diff --git a/src/util.cpp b/src/util.cpp
index d0777a658d..fac034954a 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -1,741 +1,746 @@
 // 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.
 
 #if defined(HAVE_CONFIG_H)
 #include "config/bitcoin-config.h"
 #endif
 
 #include "util.h"
 
 #include "chainparamsbase.h"
 #include "fs.h"
 #include "random.h"
 #include "serialize.h"
 #include "utilstrencodings.h"
 #include "utiltime.h"
 
 #include <cstdarg>
 
 #if (defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__))
 #include <pthread.h>
 #include <pthread_np.h>
 #endif
 
 #ifndef WIN32
 // for posix_fallocate
 #ifdef __linux__
 
 #ifdef _POSIX_C_SOURCE
 #undef _POSIX_C_SOURCE
 #endif
 
 #define _POSIX_C_SOURCE 200112L
 
 #endif // __linux__
 
 #include <algorithm>
 #include <fcntl.h>
 #include <sys/resource.h>
 #include <sys/stat.h>
 
 #else
 
 #ifdef _MSC_VER
 #pragma warning(disable : 4786)
 #pragma warning(disable : 4804)
 #pragma warning(disable : 4805)
 #pragma warning(disable : 4717)
 #endif
 
 #ifdef _WIN32_WINNT
 #undef _WIN32_WINNT
 #endif
 #define _WIN32_WINNT 0x0501
 
 #ifdef _WIN32_IE
 #undef _WIN32_IE
 #endif
 #define _WIN32_IE 0x0501
 
 #define WIN32_LEAN_AND_MEAN 1
 #ifndef NOMINMAX
 #define NOMINMAX
 #endif
 
 #include <io.h> /* for _commit */
 #include <shlobj.h>
 #endif
 
 #ifdef HAVE_SYS_PRCTL_H
 #include <sys/prctl.h>
 #endif
 
 #ifdef HAVE_MALLOPT_ARENA_MAX
 #include <malloc.h>
 #endif
 
 #include <boost/program_options/detail/config_file.hpp>
 #include <boost/thread.hpp>
 
 #include <openssl/conf.h>
 #include <openssl/rand.h>
 
 // Application startup time (used for uptime calculation)
 const int64_t nStartupTime = GetTime();
 
 const char *const BITCOIN_CONF_FILENAME = "bitcoin.conf";
 const char *const BITCOIN_PID_FILENAME = "bitcoind.pid";
 
 ArgsManager gArgs;
 
 CTranslationInterface translationInterface;
 
 /** Init OpenSSL library multithreading support */
 static CCriticalSection **ppmutexOpenSSL;
 void locking_callback(int mode, int i, const char *file,
                       int line) NO_THREAD_SAFETY_ANALYSIS {
     if (mode & CRYPTO_LOCK) {
         ENTER_CRITICAL_SECTION(*ppmutexOpenSSL[i]);
     } else {
         LEAVE_CRITICAL_SECTION(*ppmutexOpenSSL[i]);
     }
 }
 
 // Init
 class CInit {
 public:
     CInit() {
         // Init OpenSSL library multithreading support.
         ppmutexOpenSSL = (CCriticalSection **)OPENSSL_malloc(
             CRYPTO_num_locks() * sizeof(CCriticalSection *));
         for (int i = 0; i < CRYPTO_num_locks(); i++) {
             ppmutexOpenSSL[i] = new CCriticalSection();
         }
         CRYPTO_set_locking_callback(locking_callback);
 
         // OpenSSL can optionally load a config file which lists optional
         // loadable modules and engines. We don't use them so we don't require
         // the config. However some of our libs may call functions which attempt
         // to load the config file, possibly resulting in an exit() or crash if
         // it is missing or corrupt. Explicitly tell OpenSSL not to try to load
         // the file. The result for our libs will be that the config appears to
         // have been loaded and there are no modules/engines available.
         OPENSSL_no_config();
 
 #ifdef WIN32
         // Seed OpenSSL PRNG with current contents of the screen.
         RAND_screen();
 #endif
 
