26 files changed, 251 insertions, 154 deletions
diff --git a/src/Makefile.am b/src/Makefile.am
index 7c2fe56d9d..72e5cdb95d 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -4,8 +4,8 @@
 
 DIST_SUBDIRS = secp256k1 univalue
 
-AM_LDFLAGS = $(PTHREAD_CFLAGS) $(LIBTOOL_LDFLAGS) $(HARDENED_LDFLAGS) $(GPROF_LDFLAGS)
-AM_CXXFLAGS = $(HARDENED_CXXFLAGS) $(ERROR_CXXFLAGS) $(GPROF_CXXFLAGS)
+AM_LDFLAGS = $(PTHREAD_CFLAGS) $(LIBTOOL_LDFLAGS) $(HARDENED_LDFLAGS) $(GPROF_LDFLAGS) $(SANITIZER_LDFLAGS)
+AM_CXXFLAGS = $(HARDENED_CXXFLAGS) $(ERROR_CXXFLAGS) $(GPROF_CXXFLAGS) $(SANITIZER_CXXFLAGS)
 AM_CPPFLAGS = $(HARDENED_CPPFLAGS)
 EXTRA_LIBRARIES =
 
@@ -162,6 +162,7 @@ BITCOIN_CORE_H = \
   validation.h \
   validationinterface.h \
   versionbits.h \
+  walletinitinterface.h \
   wallet/coincontrol.h \
   wallet/crypter.h \
   wallet/db.h \
diff --git a/src/addrdb.cpp b/src/addrdb.cpp
index 675f3c28af..e4620e63c6 100644
--- a/src/addrdb.cpp
+++ b/src/addrdb.cpp
@@ -22,8 +22,8 @@ bool SerializeDB(Stream& stream, const Data& data)
     // Write and commit header, data
     try {
         CHashWriter hasher(SER_DISK, CLIENT_VERSION);
-        stream << FLATDATA(Params().MessageStart()) << data;
-        hasher << FLATDATA(Params().MessageStart()) << data;
+        stream << Params().MessageStart() << data;
+        hasher << Params().MessageStart() << data;
         stream << hasher.GetHash();
     } catch (const std::exception& e) {
         return error("%s: Serialize or I/O error - %s", __func__, e.what());
@@ -66,7 +66,7 @@ bool DeserializeDB(Stream& stream, Data& data, bool fCheckSum = true)
         CHashVerifier<Stream> verifier(&stream);
         // de-serialize file header (network specific magic number) and ..
         unsigned char pchMsgTmp[4];
-        verifier >> FLATDATA(pchMsgTmp);
+        verifier >> pchMsgTmp;
         // ... verify the network matches ours
         if (memcmp(pchMsgTmp, Params().MessageStart(), sizeof(pchMsgTmp)))
             return error("%s: Invalid network magic number", __func__);
diff --git a/src/bitcoind.cpp b/src/bitcoind.cpp
index db5e610684..df7fad89c2 100644
--- a/src/bitcoind.cpp
+++ b/src/bitcoind.cpp
@@ -18,6 +18,10 @@
 #include <httpserver.h>
 #include <httprpc.h>
 #include <utilstrencodings.h>
+#if ENABLE_WALLET
+#include <wallet/init.h>
+#endif
+#include <walletinitinterface.h>
 
 #include <boost/thread.hpp>
 
@@ -59,6 +63,12 @@ bool AppInit(int argc, char* argv[])
 {
     bool fRet = false;
 
+#if ENABLE_WALLET
+    g_wallet_init_interface.reset(new WalletInit);
+#else
+    g_wallet_init_interface.reset(new DummyWalletInit);
+#endif
+
     //
     // Parameters
     //
diff --git a/src/compressor.cpp b/src/compressor.cpp
index 86de2900e9..da639a01af 100644
--- a/src/compressor.cpp
+++ b/src/compressor.cpp
@@ -9,7 +9,15 @@
 #include <pubkey.h>
 #include <script/standard.h>
 
-bool CScriptCompressor::IsToKeyID(CKeyID &hash) const
+/*
+ * These check for scripts for which a special case with a shorter encoding is defined.
+ * They are implemented separately from the CScript test, as these test for exact byte
+ * sequence correspondences, and are more strict. For example, IsToPubKey also verifies
+ * whether the public key is valid (as invalid ones cannot be represented in compressed
+ * form).
+ */
+
+static bool IsToKeyID(const CScript& script, CKeyID &hash)
 {
     if (script.size() == 25 && script[0] == OP_DUP && script[1] == OP_HASH160
                             && script[2] == 20 && script[23] == OP_EQUALVERIFY
@@ -20,7 +28,7 @@ bool CScriptCompressor::IsToKeyID(CKeyID &hash) const
     return false;
 }
 
-bool CScriptCompressor::IsToScriptID(CScriptID &hash) const
+static bool IsToScriptID(const CScript& script, CScriptID &hash)
 {
     if (script.size() == 23 && script[0] == OP_HASH160 && script[1] == 20
                             && script[22] == OP_EQUAL) {
@@ -30,7 +38,7 @@ bool CScriptCompressor::IsToScriptID(CScriptID &hash) const
     return false;
 }
 
-bool CScriptCompressor::IsToPubKey(CPubKey &pubkey) const
+static bool IsToPubKey(const CScript& script, CPubKey &pubkey)
 {
     if (script.size() == 35 && script[0] == 33 && script[34] == OP_CHECKSIG
                             && (script[1] == 0x02 || script[1] == 0x03)) {
@@ -45,24 +53,24 @@ bool CScriptCompressor::IsToPubKey(CPubKey &pubkey) const
     return false;
 }
 
-bool CScriptCompressor::Compress(std::vector<unsigned char> &out) const
+bool CompressScript(const CScript& script, std::vector<unsigned char> &out)
 {
     CKeyID keyID;
-    if (IsToKeyID(keyID)) {
+    if (IsToKeyID(script, keyID)) {
         out.resize(21);
         out[0] = 0x00;
         memcpy(&out[1], &keyID, 20);
         return true;
     }
     CScriptID scriptID;
-    if (IsToScriptID(scriptID)) {
+    if (IsToScriptID(script, scriptID)) {
         out.resize(21);
         out[0] = 0x01;
         memcpy(&out[1], &scriptID, 20);
         return true;
     }
     CPubKey pubkey;
-    if (IsToPubKey(pubkey)) {
+    if (IsToPubKey(script, pubkey)) {
         out.resize(33);
         memcpy(&out[1], &pubkey[1], 32);
         if (pubkey[0] == 0x02 || pubkey[0] == 0x03) {
@@ -76,7 +84,7 @@ bool CScriptCompressor::Compress(std::vector<unsigned char> &out) const
     return false;
 }
 
