapper> dbw =
         std::make_unique<CDBWrapper>(ph, (1 << 10), false, false, false);
     char key = 'k';
     uint256 in = InsecureRand256();
     uint256 res;
 
     BOOST_CHECK(dbw->Write(key, in));
     BOOST_CHECK(dbw->Read(key, res));
     BOOST_CHECK_EQUAL(res.ToString(), in.ToString());
 
     // Call the destructor to free leveldb LOCK
     dbw.reset();
 
     // Simulate a -reindex by wiping the existing data store
     CDBWrapper odbw(ph, (1 << 10), false, true, true);
 
     // Check that the key/val we wrote with unobfuscated wrapper doesn't exist
     uint256 res2;
     BOOST_CHECK(!odbw.Read(key, res2));
     BOOST_CHECK(!is_null_key(dbwrapper_private::GetObfuscateKey(odbw)));
 
     uint256 in2 = InsecureRand256();
     uint256 res3;
 
     // Check that we can write successfully
     BOOST_CHECK(odbw.Write(key, in2));
     BOOST_CHECK(odbw.Read(key, res3));
     BOOST_CHECK_EQUAL(res3.ToString(), in2.ToString());
 }
 
 BOOST_AUTO_TEST_CASE(iterator_ordering) {
     fs::path ph = GetDataDir() / "iterator_ordering";
     CDBWrapper dbw(ph, (1 << 20), true, false, false);
     for (int x = 0x00; x < 256; ++x) {
         uint8_t key = x;
         uint32_t value = x * x;
         if (!(x & 1)) {
             BOOST_CHECK(dbw.Write(key, value));
         }
     }
 
     // Check that creating an iterator creates a snapshot
     std::unique_ptr<CDBIterator> it(
         const_cast<CDBWrapper &>(dbw).NewIterator());
 
     for (unsigned int x = 0x00; x < 256; ++x) {
         uint8_t key = x;
         uint32_t value = x * x;
         if (x & 1) {
             BOOST_CHECK(dbw.Write(key, value));
         }
     }
 
     for (const int seek_start : {0x00, 0x80}) {
         it->Seek((uint8_t)seek_start);
         for (unsigned int x = seek_start; x < 255; ++x) {
             uint8_t key;
             uint32_t value;
             BOOST_CHECK(it->Valid());
             // Avoid spurious errors about invalid iterator's  key and value in
             // case of failure
             if (!it->Valid()) {
                 break;
             }
             BOOST_CHECK(it->GetKey(key));
             if (x & 1) {
                 BOOST_CHECK_EQUAL(key, x + 1);
                 continue;
             }
             BOOST_CHECK(it->GetValue(value));
             BOOST_CHECK_EQUAL(key, x);
             BOOST_CHECK_EQUAL(value, x * x);
             it->Next();
         }
         BOOST_CHECK(!it->Valid());
     }
 }
 
 struct StringContentsSerializer {
     // Used to make two serialized objects the same while letting them have
     // different lengths. This is a terrible idea.
     std::string str;
     StringContentsSerializer() {}
     explicit StringContentsSerializer(const std::string &inp) : str(inp) {}
 
     StringContentsSerializer &operator+=(const std::string &s) {
         str += s;
         return *this;
     }
     StringContentsSerializer &operator+=(const StringContentsSerializer &s) {
         return *this += s.str;
     }
 
     ADD_SERIALIZE_METHODS;
 
     template <typename Stream, typename Operation>
     inline void SerializationOp(Stream &s, Operation ser_action) {
         if (ser_action.ForRead()) {
             str.clear();
             char c = 0;
             while (true) {
                 try {
                     READWRITE(c);
                     str.push_back(c);
                 } catch (const std::ios_base::failure &) {
                     break;
                 }
             }
         } else {
             for (size_t i = 0; i < str.size(); i++) {
                 READWRITE(str[i]);
             }
         }
     }
 };
 