         // Seed OpenSSL PRNG with performance counter.
         RandAddSeed();
     }
     ~CInit() {
         // Securely erase the memory used by the PRNG.
         RAND_cleanup();
         // Shutdown OpenSSL library multithreading support.
         CRYPTO_set_locking_callback(nullptr);
         for (int i = 0; i < CRYPTO_num_locks(); i++) {
             delete ppmutexOpenSSL[i];
         }
         OPENSSL_free(ppmutexOpenSSL);
     }
 } instance_of_cinit;
 
 /**
  * Interpret a string argument as a boolean.
  *
  * The definition of atoi() requires that non-numeric string values like "foo",
  * return 0. This means that if a user unintentionally supplies a non-integer
  * argument here, the return value is always false. This means that -foo=false
  * does what the user probably expects, but -foo=true is well defined but does
  * not do what they probably expected.
  *
  * The return value of atoi() is undefined when given input not representable as
  * an int. On most systems this means string value between "-2147483648" and
  * "2147483647" are well defined (this method will return true). Setting
  * -txindex=2147483648 on most systems, however, is probably undefined.
  *
  * For a more extensive discussion of this topic (and a wide range of opinions
  * on the Right Way to change this code), see PR12713.
  */
 static bool InterpretBool(const std::string &strValue) {
     if (strValue.empty()) {
         return true;
     }
     return (atoi(strValue) != 0);
 }
 
 /**
  * Interpret -nofoo as if the user supplied -foo=0.
  *
  * This method also tracks when the -no form was supplied, and treats "-foo" as
  * a negated option when this happens. This can be later checked using the
  * IsArgNegated() method. One use case for this is to have a way to disable
  * options that are not normally boolean (e.g. using -nodebuglogfile to request
  * that debug log output is not sent to any file at all).
  */
 void ArgsManager::InterpretNegatedOption(std::string &key, std::string &val) {
     if (key.substr(0, 3) == "-no") {
         bool bool_val = InterpretBool(val);
         if (!bool_val) {
             // Double negatives like -nofoo=0 are supported (but discouraged)
             LogPrintf(
                 "Warning: parsed potentially confusing double-negative %s=%s\n",
                 key, val);
         }
         key.erase(1, 2);
         m_negated_args.insert(key);
         val = bool_val ? "0" : "1";
     } else {
         // In an invocation like "bitcoind -nofoo -foo" we want to unmark -foo
         // as negated when we see the second option.
         m_negated_args.erase(key);
     }
 }
 
 void ArgsManager::ParseParameters(int argc, const char *const argv[]) {
     LOCK(cs_args);
     mapArgs.clear();
     mapMultiArgs.clear();
     m_negated_args.clear();
 
     for (int i = 1; i < argc; i++) {
         std::string key(argv[i]);
         std::string val;
         size_t is_index = key.find('=');
         if (is_index != std::string::npos) {
             val = key.substr(is_index + 1);
             key.erase(is_index);
         }
 #ifdef WIN32
         std::transform(key.begin(), key.end(), key.begin(), ::tolower);
         if (key[0] == '/') {
             key[0] = '-';
         }
 #endif
 
         if (key[0] != '-') {
             break;
         }
 
         // Transform --foo to -foo
         if (key.length() > 1 && key[1] == '-') {
             key.erase(0, 1);
         }
 
         // Transform -nofoo to -foo=0
         InterpretNegatedOption(key, val);
 
         mapArgs[key] = val;
         mapMultiArgs[key].push_back(val);
     }
 }
 
 std::vector<std::string> ArgsManager::GetArgs(const std::string &strArg) const {
     LOCK(cs_args);
     auto it = mapMultiArgs.find(strArg);
     if (it != mapMultiArgs.end()) {
         return it->second;
     }
     return {};
 }
 
 bool ArgsManager::IsArgSet(const std::string &strArg) const {
     LOCK(cs_args);
     return mapArgs.count(strArg);
 }
 
 bool ArgsManager::IsArgNegated(const std::string &strArg) const {
     LOCK(cs_args);
     return m_negated_args.find(strArg) != m_negated_args.end();
 }
 