-unsigned int CScriptCompressor::GetSpecialSize(unsigned int nSize) const
+unsigned int GetSpecialScriptSize(unsigned int nSize)
 {
     if (nSize == 0 || nSize == 1)
         return 20;
@@ -85,7 +93,7 @@ unsigned int CScriptCompressor::GetSpecialSize(unsigned int nSize) const
     return 0;
 }
 
-bool CScriptCompressor::Decompress(unsigned int nSize, const std::vector<unsigned char> &in)
+bool DecompressScript(CScript& script, unsigned int nSize, const std::vector<unsigned char> &in)
 {
     switch(nSize) {
     case 0x00:
@@ -139,7 +147,7 @@ bool CScriptCompressor::Decompress(unsigned int nSize, const std::vector<unsigne
 // * if e==9, we only know the resulting number is not zero, so output 1 + 10*(n - 1) + 9
 // (this is decodable, as d is in [1-9] and e is in [0-9])
 
-uint64_t CTxOutCompressor::CompressAmount(uint64_t n)
+uint64_t CompressAmount(uint64_t n)
 {
     if (n == 0)
         return 0;
@@ -158,7 +166,7 @@ uint64_t CTxOutCompressor::CompressAmount(uint64_t n)
     }
 }
 
-uint64_t CTxOutCompressor::DecompressAmount(uint64_t x)
+uint64_t DecompressAmount(uint64_t x)
 {
     // x = 0  OR  x = 1+10*(9*n + d - 1) + e  OR  x = 1+10*(n - 1) + 9
     if (x == 0)
diff --git a/src/compressor.h b/src/compressor.h
index 6fcecd27e9..561c8e66d0 100644
--- a/src/compressor.h
+++ b/src/compressor.h
@@ -14,6 +14,13 @@ class CKeyID;
 class CPubKey;
 class CScriptID;
 
+bool CompressScript(const CScript& script, std::vector<unsigned char> &out);
+unsigned int GetSpecialScriptSize(unsigned int nSize);
+bool DecompressScript(CScript& script, unsigned int nSize, const std::vector<unsigned char> &out);
+
+uint64_t CompressAmount(uint64_t nAmount);
+uint64_t DecompressAmount(uint64_t nAmount);
+
 /** Compact serializer for scripts.
  *
  *  It detects common cases and encodes them much more efficiently.
@@ -37,28 +44,13 @@ private:
     static const unsigned int nSpecialScripts = 6;
 
     CScript &script;
-protected:
-    /**
-     * These check for scripts for which a special case with a shorter encoding is defined.
-     * They are implemented separately from the CScript test, as these test for exact byte
-     * sequence correspondences, and are more strict. For example, IsToPubKey also verifies
-     * whether the public key is valid (as invalid ones cannot be represented in compressed
-     * form).
-     */
-    bool IsToKeyID(CKeyID &hash) const;
-    bool IsToScriptID(CScriptID &hash) const;
-    bool IsToPubKey(CPubKey &pubkey) const;
-
-    bool Compress(std::vector<unsigned char> &out) const;
-    unsigned int GetSpecialSize(unsigned int nSize) const;
-    bool Decompress(unsigned int nSize, const std::vector<unsigned char> &out);
 public:
     explicit CScriptCompressor(CScript &scriptIn) : script(scriptIn) { }
 
     template<typename Stream>
     void Serialize(Stream &s) const {
         std::vector<unsigned char> compr;
-        if (Compress(compr)) {
+        if (CompressScript(script, compr)) {
             s << CFlatData(compr);
             return;
         }
@@ -72,9 +64,9 @@ public:
         unsigned int nSize = 0;
         s >> VARINT(nSize);
         if (nSize < nSpecialScripts) {
-            std::vector<unsigned char> vch(GetSpecialSize(nSize), 0x00);
+            std::vector<unsigned char> vch(GetSpecialScriptSize(nSize), 0x00);
             s >> CFlatData(vch);
-            Decompress(nSize, vch);
+            DecompressScript(script, nSize, vch);
             return;
         }
         nSize -= nSpecialScripts;
@@ -96,9 +88,6 @@ private:
     CTxOut &txout;
 
 public:
-    static uint64_t CompressAmount(uint64_t nAmount);
-    static uint64_t DecompressAmount(uint64_t nAmount);
-
     explicit CTxOutCompressor(CTxOut &txoutIn) : txout(txoutIn) { }
 
     ADD_SERIALIZE_METHODS;
diff --git a/src/dbwrapper.cpp b/src/dbwrapper.cpp
index fb0d4215a2..752f985bc0 100644
--- a/src/dbwrapper.cpp
+++ b/src/dbwrapper.cpp
@@ -71,6 +71,31 @@ public:
     }
 };
 
+static void SetMaxOpenFiles(leveldb::Options *options) {
+    // On most platforms the default setting of max_open_files (which is 1000)
+    // is optimal. On Windows using a large file count is OK because the handles
+    // do not interfere with select() loops. On 64-bit Unix hosts this value is
+    // also OK, because up to that amount LevelDB will use an mmap
+    // implementation that does not use extra file descriptors (the fds are
+    // closed after being mmaped).
+    //
+    // Increasing the value beyond the default is dangerous because LevelDB will
+    // fall back to a non-mmap implementation when the file count is too large.
+    // On 32-bit Unix host we should decrease the value because the handles use
+    // up real fds, and we want to avoid fd exhaustion issues.
+    //
+    // See PR #12495 for further discussion.
+
+    int default_open_files = options->max_open_files;
+#ifndef WIN32
+    if (sizeof(void*) < 8) {
+        options->max_open_files = 64;
+    }
+#endif
+    LogPrint(BCLog::LEVELDB, "LevelDB using max_open_files=%d (default=%d)\n",
+             options->max_open_files, default_open_files);
+}
+
 static leveldb::Options GetOptions(size_t nCacheSize)
 {
     leveldb::Options options;
@@ -78,13 +103,13 @@ static leveldb::Options GetOptions(size_t nCacheSize)
     options.write_buffer_size = nCacheSize / 4; // up to two write buffers may be held in memory simultaneously
     options.filter_policy = leveldb::NewBloomFilterPolicy(10);
     options.compression = leveldb::kNoCompression;
-    options.max_open_files = 64;
     options.info_log = new CBitcoinLevelDBLogger();
     if (leveldb::kMajorVersion > 1 || (leveldb::kMajorVersion == 1 && leveldb::kMinorVersion >= 16)) {
         // LevelDB versions before 1.16 consider short writes to be corruption. Only trigger error
         // on corruption in later versions.
         options.paranoid_checks = true;
     }
+    SetMaxOpenFiles(&options);
     return options;
 }
 