 BOOST_AUTO_TEST_CASE(iterator_string_ordering) {
     char buf[10];
 
     fs::path ph = GetDataDir() / "iterator_string_ordering";
     CDBWrapper dbw(ph, (1 << 20), true, false, false);
     for (int x = 0x00; x < 10; ++x) {
         for (int y = 0; y < 10; y++) {
             snprintf(buf, sizeof(buf), "%d", x);
             StringContentsSerializer key(buf);
             for (int z = 0; z < y; z++) {
                 key += key;
             }
             uint32_t value = x * x;
             BOOST_CHECK(dbw.Write(key, value));
         }
     }
 
     std::unique_ptr<CDBIterator> it(
         const_cast<CDBWrapper &>(dbw).NewIterator());
     for (const int seek_start : {0, 5}) {
         snprintf(buf, sizeof(buf), "%d", seek_start);
         StringContentsSerializer seek_key(buf);
         it->Seek(seek_key);
         for (unsigned int x = seek_start; x < 10; ++x) {
             for (int y = 0; y < 10; y++) {
                 snprintf(buf, sizeof(buf), "%d", x);
                 std::string exp_key(buf);
                 for (int z = 0; z < y; z++) {
                     exp_key += exp_key;
                 }
                 StringContentsSerializer key;
                 uint32_t value;
                 BOOST_CHECK(it->Valid());
                 // Avoid spurious errors about invalid iterator's key and value
                 // in case of failure
                 if (!it->Valid()) {
                     break;
                 }
                 BOOST_CHECK(it->GetKey(key));
                 BOOST_CHECK(it->GetValue(value));
                 BOOST_CHECK_EQUAL(key.str, exp_key);
                 BOOST_CHECK_EQUAL(value, x * x);
                 it->Next();
             }
         }
         BOOST_CHECK(!it->Valid());
     }
 }
 
 BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/util/system.h b/src/util/system.h
index 524d1883d..0bc9a9708 100644
--- a/src/util/system.h
+++ b/src/util/system.h
@@ -1,450 +1,451 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
 // Copyright (c) 2009-2019 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 /**
  * Server/client environment: argument handling, config file parsing,
  * thread wrappers, startup time
  */
 #ifndef BITCOIN_UTIL_SYSTEM_H
 #define BITCOIN_UTIL_SYSTEM_H
 
 #if defined(HAVE_CONFIG_H)
 #include <config/bitcoin-config.h>
 #endif
 
 #include <attributes.h>
 #include <compat.h>
 #include <compat/assumptions.h>
 #include <fs.h>
 #include <logging.h>
 #include <optional.h>
 #include <sync.h>
 #include <tinyformat.h>
 #include <util/settings.h>
 #include <util/threadnames.h>
 #include <util/time.h>
 
 #include <boost/thread/condition_variable.hpp> // for boost::thread_interrupted
 
 #include <cstdint>
 #include <exception>
 #include <map>
 #include <set>
 #include <string>
 #include <utility>
 #include <vector>
 
 // Application startup time (used for uptime calculation)
 int64_t GetStartupTime();
 
 extern const char *const BITCOIN_CONF_FILENAME;
 
 void SetupEnvironment();
 bool SetupNetworking();
 
 template <typename... Args> bool error(const char *fmt, const Args &... args) {
     LogPrintf("ERROR: %s\n", tfm::format(fmt, args...));
     return false;
 }
 
 void PrintExceptionContinue(const std::exception *pex, const char *pszThread);
 bool FileCommit(FILE *file);
 bool TruncateFile(FILE *file, unsigned int length);
 int RaiseFileDescriptorLimit(int nMinFD);
 void AllocateFileRange(FILE *file, unsigned int offset, unsigned int length);
 bool RenameOver(fs::path src, fs::path dest);
 bool LockDirectory(const fs::path &directory, const std::string lockfile_name,
                    bool probe_only = false);
 void UnlockDirectory(const fs::path &directory,
                      const std::string &lockfile_name);
 bool DirIsWritable(const fs::path &directory);
 bool CheckDiskSpace(const fs::path &dir, uint64_t additional_bytes = 0);
 