 std::string ArgsManager::GetArg(const std::string &strArg,
                                 const std::string &strDefault) const {
     LOCK(cs_args);
     auto it = mapArgs.find(strArg);
     if (it != mapArgs.end()) {
         return it->second;
     }
     return strDefault;
 }
 
 int64_t ArgsManager::GetArg(const std::string &strArg, int64_t nDefault) const {
     LOCK(cs_args);
     auto it = mapArgs.find(strArg);
     if (it != mapArgs.end()) {
         return atoi64(it->second);
     }
     return nDefault;
 }
 
 bool ArgsManager::GetBoolArg(const std::string &strArg, bool fDefault) const {
     LOCK(cs_args);
     auto it = mapArgs.find(strArg);
     if (it != mapArgs.end()) {
         return InterpretBool(it->second);
     }
     return fDefault;
 }
 
 bool ArgsManager::SoftSetArg(const std::string &strArg,
                              const std::string &strValue) {
     LOCK(cs_args);
     if (IsArgSet(strArg)) {
         return false;
     }
     ForceSetArg(strArg, strValue);
     return true;
 }
 
 bool ArgsManager::SoftSetBoolArg(const std::string &strArg, bool fValue) {
     if (fValue) {
         return SoftSetArg(strArg, std::string("1"));
     } else {
         return SoftSetArg(strArg, std::string("0"));
     }
 }
 
 void ArgsManager::ForceSetArg(const std::string &strArg,
                               const std::string &strValue) {
     LOCK(cs_args);
     mapArgs[strArg] = strValue;
     mapMultiArgs[strArg] = {strValue};
 }
 
 /**
  * This function is only used for testing purpose so
  * so we should not worry about element uniqueness and
  * integrity of mapMultiArgs data structure
  */
 void ArgsManager::ForceSetMultiArg(const std::string &strArg,
                                    const std::string &strValue) {
     LOCK(cs_args);
     if (mapArgs.count(strArg) == 0) {
         mapArgs[strArg] = strValue;
     }
     mapMultiArgs[strArg].push_back(strValue);
 }
 
 void ArgsManager::ClearArg(const std::string &strArg) {
     LOCK(cs_args);
     mapArgs.erase(strArg);
 }
 
 bool HelpRequested(const ArgsManager &args) {
     return args.IsArgSet("-?") || args.IsArgSet("-h") || args.IsArgSet("-help");
 }
 
 static const int screenWidth = 79;
 static const int optIndent = 2;
 static const int msgIndent = 7;
 
 std::string HelpMessageGroup(const std::string &message) {
     return std::string(message) + std::string("\n\n");
 }
 
 std::string HelpMessageOpt(const std::string &option,
                            const std::string &message) {
     return std::string(optIndent, ' ') + std::string(option) +
            std::string("\n") + std::string(msgIndent, ' ') +
            FormatParagraph(message, screenWidth - msgIndent, msgIndent) +
            std::string("\n\n");
 }
 
 static std::string FormatException(const std::exception *pex,
                                    const char *pszThread) {
 #ifdef WIN32
     char pszModule[MAX_PATH] = "";
     GetModuleFileNameA(nullptr, pszModule, sizeof(pszModule));
 #else
     const char *pszModule = "bitcoin";
 #endif
     if (pex) {
         return strprintf("EXCEPTION: %s       \n%s       \n%s in %s       \n",
                          typeid(*pex).name(), pex->what(), pszModule,
                          pszThread);
     } else {
         return strprintf("UNKNOWN EXCEPTION       \n%s in %s       \n",
                          pszModule, pszThread);
     }
 }
 
 void PrintExceptionContinue(const std::exception *pex, const char *pszThread) {
     std::string message = FormatException(pex, pszThread);
     LogPrintf("\n\n************************\n%s\n", message);
     fprintf(stderr, "\n\n************************\n%s\n", message.c_str());
 }
 