@@ -159,12 +184,12 @@ bool CDBWrapper::WriteBatch(CDBBatch& batch, bool fSync)
     const bool log_memory = LogAcceptCategory(BCLog::LEVELDB);
     double mem_before = 0;
     if (log_memory) {
-        mem_before = DynamicMemoryUsage() / 1024 / 1024;
+        mem_before = DynamicMemoryUsage() / 1024.0 / 1024;
     }
     leveldb::Status status = pdb->Write(fSync ? syncoptions : writeoptions, &batch.batch);
     dbwrapper_private::HandleError(status);
     if (log_memory) {
-        double mem_after = DynamicMemoryUsage() / 1024 / 1024;
+        double mem_after = DynamicMemoryUsage() / 1024.0 / 1024;
         LogPrint(BCLog::LEVELDB, "WriteBatch memory usage: db=%s, before=%.1fMiB, after=%.1fMiB\n",
                  m_name, mem_before, mem_after);
     }
diff --git a/src/init.cpp b/src/init.cpp
index b0ba0cb835..f6f522da66 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -43,10 +43,8 @@
 #include <util.h>
 #include <utilmoneystr.h>
 #include <validationinterface.h>
-#ifdef ENABLE_WALLET
-#include <wallet/init.h>
-#endif
 #include <warnings.h>
+#include <walletinitinterface.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <memory>
@@ -74,6 +72,7 @@ static const bool DEFAULT_STOPAFTERBLOCKIMPORT = false;
 
 std::unique_ptr<CConnman> g_connman;
 std::unique_ptr<PeerLogicValidation> peerLogic;
+std::unique_ptr<WalletInitInterface> g_wallet_init_interface;
 
 #if ENABLE_ZMQ
 static CZMQNotificationInterface* pzmqNotificationInterface = nullptr;
@@ -116,7 +115,6 @@ static const char* FEE_ESTIMATES_FILENAME="fee_estimates.dat";
 //
 
 std::atomic<bool> fRequestShutdown(false);
-std::atomic<bool> fDumpMempoolLater(false);
 
 void StartShutdown()
 {
@@ -189,9 +187,7 @@ void Shutdown()
     StopREST();
     StopRPC();
     StopHTTPServer();
-#ifdef ENABLE_WALLET
-    FlushWallets();
-#endif
+    g_wallet_init_interface->Flush();
     StopMapPort();
 
     // Because these depend on each-other, we make sure that neither can be
@@ -208,7 +204,7 @@ void Shutdown()
     threadGroup.interrupt_all();
     threadGroup.join_all();
 
-    if (fDumpMempoolLater && gArgs.GetArg("-persistmempool", DEFAULT_PERSIST_MEMPOOL)) {
+    if (g_is_mempool_loaded && gArgs.GetArg("-persistmempool", DEFAULT_PERSIST_MEMPOOL)) {
         DumpMempool();
     }
 
@@ -249,9 +245,7 @@ void Shutdown()
         pcoinsdbview.reset();
         pblocktree.reset();
     }
-#ifdef ENABLE_WALLET
-    StopWallets();
-#endif
+    g_wallet_init_interface->Stop();
 
 #if ENABLE_ZMQ
     if (pzmqNotificationInterface) {
@@ -271,9 +265,8 @@ void Shutdown()
     UnregisterAllValidationInterfaces();
     GetMainSignals().UnregisterBackgroundSignalScheduler();
     GetMainSignals().UnregisterWithMempoolSignals(mempool);
-#ifdef ENABLE_WALLET
-    CloseWallets();
-#endif
+    g_wallet_init_interface->Close();
+    g_wallet_init_interface.reset();
     globalVerifyHandle.reset();
     ECC_Stop();
     LogPrintf("%s: done\n", __func__);
@@ -416,9 +409,7 @@ std::string HelpMessage(HelpMessageMode mode)
     strUsage += HelpMessageOpt("-whitelist=<IP address or network>", _("Whitelist peers connecting from the given IP address (e.g. 1.2.3.4) or CIDR notated network (e.g. 1.2.3.0/24). Can be specified multiple times.") +
         " " + _("Whitelisted peers cannot be DoS banned and their transactions are always relayed, even if they are already in the mempool, useful e.g. for a gateway"));
 
-#ifdef ENABLE_WALLET
-    strUsage += GetWalletHelpString(showDebug);
-#endif
+    strUsage += g_wallet_init_interface->GetHelpString(showDebug);
 
 #if ENABLE_ZMQ
     strUsage += HelpMessageGroup(_("ZeroMQ notification options:"));
@@ -429,8 +420,7 @@ std::string HelpMessage(HelpMessageMode mode)
 #endif
 
     strUsage += HelpMessageGroup(_("Debugging/Testing options:"));
-    if (showDebug)
-    {
+    if (showDebug) {
         strUsage += HelpMessageOpt("-checkblocks=<n>", strprintf(_("How many blocks to check at startup (default: %u, 0 = all)"), DEFAULT_CHECKBLOCKS));
         strUsage += HelpMessageOpt("-checklevel=<n>", strprintf(_("How thorough the block verification of -checkblocks is (0-4, default: %u)"), DEFAULT_CHECKLEVEL));
         strUsage += HelpMessageOpt("-checkblockindex", strprintf("Do a full consistency check for mapBlockIndex, setBlockIndexCandidates, chainActive and mapBlocksUnlinked occasionally. (default: %u)", defaultChainParams->DefaultConsistencyChecks()));
@@ -440,7 +430,6 @@ std::string HelpMessage(HelpMessageMode mode)
         strUsage += HelpMessageOpt("-deprecatedrpc=<method>", "Allows deprecated RPC method(s) to be used");
         strUsage += HelpMessageOpt("-testsafemode", strprintf("Force safe mode (default: %u)", DEFAULT_TESTSAFEMODE));
         strUsage += HelpMessageOpt("-dropmessagestest=<n>", "Randomly drop 1 of every <n> network messages");
-        strUsage += HelpMessageOpt("-fuzzmessagestest=<n>", "Randomly fuzz 1 of every <n> network messages");
         strUsage += HelpMessageOpt("-stopafterblockimport", strprintf("Stop running after importing blocks from disk (default: %u)", DEFAULT_STOPAFTERBLOCKIMPORT));
         strUsage += HelpMessageOpt("-stopatheight", strprintf("Stop running after reaching the given height in the main chain (default: %u)", DEFAULT_STOPATHEIGHT));
 
@@ -692,8 +681,8 @@ void ThreadImport(std::vector<fs::path> vImportFiles)
     } // End scope of CImportingNow
     if (gArgs.GetArg("-persistmempool", DEFAULT_PERSIST_MEMPOOL)) {
         LoadMempool();
-        fDumpMempoolLater = !fRequestShutdown;
     }
+    g_is_mempool_loaded = !fRequestShutdown;
 }
 