 /**
  * Release all directory locks. This is used for unit testing only, at runtime
  * the global destructor will take care of the locks.
  */
 void ReleaseDirectoryLocks();
 
 bool TryCreateDirectories(const fs::path &p);
 fs::path GetDefaultDataDir();
 // The blocks directory is always net specific.
 const fs::path &GetBlocksDir();
 const fs::path &GetDataDir(bool fNetSpecific = true);
 // Return true if -datadir option points to a valid directory or is not
 // specified.
 bool CheckDataDirOption();
 /** Tests only */
 void ClearDatadirCache();
 fs::path GetConfigFile(const std::string &confPath);
 #ifdef WIN32
 fs::path GetSpecialFolderPath(int nFolder, bool fCreate = true);
 #endif
 #if defined(HAVE_SYSTEM)
 void runCommand(const std::string &strCommand);
 #endif
 
 NODISCARD bool ParseKeyValue(std::string &key, std::string &val);
 
 /**
  * Most paths passed as configuration arguments are treated as relative to
  * the datadir if they are not absolute.
  *
  * @param path The path to be conditionally prefixed with datadir.
  * @param net_specific Forwarded to GetDataDir().
  * @return The normalized path.
  */
 fs::path AbsPathForConfigVal(const fs::path &path, bool net_specific = true);
 
 inline bool IsSwitchChar(char c) {
 #ifdef WIN32
     return c == '-' || c == '/';
 #else
     return c == '-';
 #endif
 }
 
 enum class OptionsCategory {
     OPTIONS,
     CONNECTION,
     WALLET,
     WALLET_DEBUG_TEST,
     ZMQ,
     DEBUG_TEST,
     CHAINPARAMS,
     NODE_RELAY,
     BLOCK_CREATION,
     RPC,
     GUI,
     COMMANDS,
     REGISTER_COMMANDS,
 
     // Always the last option to avoid printing these in the help
     HIDDEN,
 
     // Avalanche is still experimental, so we keep it hidden for now.
     AVALANCHE,
 };
 
 struct SectionInfo {
     std::string m_name;
     std::string m_file;
     int m_line;
 };
 
 class ArgsManager {
 public:
     enum Flags {
         // Boolean options can accept negation syntax -noOPTION or -noOPTION=1
         ALLOW_BOOL = 0x01,
         ALLOW_INT = 0x02,
         ALLOW_STRING = 0x04,
         ALLOW_ANY = ALLOW_BOOL | ALLOW_INT | ALLOW_STRING,
         DEBUG_ONLY = 0x100,
         /* Some options would cause cross-contamination if values for
          * mainnet were used while running on regtest/testnet (or vice-versa).
          * Setting them as NETWORK_ONLY ensures that sharing a config file
          * between mainnet and regtest/testnet won't cause problems due to these
          * parameters by accident. */
         NETWORK_ONLY = 0x200,
         // This argument's value is sensitive (such as a password).
         SENSITIVE = 0x400,
     };
 
 protected:
     struct Arg {
         std::string m_help_param;
         std::string m_help_text;
         unsigned int m_flags;
     };
 
     mutable RecursiveMutex cs_args;
     util::Settings m_settings GUARDED_BY(cs_args);
     std::string m_network GUARDED_BY(cs_args);
     std::set<std::string> m_network_only_args GUARDED_BY(cs_args);
     std::map<OptionsCategory, std::map<std::string, Arg>>
         m_available_args GUARDED_BY(cs_args);
     std::list<SectionInfo> m_config_sections GUARDED_BY(cs_args);
 
     NODISCARD bool ReadConfigStream(std::istream &stream,
                                     const std::string &filepath,
                                     std::string &error,
                                     bool ignore_invalid_keys = false);
 