 fs::path GetDefaultDataDir() {
 // Windows < Vista: C:\Documents and Settings\Username\Application Data\Bitcoin
 // Windows >= Vista: C:\Users\Username\AppData\Roaming\Bitcoin
 // Mac: ~/Library/Application Support/Bitcoin
 // Unix: ~/.bitcoin
 #ifdef WIN32
     // Windows
     return GetSpecialFolderPath(CSIDL_APPDATA) / "Bitcoin";
 #else
     fs::path pathRet;
     char *pszHome = getenv("HOME");
     if (pszHome == nullptr || strlen(pszHome) == 0) {
         pathRet = fs::path("/");
     } else {
         pathRet = fs::path(pszHome);
     }
 #ifdef MAC_OSX
     // Mac
     return pathRet / "Library/Application Support/Bitcoin";
 #else
     // Unix
     return pathRet / ".bitcoin";
 #endif
 #endif
 }
 
 static fs::path pathCached;
 static fs::path pathCachedNetSpecific;
 static CCriticalSection csPathCached;
 
 const fs::path &GetDataDir(bool fNetSpecific) {
     LOCK(csPathCached);
 
     fs::path &path = fNetSpecific ? pathCachedNetSpecific : pathCached;
 
     // This can be called during exceptions by LogPrintf(), so we cache the
     // value so we don't have to do memory allocations after that.
     if (!path.empty()) {
         return path;
     }
 
     if (gArgs.IsArgSet("-datadir")) {
         path = fs::system_complete(gArgs.GetArg("-datadir", ""));
         if (!fs::is_directory(path)) {
             path = "";
             return path;
         }
     } else {
         path = GetDefaultDataDir();
     }
 
     if (fNetSpecific) {
         path /= BaseParams().DataDir();
     }
 
     fs::create_directories(path);
 
     return path;
 }
 
 void ClearDatadirCache() {
     LOCK(csPathCached);
 
     pathCached = fs::path();
     pathCachedNetSpecific = fs::path();
 }
 
 fs::path GetConfigFile(const std::string &confPath) {
     fs::path pathConfigFile(confPath);
     if (!pathConfigFile.is_complete()) {
         pathConfigFile = GetDataDir(false) / pathConfigFile;
     }
 
     return pathConfigFile;
 }
 
 void ArgsManager::ReadConfigStream(std::istream &stream) {
     LOCK(cs_args);
 
     std::set<std::string> setOptions;
     setOptions.insert("*");
 
     for (boost::program_options::detail::config_file_iterator
              it(stream, setOptions),
          end;
          it != end; ++it) {
         // Don't overwrite existing settings so command line settings override
         // bitcoin.conf
         std::string strKey = std::string("-") + it->string_key;
         std::string strValue = it->value[0];
         InterpretNegatedOption(strKey, strValue);
         if (mapArgs.count(strKey) == 0) {
             mapArgs[strKey] = strValue;
         }
         mapMultiArgs[strKey].push_back(strValue);
     }
 }
 
 void ArgsManager::ReadConfigFile(const std::string &confPath) {
     fs::ifstream stream(GetConfigFile(confPath));
 
     // ok to not have a config file
     if (stream.good()) {
         ReadConfigStream(stream);
     }
 
     // If datadir is changed in .conf file:
     ClearDatadirCache();
+    if (!fs::is_directory(GetDataDir(false))) {
+        throw std::runtime_error(
+            strprintf("specified data directory \"%s\" does not exist.",
+                      gArgs.GetArg("-datadir", "").c_str()));
+    }
 }
 
 std::string ArgsManager::GetChainName() const {
     bool fRegTest = GetBoolArg("-regtest", false);
     bool fTestNet = GetBoolArg("-testnet", false);
 
     if (fTestNet && fRegTest) {
         throw std::runtime_error(
             "Invalid combination of -regtest and -testnet.");
     }
     if (fRegTest) {
         return CBaseChainParams::REGTEST;
     }
     if (fTestNet) {
         return CBaseChainParams::TESTNET;
     }
     return CBaseChainParams::MAIN;
 }
 