 /** Sanity checks
@@ -1087,10 +1076,7 @@ bool AppInitParameterInteraction()
         return InitError(strprintf("acceptnonstdtxn is not currently supported for %s chain", chainparams.NetworkIDString()));
     nBytesPerSigOp = gArgs.GetArg("-bytespersigop", nBytesPerSigOp);
 
-#ifdef ENABLE_WALLET
-    if (!WalletParameterInteraction())
-        return false;
-#endif
+    if (!g_wallet_init_interface->ParameterInteraction()) return false;
 
     fIsBareMultisigStd = gArgs.GetBoolArg("-permitbaremultisig", DEFAULT_PERMIT_BAREMULTISIG);
     fAcceptDatacarrier = gArgs.GetBoolArg("-datacarrier", DEFAULT_ACCEPT_DATACARRIER);
@@ -1256,9 +1242,7 @@ bool AppInitMain()
      * available in the GUI RPC console even if external calls are disabled.
      */
     RegisterAllCoreRPCCommands(tableRPC);
-#ifdef ENABLE_WALLET
-    RegisterWalletRPC(tableRPC);
-#endif
+    g_wallet_init_interface->RegisterRPC(tableRPC);
 
     /* Start the RPC server already.  It will be started in "warmup" mode
      * and not really process calls already (but it will signify connections
@@ -1275,10 +1259,8 @@ bool AppInitMain()
     int64_t nStart;
 
     // ********************************************************* Step 5: verify wallet database integrity
-#ifdef ENABLE_WALLET
-    if (!VerifyWallets())
-        return false;
-#endif
+    if (!g_wallet_init_interface->Verify()) return false;
+
     // ********************************************************* Step 6: network initialization
     // Note that we absolutely cannot open any actual connections
     // until the very end ("start node") as the UTXO/block state
@@ -1596,12 +1578,7 @@ bool AppInitMain()
     fFeeEstimatesInitialized = true;
 
     // ********************************************************* Step 8: load wallet
-#ifdef ENABLE_WALLET
-    if (!OpenWallets())
-        return false;
-#else
-    LogPrintf("No wallet support compiled in!\n");
-#endif
+    if (!g_wallet_init_interface->Open()) return false;
 
     // ********************************************************* Step 9: data directory maintenance
 
@@ -1747,9 +1724,7 @@ bool AppInitMain()
     SetRPCWarmupFinished();
     uiInterface.InitMessage(_("Done loading"));
 
-#ifdef ENABLE_WALLET
-    StartWallets(scheduler);
-#endif
+    g_wallet_init_interface->Start(scheduler);
 
     return true;
 }
diff --git a/src/init.h b/src/init.h
index 6f75a43e62..c93a210154 100644
--- a/src/init.h
+++ b/src/init.h
@@ -6,11 +6,15 @@
 #ifndef BITCOIN_INIT_H
 #define BITCOIN_INIT_H
 
+#include <memory>
 #include <string>
 
 class CScheduler;
 class CWallet;
 
+class WalletInitInterface;
+extern std::unique_ptr<WalletInitInterface> g_wallet_init_interface;
+
 namespace boost
 {
 class thread_group;
diff --git a/src/netaddress.h b/src/netaddress.h
index 93bbb66491..ad6b55eb58 100644
--- a/src/netaddress.h
+++ b/src/netaddress.h
@@ -93,7 +93,7 @@ class CNetAddr
 
         template <typename Stream, typename Operation>
         inline void SerializationOp(Stream& s, Operation ser_action) {
-            READWRITE(FLATDATA(ip));
+            READWRITE(ip);
         }
 
         friend class CSubNet;
@@ -131,8 +131,8 @@ class CSubNet
         template <typename Stream, typename Operation>
         inline void SerializationOp(Stream& s, Operation ser_action) {
             READWRITE(network);
-            READWRITE(FLATDATA(netmask));
-            READWRITE(FLATDATA(valid));
+            READWRITE(netmask);
+            READWRITE(valid);
         }
 };
 
@@ -166,7 +166,7 @@ class CService : public CNetAddr
 
         template <typename Stream, typename Operation>
         inline void SerializationOp(Stream& s, Operation ser_action) {
-            READWRITE(FLATDATA(ip));
+            READWRITE(ip);
             unsigned short portN = htons(port);
             READWRITE(FLATDATA(portN));
             if (ser_action.ForRead())
diff --git a/src/protocol.h b/src/protocol.h
index e518d11944..a07c5ea862 100644
--- a/src/protocol.h
+++ b/src/protocol.h
@@ -48,10 +48,10 @@ public:
     template <typename Stream, typename Operation>
     inline void SerializationOp(Stream& s, Operation ser_action)
     {
-        READWRITE(FLATDATA(pchMessageStart));
-        READWRITE(FLATDATA(pchCommand));
+        READWRITE(pchMessageStart);
+        READWRITE(pchCommand);
         READWRITE(nMessageSize);
-        READWRITE(FLATDATA(pchChecksum));
+        READWRITE(pchChecksum);
     }
 
     char pchMessageStart[MESSAGE_START_SIZE];
diff --git a/src/qt/bitcoin.cpp b/src/qt/bitcoin.cpp
index f1298df8ca..f853c04617 100644
--- a/src/qt/bitcoin.cpp
+++ b/src/qt/bitcoin.cpp
@@ -34,8 +34,10 @@
 #include <warnings.h>
 
 #ifdef ENABLE_WALLET
+#include <wallet/init.h>
 #include <wallet/wallet.h>
 #endif
+#include <walletinitinterface.h>
 
 #include <stdint.h>
 
@@ -677,6 +679,11 @@ int main(int argc, char *argv[])
     // Start up the payment server early, too, so impatient users that click on
     // bitcoin: links repeatedly have their payment requests routed to this process:
     app.createPaymentServer();
+
+    // Hook up the wallet init interface
+    g_wallet_init_interface.reset(new WalletInit);
+#else
+    g_wallet_init_interface.reset(new DummyWalletInit);
 #endif
 