     /**
      * Returns true if settings values from the default section should be used,
      * depending on the current network and whether the setting is
      * network-specific.
      */
     bool UseDefaultSection(const std::string &arg) const
         EXCLUSIVE_LOCKS_REQUIRED(cs_args);
 
     /**
      * Get setting value.
      *
      * Result will be null if setting was unset, true if "-setting" argument was
      * passed false if "-nosetting" argument was passed, and a string if a
      * "-setting=value" argument was passed.
      */
     util::SettingsValue GetSetting(const std::string &arg) const;
 
     /**
      * Get list of setting values.
      */
     std::vector<util::SettingsValue>
     GetSettingsList(const std::string &arg) const;
 
 public:
     ArgsManager();
 
     /**
      * Select the network in use
      */
     void SelectConfigNetwork(const std::string &network);
 
     NODISCARD bool ParseParameters(int argc, const char *const argv[],
                                    std::string &error);
-    bool ReadConfigFiles(std::string &error, bool ignore_invalid_keys = false);
+    NODISCARD bool ReadConfigFiles(std::string &error,
+                                   bool ignore_invalid_keys = false);
 
     /**
      * Log warnings for options in m_section_only_args when they are specified
      * in the default section but not overridden on the command line or in a
      * network-specific section in the config file.
      */
     const std::set<std::string> GetUnsuitableSectionOnlyArgs() const;
 
     /**
      * Log warnings for unrecognized section names in the config file.
      */
     const std::list<SectionInfo> GetUnrecognizedSections() const;
 
     /**
      * Return a vector of strings of the given argument
      *
      * @param strArg Argument to get (e.g. "-foo")
      * @return command-line arguments
      */
     std::vector<std::string> GetArgs(const std::string &strArg) const;
 
     /**
      * Return true if the given argument has been manually set.
      *
      * @param strArg Argument to get (e.g. "-foo")
      * @return true if the argument has been set
      */
     bool IsArgSet(const std::string &strArg) const;
 
     /**
      * Return true if the argument was originally passed as a negated option,
      * i.e. -nofoo.
      *
      * @param strArg Argument to get (e.g. "-foo")
      * @return true if the argument was passed negated
      */
     bool IsArgNegated(const std::string &strArg) const;
 
     /**
      * Return string argument or default value.
      *
      * @param strArg Argument to get (e.g. "-foo")
      * @param default (e.g. "1")
      * @return command-line argument or default value
      */
     std::string GetArg(const std::string &strArg,
                        const std::string &strDefault) const;
 
     /**
      * Return integer argument or default value.
      *
      * @param strArg Argument to get (e.g. "-foo")
      * @param default (e.g. 1)
      * @return command-line argument (0 if invalid number) or default value
      */
     int64_t GetArg(const std::string &strArg, int64_t nDefault) const;
 
     /**
      * Return boolean argument or default value.
      *
      * @param strArg Argument to get (e.g. "-foo")
      * @param default (true or false)
      * @return command-line argument or default value
      */
     bool GetBoolArg(const std::string &strArg, bool fDefault) const;
 
     /**
      * Set an argument if it doesn't already have a value.
      *
      * @param strArg Argument to set (e.g. "-foo")
      * @param strValue Value (e.g. "1")
      * @return true if argument gets set, false if it already had a value
      */
     bool SoftSetArg(const std::string &strArg, const std::string &strValue);
 
     /**
      * Set a boolean argument if it doesn't already have a value.
      *
      * @param strArg Argument to set (e.g. "-foo")
      * @param fValue Value (e.g. false)
      * @return true if argument gets set, false if it already had a value
      */
     bool SoftSetBoolArg(const std::string &strArg, bool fValue);
 
     // Forces an arg setting. Called by SoftSetArg() if the arg hasn't already
     // been set. Also called directly in testing.
     void ForceSetArg(const std::string &strArg, const std::string &strValue);
 
     // Forces a multi arg setting, used only in testing
     void ForceSetMultiArg(const std::string &strArg,
                           const std::vector<std::string> &values);
 