 #ifndef WIN32
 fs::path GetPidFile() {
     fs::path pathPidFile(gArgs.GetArg("-pid", BITCOIN_PID_FILENAME));
     if (!pathPidFile.is_complete()) {
         pathPidFile = GetDataDir() / pathPidFile;
     }
     return pathPidFile;
 }
 
 void CreatePidFile(const fs::path &path, pid_t pid) {
     FILE *file = fsbridge::fopen(path, "w");
     if (file) {
         fprintf(file, "%d\n", pid);
         fclose(file);
     }
 }
 #endif
 
 bool RenameOver(fs::path src, fs::path dest) {
 #ifdef WIN32
     return MoveFileExA(src.string().c_str(), dest.string().c_str(),
                        MOVEFILE_REPLACE_EXISTING) != 0;
 #else
     int rc = std::rename(src.string().c_str(), dest.string().c_str());
     return (rc == 0);
 #endif /* WIN32 */
 }
 
 /**
  * Ignores exceptions thrown by Boost's create_directories if the requested
  * directory exists. Specifically handles case where path p exists, but it
  * wasn't possible for the user to write to the parent directory.
  */
 bool TryCreateDirectories(const fs::path &p) {
     try {
         return fs::create_directories(p);
     } catch (const fs::filesystem_error &) {
         if (!fs::exists(p) || !fs::is_directory(p)) {
             throw;
         }
     }
 
     // create_directory didn't create the directory, it had to have existed
     // already.
     return false;
 }
 
 void FileCommit(FILE *file) {
     // Harmless if redundantly called.
     fflush(file);
 #ifdef WIN32
     HANDLE hFile = (HANDLE)_get_osfhandle(_fileno(file));
     FlushFileBuffers(hFile);
 #else
 #if defined(__linux__) || defined(__NetBSD__)
     fdatasync(fileno(file));
 #elif defined(__APPLE__) && defined(F_FULLFSYNC)
     fcntl(fileno(file), F_FULLFSYNC, 0);
 #else
     fsync(fileno(file));
 #endif
 #endif
 }
 
 bool TruncateFile(FILE *file, unsigned int length) {
 #if defined(WIN32)
     return _chsize(_fileno(file), length) == 0;
 #else
     return ftruncate(fileno(file), length) == 0;
 #endif
 }
 
 /**
  * This function tries to raise the file descriptor limit to the requested
  * number. It returns the actual file descriptor limit (which may be more or
  * less than nMinFD)
  */
 int RaiseFileDescriptorLimit(int nMinFD) {
 #if defined(WIN32)
     return 2048;
 #else
     struct rlimit limitFD;
     if (getrlimit(RLIMIT_NOFILE, &limitFD) != -1) {
         if (limitFD.rlim_cur < (rlim_t)nMinFD) {
             limitFD.rlim_cur = nMinFD;
             if (limitFD.rlim_cur > limitFD.rlim_max) {
                 limitFD.rlim_cur = limitFD.rlim_max;
             }
             setrlimit(RLIMIT_NOFILE, &limitFD);
             getrlimit(RLIMIT_NOFILE, &limitFD);
         }
         return limitFD.rlim_cur;
     }
     // getrlimit failed, assume it's fine.
     return nMinFD;
 #endif
 }
 
 /**
  * This function tries to make a particular range of a file allocated
  * (corresponding to disk space) it is advisory, and the range specified in the
  * arguments will never contain live data.
  */
 void AllocateFileRange(FILE *file, unsigned int offset, unsigned int length) {
 #if defined(WIN32)
     // Windows-specific version.
     HANDLE hFile = (HANDLE)_get_osfhandle(_fileno(file));
     LARGE_INTEGER nFileSize;
     int64_t nEndPos = (int64_t)offset + length;
     nFileSize.u.LowPart = nEndPos & 0xFFFFFFFF;
     nFileSize.u.HighPart = nEndPos >> 32;
     SetFilePointerEx(hFile, nFileSize, 0, FILE_BEGIN);
     SetEndOfFile(hFile);
 #elif defined(MAC_OSX)
     // OSX specific version.
     fstore_t fst;
     fst.fst_flags = F_ALLOCATECONTIG;
     fst.fst_posmode = F_PEOFPOSMODE;
     fst.fst_offset = 0;
     fst.fst_length = (off_t)offset + length;
     fst.fst_bytesalloc = 0;
     if (fcntl(fileno(file), F_PREALLOCATE, &fst) == -1) {
         fst.fst_flags = F_ALLOCATEALL;
         fcntl(fileno(file), F_PREALLOCATE, &fst);
     }
     ftruncate(fileno(file), fst.fst_length);
 #elif defined(__linux__)
     // Version using posix_fallocate.
     off_t nEndPos = (off_t)offset + length;
     posix_fallocate(fileno(file), 0, nEndPos);
 #else
     // Fallback version
     // TODO: just write one byte per block
     static const char buf[65536] = {};
     fseek(file, offset, SEEK_SET);
     while (length > 0) {
         unsigned int now = 65536;
         if (length < now) {
             now = length;
         }
         // Allowed to fail; this function is advisory anyway.
         fwrite(buf, 1, now, file);
         length -= now;
     }
 #endif
 }
 