     /// 9. Main GUI initialization
diff --git a/src/qt/recentrequeststablemodel.cpp b/src/qt/recentrequeststablemodel.cpp
index 0dd7d46960..f045053c3b 100644
--- a/src/qt/recentrequeststablemodel.cpp
+++ b/src/qt/recentrequeststablemodel.cpp
@@ -139,10 +139,9 @@ bool RecentRequestsTableModel::removeRows(int row, int count, const QModelIndex
 
     if(count > 0 && row >= 0 && (row+count) <= list.size())
     {
-        const RecentRequestEntry *rec;
         for (int i = 0; i < count; ++i)
         {
-            rec = &list[row+i];
+            const RecentRequestEntry* rec = &list[row+i];
             if (!walletModel->saveReceiveRequest(rec->recipient.address.toStdString(), rec->id, ""))
                 return false;
         }
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index e15dad2f0b..31cbec4c86 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -1607,13 +1607,17 @@ UniValue savemempool(const JSONRPCRequest& request)
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(
             "savemempool\n"
-            "\nDumps the mempool to disk.\n"
+            "\nDumps the mempool to disk. It will fail until the previous dump is fully loaded.\n"
             "\nExamples:\n"
             + HelpExampleCli("savemempool", "")
             + HelpExampleRpc("savemempool", "")
         );
     }
 
+    if (!g_is_mempool_loaded) {
+        throw JSONRPCError(RPC_MISC_ERROR, "The mempool was not loaded yet");
+    }
+
     if (!DumpMempool()) {
         throw JSONRPCError(RPC_MISC_ERROR, "Unable to dump mempool to disk");
     }
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 20bfd3f355..77040f75fd 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -1023,18 +1023,18 @@ UniValue signrawtransaction(const JSONRPCRequest& request)
         new_request.params.push_back(request.params[1]);
         new_request.params.push_back(request.params[3]);
         return signrawtransactionwithkey(new_request);
-    }
-    // Otherwise sign with the wallet which does not take a privkeys parameter
+    } else {
 #ifdef ENABLE_WALLET
-    else {
+        // Otherwise sign with the wallet which does not take a privkeys parameter
         new_request.params.push_back(request.params[0]);
         new_request.params.push_back(request.params[1]);
         new_request.params.push_back(request.params[3]);
         return signrawtransactionwithwallet(new_request);
-    }
+#else
+        // If we have made it this far, then wallet is disabled and no private keys were given, so fail here.
+        throw JSONRPCError(RPC_INVALID_PARAMETER, "No private keys available.");
 #endif
-    // If we have made it this far, then wallet is disabled and no private keys were given, so fail here.
-    throw JSONRPCError(RPC_INVALID_PARAMETER, "No private keys available.");
+    }
 }
 
 UniValue sendrawtransaction(const JSONRPCRequest& request)
diff --git a/src/serialize.h b/src/serialize.h
index 91da6b0f80..247e915298 100644
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -59,6 +59,12 @@ inline T* NCONST_PTR(const T* val)
     return const_cast<T*>(val);
 }
 
+//! Safely convert odd char pointer types to standard ones.
+inline char* CharCast(char* c) { return c; }
+inline char* CharCast(unsigned char* c) { return (char*)c; }
+inline const char* CharCast(const char* c) { return c; }
+inline const char* CharCast(const unsigned char* c) { return (const char*)c; }
+
 /*
  * Lowest-level serialization and conversion.
  * @note Sizes of these types are verified in the tests
@@ -177,6 +183,8 @@ template<typename Stream> inline void Serialize(Stream& s, int64_t a ) { ser_wri
 template<typename Stream> inline void Serialize(Stream& s, uint64_t a) { ser_writedata64(s, a); }
 template<typename Stream> inline void Serialize(Stream& s, float a   ) { ser_writedata32(s, ser_float_to_uint32(a)); }
 template<typename Stream> inline void Serialize(Stream& s, double a  ) { ser_writedata64(s, ser_double_to_uint64(a)); }
+template<typename Stream, int N> inline void Serialize(Stream& s, const char (&a)[N]) { s.write(a, N); }
+template<typename Stream, int N> inline void Serialize(Stream& s, const unsigned char (&a)[N]) { s.write(CharCast(a), N); }
 
 template<typename Stream> inline void Unserialize(Stream& s, char& a    ) { a = ser_readdata8(s); } // TODO Get rid of bare char
 template<typename Stream> inline void Unserialize(Stream& s, int8_t& a  ) { a = ser_readdata8(s); }
@@ -189,6 +197,8 @@ template<typename Stream> inline void Unserialize(Stream& s, int64_t& a ) { a =
 template<typename Stream> inline void Unserialize(Stream& s, uint64_t& a) { a = ser_readdata64(s); }
 template<typename Stream> inline void Unserialize(Stream& s, float& a   ) { a = ser_uint32_to_float(ser_readdata32(s)); }
 template<typename Stream> inline void Unserialize(Stream& s, double& a  ) { a = ser_uint64_to_double(ser_readdata64(s)); }
+template<typename Stream, int N> inline void Unserialize(Stream& s, char (&a)[N]) { s.read(a, N); }
+template<typename Stream, int N> inline void Unserialize(Stream& s, unsigned char (&a)[N]) { s.read(CharCast(a), N); }
 
 template<typename Stream> inline void Serialize(Stream& s, bool a)    { char f=a; ser_writedata8(s, f); }
 template<typename Stream> inline void Unserialize(Stream& s, bool& a) { char f=ser_readdata8(s); a=f; }
diff --git a/src/test/compress_tests.cpp b/src/test/compress_tests.cpp
index 3c26013622..127cc154df 100644
--- a/src/test/compress_tests.cpp
+++ b/src/test/compress_tests.cpp
@@ -25,16 +25,16 @@
 BOOST_FIXTURE_TEST_SUITE(compress_tests, BasicTestingSetup)
 
 bool static TestEncode(uint64_t in) {
-    return in == CTxOutCompressor::DecompressAmount(CTxOutCompressor::CompressAmount(in));
+    return in == DecompressAmount(CompressAmount(in));
 }
 
 bool static TestDecode(uint64_t in) {
-    return in == CTxOutCompressor::CompressAmount(CTxOutCompressor::DecompressAmount(in));
+    return in == CompressAmount(DecompressAmount(in));
 }
 
 bool static TestPair(uint64_t dec, uint64_t enc) {
-    return CTxOutCompressor::CompressAmount(dec) == enc &&
-           CTxOutCompressor::DecompressAmount(enc) == dec;
+    return CompressAmount(dec) == enc &&
+           DecompressAmount(enc) == dec;
 }
 