     /**
      * Looks for -regtest, -testnet and returns the appropriate BIP70 chain
      * name.
      * @return CBaseChainParams::MAIN by default; raises runtime error if an
      * invalid combination is given.
      */
     std::string GetChainName() const;
 
     /**
      * Add argument
      */
     void AddArg(const std::string &name, const std::string &help,
                 unsigned int flags, const OptionsCategory &cat);
 
     /**
      * Remove a forced arg setting, used only in testing.
      */
     void ClearForcedArg(const std::string &strArg);
 
     /**
      * Add many hidden arguments
      */
     void AddHiddenArgs(const std::vector<std::string> &args);
 
     /**
      * Clear available arguments
      */
     void ClearArgs() {
         LOCK(cs_args);
         m_available_args.clear();
         m_network_only_args.clear();
     }
 
     /**
      * Get the help string
      */
     std::string GetHelpMessage() const;
 
     /**
      * Return Flags for known arg.
      * Return nullopt for unknown arg.
      */
     Optional<unsigned int> GetArgFlags(const std::string &name) const;
 
     /**
      * Log the config file options and the command line arguments,
      * useful for troubleshooting.
      */
     void LogArgs() const;
 
 private:
     // Helper function for LogArgs().
     void
     logArgsPrefix(const std::string &prefix, const std::string &section,
                   const std::map<std::string, std::vector<util::SettingsValue>>
                       &args) const;
 };
 
 extern ArgsManager gArgs;
 
 /**
  * @return true if help has been requested via a command-line arg
  */
 bool HelpRequested(const ArgsManager &args);
 
 /**
  * Format a string to be used as group of options in help messages.
  *
  * @param message Group name (e.g. "RPC server options:")
  * @return the formatted string
  */
 std::string HelpMessageGroup(const std::string &message);
 
 /**
  * Format a string to be used as option description in help messages.
  *
  * @param option Option message (e.g. "-rpcuser=<user>")
  * @param message Option description (e.g. "Username for JSON-RPC connections")
  * @return the formatted string
  */
 std::string HelpMessageOpt(const std::string &option,
                            const std::string &message);
 
 /**
  * Return the number of cores available on the current system.
  * @note This does count virtual cores, such as those provided by
  * HyperThreading.
  */
 int GetNumCores();
 
 /**
  * .. and a wrapper that just calls func once
  */
 template <typename Callable> void TraceThread(const char *name, Callable func) {
     util::ThreadRename(name);
     try {
         LogPrintf("%s thread start\n", name);
         func();
         LogPrintf("%s thread exit\n", name);
     } catch (const boost::thread_interrupted &) {
         LogPrintf("%s thread interrupt\n", name);
         throw;
     } catch (const std::exception &e) {
         PrintExceptionContinue(&e, name);
         throw;
     } catch (...) {
         PrintExceptionContinue(nullptr, name);
         throw;
     }
 }
 
 std::string CopyrightHolders(const std::string &strPrefix);
 
 /**
  * On platforms that support it, tell the kernel the calling thread is
  * CPU-intensive and non-interactive. See SCHED_BATCH in sched(7) for details.
  *
  */
 void ScheduleBatchPriority();
 
 namespace util {
 
 //! Simplification of std insertion
 template <typename Tdst, typename Tsrc>
 inline void insert(Tdst &dst, const Tsrc &src) {
     dst.insert(dst.begin(), src.begin(), src.end());
 }
 template <typename TsetT, typename Tsrc>
 inline void insert(std::set<TsetT> &dst, const Tsrc &src) {
     dst.insert(src.begin(), src.end());
 }
 
 #ifdef WIN32
 class WinCmdLineArgs {
 public:
     WinCmdLineArgs();
     ~WinCmdLineArgs();
     std::pair<int, char **> get();
 
 private:
     int argc;
     char **argv;
     std::vector<std::string> args;
 };
 #endif
 
 } // namespace util
 
 #endif // BITCOIN_UTIL_SYSTEM_H