 #ifdef WIN32
 fs::path GetSpecialFolderPath(int nFolder, bool fCreate) {
     char pszPath[MAX_PATH] = "";
 
     if (SHGetSpecialFolderPathA(nullptr, pszPath, nFolder, fCreate)) {
         return fs::path(pszPath);
     }
 
     LogPrintf(
         "SHGetSpecialFolderPathA() failed, could not obtain requested path.\n");
     return fs::path("");
 }
 #endif
 
 void runCommand(const std::string &strCommand) {
     if (strCommand.empty()) {
         return;
     }
     int nErr = ::system(strCommand.c_str());
     if (nErr) {
         LogPrintf("runCommand error: system(%s) returned %d\n", strCommand,
                   nErr);
     }
 }
 
 void RenameThread(const char *name) {
 #if defined(PR_SET_NAME)
     // Only the first 15 characters are used (16 - NUL terminator)
     ::prctl(PR_SET_NAME, name, 0, 0, 0);
 #elif (defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__))
     pthread_set_name_np(pthread_self(), name);
 
 #elif defined(MAC_OSX)
     pthread_setname_np(name);
 #else
     // Prevent warnings for unused parameters...
     (void)name;
 #endif
 }
 
 void SetupEnvironment() {
 #ifdef HAVE_MALLOPT_ARENA_MAX
     // glibc-specific: On 32-bit systems set the number of arenas to 1. By
     // default, since glibc 2.10, the C library will create up to two heap
     // arenas per core. This is known to cause excessive virtual address space
     // usage in our usage. Work around it by setting the maximum number of
     // arenas to 1.
     if (sizeof(void *) == 4) {
         mallopt(M_ARENA_MAX, 1);
     }
 #endif
 // On most POSIX systems (e.g. Linux, but not BSD) the environment's locale may
 // be invalid, in which case the "C" locale is used as fallback.
 #if !defined(WIN32) && !defined(MAC_OSX) && !defined(__FreeBSD__) &&           \
     !defined(__OpenBSD__)
     try {
         // Raises a runtime error if current locale is invalid.
         std::locale("");
     } catch (const std::runtime_error &) {
         setenv("LC_ALL", "C", 1);
     }
 #endif
     // The path locale is lazy initialized and to avoid deinitialization errors
     // in multithreading environments, it is set explicitly by the main thread.
     // A dummy locale is used to extract the internal default locale, used by
     // fs::path, which is then used to explicitly imbue the path.
     std::locale loc = fs::path::imbue(std::locale::classic());
     fs::path::imbue(loc);
 }
 
 bool SetupNetworking() {
 #ifdef WIN32
     // Initialize Windows Sockets.
     WSADATA wsadata;
     int ret = WSAStartup(MAKEWORD(2, 2), &wsadata);
     if (ret != NO_ERROR || LOBYTE(wsadata.wVersion) != 2 ||
         HIBYTE(wsadata.wVersion) != 2) {
         return false;
     }
 #endif
     return true;
 }
 
 int GetNumCores() {
     return boost::thread::physical_concurrency();
 }
 
 std::string CopyrightHolders(const std::string &strPrefix) {
     return strPrefix +
            strprintf(_(COPYRIGHT_HOLDERS), _(COPYRIGHT_HOLDERS_SUBSTITUTION));
 }
 
 // Obtain the application startup time (used for uptime calculation)
 int64_t GetStartupTime() {
     return nStartupTime;
 }