 BOOST_AUTO_TEST_CASE(compress_amounts)
diff --git a/src/test/net_tests.cpp b/src/test/net_tests.cpp
index e03234060d..6552613c04 100644
--- a/src/test/net_tests.cpp
+++ b/src/test/net_tests.cpp
@@ -64,7 +64,7 @@ public:
 CDataStream AddrmanToStream(CAddrManSerializationMock& _addrman)
 {
     CDataStream ssPeersIn(SER_DISK, CLIENT_VERSION);
-    ssPeersIn << FLATDATA(Params().MessageStart());
+    ssPeersIn << Params().MessageStart();
     ssPeersIn << _addrman;
     std::string str = ssPeersIn.str();
     std::vector<unsigned char> vchData(str.begin(), str.end());
@@ -110,7 +110,7 @@ BOOST_AUTO_TEST_CASE(caddrdb_read)
     BOOST_CHECK(addrman1.size() == 0);
     try {
         unsigned char pchMsgTmp[4];
-        ssPeers1 >> FLATDATA(pchMsgTmp);
+        ssPeers1 >> pchMsgTmp;
         ssPeers1 >> addrman1;
     } catch (const std::exception& e) {
         exceptionThrown = true;
@@ -142,7 +142,7 @@ BOOST_AUTO_TEST_CASE(caddrdb_read_corrupted)
     BOOST_CHECK(addrman1.size() == 0);
     try {
         unsigned char pchMsgTmp[4];
-        ssPeers1 >> FLATDATA(pchMsgTmp);
+        ssPeers1 >> pchMsgTmp;
         ssPeers1 >> addrman1;
     } catch (const std::exception& e) {
         exceptionThrown = true;
diff --git a/src/test/serialize_tests.cpp b/src/test/serialize_tests.cpp
index 7a79a77e8b..9b8b7bdc56 100644
--- a/src/test/serialize_tests.cpp
+++ b/src/test/serialize_tests.cpp
@@ -19,11 +19,15 @@ protected:
     int intval;
     bool boolval;
     std::string stringval;
-    const char* charstrval;
+    char charstrval[16];
     CTransactionRef txval;
 public:
     CSerializeMethodsTestSingle() = default;
-    CSerializeMethodsTestSingle(int intvalin, bool boolvalin, std::string stringvalin, const char* charstrvalin, CTransaction txvalin) : intval(intvalin), boolval(boolvalin), stringval(std::move(stringvalin)), charstrval(charstrvalin), txval(MakeTransactionRef(txvalin)){}
+    CSerializeMethodsTestSingle(int intvalin, bool boolvalin, std::string stringvalin, const char* charstrvalin, CTransaction txvalin) : intval(intvalin), boolval(boolvalin), stringval(std::move(stringvalin)), txval(MakeTransactionRef(txvalin))
+    {
+        memcpy(charstrval, charstrvalin, sizeof(charstrval));
+    }
+
     ADD_SERIALIZE_METHODS;
 
     template <typename Stream, typename Operation>
@@ -31,7 +35,7 @@ public:
         READWRITE(intval);
         READWRITE(boolval);
         READWRITE(stringval);
-        READWRITE(FLATDATA(charstrval));
+        READWRITE(charstrval);
         READWRITE(txval);
     }
 
@@ -53,7 +57,7 @@ public:
 
     template <typename Stream, typename Operation>
     inline void SerializationOp(Stream& s, Operation ser_action) {
-        READWRITE(intval, boolval, stringval, FLATDATA(charstrval), txval);
+        READWRITE(intval, boolval, stringval, charstrval, txval);
     }
 };
 
@@ -344,7 +348,7 @@ BOOST_AUTO_TEST_CASE(class_methods)
     int intval(100);
     bool boolval(true);
     std::string stringval("testing");
-    const char* charstrval("testing charstr");
+    const char charstrval[16] = "testing charstr";
     CMutableTransaction txval;
     CSerializeMethodsTestSingle methodtest1(intval, boolval, stringval, charstrval, txval);
     CSerializeMethodsTestMany methodtest2(intval, boolval, stringval, charstrval, txval);
@@ -360,7 +364,7 @@ BOOST_AUTO_TEST_CASE(class_methods)
     BOOST_CHECK(methodtest2 == methodtest3);
     BOOST_CHECK(methodtest3 == methodtest4);
 
-    CDataStream ss2(SER_DISK, PROTOCOL_VERSION, intval, boolval, stringval, FLATDATA(charstrval), txval);
+    CDataStream ss2(SER_DISK, PROTOCOL_VERSION, intval, boolval, stringval, charstrval, txval);
     ss2 >> methodtest3;
     BOOST_CHECK(methodtest3 == methodtest4);
 }
diff --git a/src/test/streams_tests.cpp b/src/test/streams_tests.cpp
index 1108dab584..5d057108b1 100644
--- a/src/test/streams_tests.cpp
+++ b/src/test/streams_tests.cpp
@@ -57,16 +57,16 @@ BOOST_AUTO_TEST_CASE(streams_vector_writer)
     BOOST_CHECK((vch == std::vector<unsigned char>{{0, 0, 0, 0, 1, 2}}));
     vch.clear();
 
-    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 0, FLATDATA(bytes));
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 0, bytes);
     BOOST_CHECK((vch == std::vector<unsigned char>{{3, 4, 5, 6}}));
-    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 0, FLATDATA(bytes));
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 0, bytes);
     BOOST_CHECK((vch == std::vector<unsigned char>{{3, 4, 5, 6}}));
     vch.clear();
 
     vch.resize(4, 8);
-    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 2, a, FLATDATA(bytes), b);
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 2, a, bytes, b);
     BOOST_CHECK((vch == std::vector<unsigned char>{{8, 8, 1, 3, 4, 5, 6, 2}}));
-    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 2, a, FLATDATA(bytes), b);
+    CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 2, a, bytes, b);
     BOOST_CHECK((vch == std::vector<unsigned char>{{8, 8, 1, 3, 4, 5, 6, 2}}));
     vch.clear();
 }
diff --git a/src/test/test_bitcoin.cpp b/src/test/test_bitcoin.cpp
index 95c4825b84..9390a93b99 100644
--- a/src/test/test_bitcoin.cpp
+++ b/src/test/test_bitcoin.cpp
@@ -145,9 +145,9 @@ TestChain100Setup::CreateAndProcessBlock(const std::vector<CMutableTransaction>&
     for (const CMutableTransaction& tx : txns)
         block.vtx.push_back(MakeTransactionRef(tx));
     // IncrementExtraNonce creates a valid coinbase and merkleRoot
-    unsigned int extraNonce = 0;
     {
         LOCK(cs_main);
+        unsigned int extraNonce = 0;
         IncrementExtraNonce(&block, chainActive.Tip(), extraNonce);
     }
 
diff --git a/src/test/util_tests.cpp b/src/test/util_tests.cpp
index 053ec92ca5..4b44bbadac 100644
--- a/src/test/util_tests.cpp
+++ b/src/test/util_tests.cpp
@@ -746,9 +746,8 @@ static constexpr char ExitCommand = 'X';
 static void TestOtherProcess(fs::path dirname, std::string lockname, int fd)
 {
     char ch;
-    int rv;
     while (true) {
-        rv = read(fd, &ch, 1); // Wait for command
+        int rv = read(fd, &ch, 1); // Wait for command
         assert(rv == 1);
         switch(ch) {
         case LockCommand:
diff --git a/src/validation.cpp b/src/validation.cpp
index d107fec70c..77764ff923 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -227,6 +227,7 @@ CAmount maxTxFee = DEFAULT_TRANSACTION_MAXFEE;
 
 CBlockPolicyEstimator feeEstimator;
 CTxMemPool mempool(&feeEstimator);
+std::atomic_bool g_is_mempool_loaded{false};
 
 /** Constant stuff for coinbase transactions we create: */
 CScript COINBASE_FLAGS;
@@ -1077,7 +1078,7 @@ static bool WriteBlockToDisk(const CBlock& block, CDiskBlockPos& pos, const CMes
 
     // Write index header
     unsigned int nSize = GetSerializeSize(fileout, block);
-    fileout << FLATDATA(messageStart) << nSize;
+    fileout << messageStart << nSize;
 
     // Write block
     long fileOutPos = ftell(fileout.Get());
@@ -1441,7 +1442,7 @@ bool UndoWriteToDisk(const CBlockUndo& blockundo, CDiskBlockPos& pos, const uint
 
     // Write index header
     unsigned int nSize = GetSerializeSize(fileout, blockundo);
-    fileout << FLATDATA(messageStart) << nSize;
+    fileout << messageStart << nSize;
 
     // Write undo data
     long fileOutPos = ftell(fileout.Get());
@@ -3223,10 +3224,10 @@ static bool ContextualCheckBlock(const CBlock& block, CValidationState& state, c
     // Validation for witness commitments.
     // * We compute the witness hash (which is the hash including witnesses) of all the block's transactions, except the
     //   coinbase (where 0x0000....0000 is used instead).
-    // * The coinbase scriptWitness is a stack of a single 32-byte vector, containing a witness nonce (unconstrained).
+    // * The coinbase scriptWitness is a stack of a single 32-byte vector, containing a witness reserved value (unconstrained).
     // * We build a merkle tree with all those witness hashes as leaves (similar to the hashMerkleRoot in the block header).
     // * There must be at least one output whose scriptPubKey is a single 36-byte push, the first 4 bytes of which are
-    //   {0xaa, 0x21, 0xa9, 0xed}, and the following 32 bytes are SHA256^2(witness root, witness nonce). In case there are
+    //   {0xaa, 0x21, 0xa9, 0xed}, and the following 32 bytes are SHA256^2(witness root, witness reserved value). In case there are
     //   multiple, the last one is used.
     bool fHaveWitness = false;
     if (VersionBitsState(pindexPrev, consensusParams, Consensus::DEPLOYMENT_SEGWIT, versionbitscache) == ThresholdState::ACTIVE) {
@@ -3238,7 +3239,7 @@ static bool ContextualCheckBlock(const CBlock& block, CValidationState& state, c
             // already does not permit it, it is impossible to trigger in the
             // witness tree.
             if (block.vtx[0]->vin[0].scriptWitness.stack.size() != 1 || block.vtx[0]->vin[0].scriptWitness.stack[0].size() != 32) {
-                return state.DoS(100, false, REJECT_INVALID, "bad-witness-nonce-size", true, strprintf("%s : invalid witness nonce size", __func__));
+                return state.DoS(100, false, REJECT_INVALID, "bad-witness-nonce-size", true, strprintf("%s : invalid witness reserved value size", __func__));
             }
             CHash256().Write(hashWitness.begin(), 32).Write(&block.vtx[0]->vin[0].scriptWitness.stack[0][0], 32).Finalize(hashWitness.begin());
             if (memcmp(hashWitness.begin(), &block.vtx[0]->vout[commitpos].scriptPubKey[6], 32)) {
@@ -3257,7 +3258,7 @@ static bool ContextualCheckBlock(const CBlock& block, CValidationState& state, c
         }
     }
 
-    // After the coinbase witness nonce and commitment are verified,
+    // After the coinbase witness reserved value and commitment are verified,
     // we can check if the block weight passes (before we've checked the
     // coinbase witness, it would be possible for the weight to be too
     // large by filling up the coinbase witness, which doesn't change
@@ -4283,7 +4284,7 @@ bool LoadExternalBlockFile(const CChainParams& chainparams, FILE* fileIn, CDiskB
                 unsigned char buf[CMessageHeader::MESSAGE_START_SIZE];
                 blkdat.FindByte(chainparams.MessageStart()[0]);
                 nRewind = blkdat.GetPos()+1;
-                blkdat >> FLATDATA(buf);
+                blkdat >> buf;
                 if (memcmp(buf, chainparams.MessageStart(), CMessageHeader::MESSAGE_START_SIZE))
                     continue;
                 // read size
diff --git a/src/validation.h b/src/validation.h
index 4596879771..4031989f00 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -158,6 +158,7 @@ extern CScript COINBASE_FLAGS;
 extern CCriticalSection cs_main;
 extern CBlockPolicyEstimator feeEstimator;
 extern CTxMemPool mempool;
+extern std::atomic_bool g_is_mempool_loaded;
 typedef std::unordered_map<uint256, CBlockIndex*, BlockHasher> BlockMap;
 extern BlockMap& mapBlockIndex;
 extern uint64_t nLastBlockTx;
@@ -411,7 +412,7 @@ bool IsWitnessEnabled(const CBlockIndex* pindexPrev, const Consensus::Params& pa
 /** When there are blocks in the active chain with missing data, rewind the chainstate and remove them from the block index */
 bool RewindBlockIndex(const CChainParams& params);
 
-/** Update uncommitted block structures (currently: only the witness nonce). This is safe for submitted blocks. */
+/** Update uncommitted block structures (currently: only the witness reserved value). This is safe for submitted blocks. */
 void UpdateUncommittedBlockStructures(CBlock& block, const CBlockIndex* pindexPrev, const Consensus::Params& consensusParams);
 
 /** Produce the necessary coinbase commitment for a block (modifies the hash, don't call for mined blocks). */
diff --git a/src/wallet/init.cpp b/src/wallet/init.cpp
index 61481e01b6..3d7bb674f0 100644
--- a/src/wallet/init.cpp
+++ b/src/wallet/init.cpp
@@ -14,7 +14,7 @@
 #include <wallet/wallet.h>
 #include <wallet/walletutil.h>
 
-std::string GetWalletHelpString(bool showDebug)
+std::string WalletInit::GetHelpString(bool showDebug)
 {
     std::string strUsage = HelpMessageGroup(_("Wallet options:"));
     strUsage += HelpMessageOpt("-addresstype", strprintf("What type of addresses to use (\"legacy\", \"p2sh-segwit\", or \"bech32\", default: \"%s\")", FormatOutputType(DEFAULT_ADDRESS_TYPE)));
@@ -56,7 +56,7 @@ std::string GetWalletHelpString(bool showDebug)
     return strUsage;
 }
 
-bool WalletParameterInteraction()
+bool WalletInit::ParameterInteraction()
 {
     if (gArgs.GetBoolArg("-disablewallet", DEFAULT_DISABLE_WALLET)) {
         for (const std::string& wallet : gArgs.GetArgs("-wallet")) {
@@ -184,7 +184,7 @@ bool WalletParameterInteraction()
     return true;
 }
 
-void RegisterWalletRPC(CRPCTable &t)
+void WalletInit::RegisterRPC(CRPCTable &t)
 {
     if (gArgs.GetBoolArg("-disablewallet", DEFAULT_DISABLE_WALLET)) {
         return;
@@ -193,7 +193,7 @@ void RegisterWalletRPC(CRPCTable &t)
     RegisterWalletRPCCommands(t);
 }
 
-bool VerifyWallets()
+bool WalletInit::Verify()
 {
     if (gArgs.GetBoolArg("-disablewallet", DEFAULT_DISABLE_WALLET)) {
         return true;
@@ -268,7 +268,7 @@ bool VerifyWallets()
     return true;
 }
 
-bool OpenWallets()
+bool WalletInit::Open()
 {
     if (gArgs.GetBoolArg("-disablewallet", DEFAULT_DISABLE_WALLET)) {
         LogPrintf("Wallet disabled!\n");
@@ -286,25 +286,29 @@ bool OpenWallets()
     return true;
 }
 
-void StartWallets(CScheduler& scheduler) {
+void WalletInit::Start(CScheduler& scheduler)
+{
     for (CWalletRef pwallet : vpwallets) {
         pwallet->postInitProcess(scheduler);
     }
 }
 
-void FlushWallets() {
+void WalletInit::Flush()
+{
     for (CWalletRef pwallet : vpwallets) {
         pwallet->Flush(false);
     }
 }
 
-void StopWallets() {
+void WalletInit::Stop()
+{
     for (CWalletRef pwallet : vpwallets) {
         pwallet->Flush(true);
     }
 }
 
-void CloseWallets() {
+void WalletInit::Close()
+{
     for (CWalletRef pwallet : vpwallets) {
         delete pwallet;
     }
diff --git a/src/wallet/init.h b/src/wallet/init.h
index 0b3ee2dda2..f8be90d3e3 100644
--- a/src/wallet/init.h
+++ b/src/wallet/init.h
@@ -6,38 +6,43 @@
 #ifndef BITCOIN_WALLET_INIT_H
 #define BITCOIN_WALLET_INIT_H
 
+#include <walletinitinterface.h>
 #include <string>
 
 class CRPCTable;
 class CScheduler;
 
-//! Return the wallets help message.
-std::string GetWalletHelpString(bool showDebug);
+class WalletInit : public WalletInitInterface {
+public:
 
-//! Wallets parameter interaction
-bool WalletParameterInteraction();
+    //! Return the wallets help message.
+    std::string GetHelpString(bool showDebug) override;
 
-//! Register wallet RPCs.
-void RegisterWalletRPC(CRPCTable &tableRPC);
+    //! Wallets parameter interaction
+    bool ParameterInteraction() override;
 
-//! Responsible for reading and validating the -wallet arguments and verifying the wallet database.
-//  This function will perform salvage on the wallet if requested, as long as only one wallet is
-//  being loaded (WalletParameterInteraction forbids -salvagewallet, -zapwallettxes or -upgradewallet with multiwallet).
-bool VerifyWallets();
+    //! Register wallet RPCs.
+    void RegisterRPC(CRPCTable &tableRPC) override;
 
-//! Load wallet databases.
-bool OpenWallets();
+    //! Responsible for reading and validating the -wallet arguments and verifying the wallet database.
+    //  This function will perform salvage on the wallet if requested, as long as only one wallet is
+    //  being loaded (WalletParameterInteraction forbids -salvagewallet, -zapwallettxes or -upgradewallet with multiwallet).
+    bool Verify() override;
 
-//! Complete startup of wallets.
-void StartWallets(CScheduler& scheduler);
+    //! Load wallet databases.
+    bool Open() override;
 
-//! Flush all wallets in preparation for shutdown.
-void FlushWallets();
+    //! Complete startup of wallets.
+    void Start(CScheduler& scheduler) override;
 
-//! Stop all wallets. Wallets will be flushed first.
-void StopWallets();
+    //! Flush all wallets in preparation for shutdown.
+    void Flush() override;
 
-//! Close all wallets.
-void CloseWallets();
+    //! Stop all wallets. Wallets will be flushed first.
+    void Stop() override;
+
+    //! Close all wallets.
+    void Close() override;
+};
 
 #endif // BITCOIN_WALLET_INIT_H
diff --git a/src/walletinitinterface.h b/src/walletinitinterface.h
new file mode 100644
index 0000000000..47e4e2cce1
--- /dev/null
+++ b/src/walletinitinterface.h
@@ -0,0 +1,51 @@
+// Copyright (c) 2017 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 WALLETINITINTERFACE_H
+#define WALLETINITINTERFACE_H
+
+#include <string>
+
+class CScheduler;
+class CRPCTable;
+
+class WalletInitInterface {
+public:
+    /** Get wallet help string */
+    virtual std::string GetHelpString(bool showDebug) = 0;
+    /** Check wallet parameter interaction */
+    virtual bool ParameterInteraction() = 0;
+    /** Register wallet RPC*/
+    virtual void RegisterRPC(CRPCTable &) = 0;
+    /** Verify wallets */
+    virtual bool Verify() = 0;
+    /** Open wallets*/
+    virtual bool Open() = 0;
+    /** Start wallets*/
+    virtual void Start(CScheduler& scheduler) = 0;
+    /** Flush Wallets*/
+    virtual void Flush() = 0;
+    /** Stop Wallets*/
+    virtual void Stop() = 0;
+    /** Close wallets */
+    virtual void Close() = 0;
+
+    virtual ~WalletInitInterface() {}
+};
+
+class DummyWalletInit : public WalletInitInterface {
+public:
+
+    std::string GetHelpString(bool showDebug) override {return std::string{};}
+    bool ParameterInteraction() override {return true;}
+    void RegisterRPC(CRPCTable &) override {}
+    bool Verify() override {return true;}
+    bool Open() override {return true;}
+    void Start(CScheduler& scheduler) override {}
+    void Flush() override {}
+    void Stop() override {}
+    void Close() override {}
+};
+
+#endif // WALLETINITINTERFACE_H