Merge #10483: scripted-diff: Use the C++11 keyword nullptr to denote the pointer literal instead of the macro NULL

90d4d89 scripted-diff: Use the C++11 keyword nullptr to denote the pointer literal instead of the macro NULL (practicalswift)

Pull request description:

  Since C++11 the macro `NULL` may be:
  * an integer literal with value zero, or
  * a prvalue of type `std::nullptr_t`

  By using the C++11 keyword `nullptr` we are guaranteed a prvalue of type `std::nullptr_t`.

  For a more thorough discussion, see "A name for the null pointer: nullptr" (Sutter &
  Stroustrup), http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2431.pdf

  With this patch applied there are no `NULL` macro usages left in the repo:

  ```
  $ git grep NULL -- "*.cpp" "*.h" | egrep -v '(/univalue/|/secp256k1/|/leveldb/|_NULL|NULLDUMMY|torcontrol.*NULL|NULL cert)' | wc -l
  0
  ```

  The road towards `nullptr` (C++11) is split into two PRs:
  * `NULL` → `nullptr` is handled in PR #10483 (scripted, this PR)
  * `0` → `nullptr` is handled in PR #10645 (manual)

Tree-SHA512: 3c395d66f2ad724a8e6fed74b93634de8bfc0c0eafac94e64e5194c939499fefd6e68f047de3083ad0b4eff37df9a8a3a76349aa17d55eabbd8e0412f140a297

9 files changed, 75 insertions, 75 deletions

diff --git a/src/wallet/db.cpp b/src/wallet/db.cpp
index da2d180756..4c06c2c1f9 100644
--- a/src/wallet/db.cpp
+++ b/src/wallet/db.cpp
@@ -47,7 +47,7 @@ void CDBEnv::Reset()
     fMockDb = false;
 }
 
-CDBEnv::CDBEnv() : dbenv(NULL)
+CDBEnv::CDBEnv() : dbenv(nullptr)
 {
     Reset();
 }
@@ -56,7 +56,7 @@ CDBEnv::~CDBEnv()
 {
     EnvShutdown();
     delete dbenv;
-    dbenv = NULL;
+    dbenv = nullptr;
 }
 
 void CDBEnv::Close()
@@ -125,7 +125,7 @@ void CDBEnv::MakeMock()
     dbenv->set_lk_max_objects(10000);
     dbenv->set_flags(DB_AUTO_COMMIT, 1);
     dbenv->log_set_config(DB_LOG_IN_MEMORY, 1);
-    int ret = dbenv->open(NULL,
+    int ret = dbenv->open(nullptr,
                          DB_CREATE |
                              DB_INIT_LOCK |
                              DB_INIT_LOG |
@@ -147,10 +147,10 @@ CDBEnv::VerifyResult CDBEnv::Verify(const std::string& strFile, recoverFunc_type
     assert(mapFileUseCount.count(strFile) == 0);
 
     Db db(dbenv, 0);
-    int result = db.verify(strFile.c_str(), NULL, NULL, 0);
+    int result = db.verify(strFile.c_str(), nullptr, nullptr, 0);
     if (result == 0)
         return VERIFY_OK;
-    else if (recoverFunc == NULL)
+    else if (recoverFunc == nullptr)
         return RECOVER_FAIL;
 
     // Try to recover:
@@ -170,7 +170,7 @@ bool CDB::Recover(const std::string& filename, void *callbackDataIn, bool (*reco
     int64_t now = GetTime();
     newFilename = strprintf("%s.%d.bak", filename, now);
 
-    int result = bitdb.dbenv->dbrename(NULL, filename.c_str(), NULL,
+    int result = bitdb.dbenv->dbrename(nullptr, filename.c_str(), nullptr,
                                        newFilename.c_str(), DB_AUTO_COMMIT);
     if (result == 0)
         LogPrintf("Renamed %s to %s\n", filename, newFilename);
@@ -190,7 +190,7 @@ bool CDB::Recover(const std::string& filename, void *callbackDataIn, bool (*reco
     LogPrintf("Salvage(aggressive) found %u records\n", salvagedData.size());
 
     std::unique_ptr<Db> pdbCopy(new Db(bitdb.dbenv, 0));
-    int ret = pdbCopy->open(NULL,               // Txn pointer
+    int ret = pdbCopy->open(nullptr,               // Txn pointer
                             filename.c_str(),   // Filename
                             "main",             // Logical db name
                             DB_BTREE,           // Database type
@@ -299,7 +299,7 @@ bool CDBEnv::Salvage(const std::string& strFile, bool fAggressive, std::vector<C
     std::stringstream strDump;
 
     Db db(dbenv, 0);
-    int result = db.verify(strFile.c_str(), NULL, &strDump, flags);
+    int result = db.verify(strFile.c_str(), nullptr, &strDump, flags);
     if (result == DB_VERIFY_BAD) {
         LogPrintf("CDBEnv::Salvage: Database salvage found errors, all data may not be recoverable.\n");
         if (!fAggressive) {
@@ -357,7 +357,7 @@ void CDBEnv::CheckpointLSN(const std::string& strFile)
 }
 
 
-CDB::CDB(CWalletDBWrapper& dbw, const char* pszMode, bool fFlushOnCloseIn) : pdb(NULL), activeTxn(NULL)
+CDB::CDB(CWalletDBWrapper& dbw, const char* pszMode, bool fFlushOnCloseIn) : pdb(nullptr), activeTxn(nullptr)
 {
     fReadOnly = (!strchr(pszMode, '+') && !strchr(pszMode, 'w'));
     fFlushOnClose = fFlushOnCloseIn;
@@ -367,7 +367,7 @@ CDB::CDB(CWalletDBWrapper& dbw, const char* pszMode, bool fFlushOnCloseIn) : pdb
     }
     const std::string &strFilename = dbw.strFile;
 
-    bool fCreate = strchr(pszMode, 'c') != NULL;
+    bool fCreate = strchr(pszMode, 'c') != nullptr;
     unsigned int nFlags = DB_THREAD;
     if (fCreate)
         nFlags |= DB_CREATE;
@@ -380,7 +380,7 @@ CDB::CDB(CWalletDBWrapper& dbw, const char* pszMode, bool fFlushOnCloseIn) : pdb
         strFile = strFilename;
         ++env->mapFileUseCount[strFile];
         pdb = env->mapDb[strFile];
-        if (pdb == NULL) {
+        if (pdb == nullptr) {
             int ret;
             pdb = new Db(env->dbenv, 0);
 
@@ -392,8 +392,8 @@ CDB::CDB(CWalletDBWrapper& dbw, const char* pszMode, bool fFlushOnCloseIn) : pdb
                     throw std::runtime_error(strprintf("CDB: Failed to configure for no temp file backing for database %s", strFile));
             }
 
-            ret = pdb->open(NULL,                               // Txn pointer
-                            fMockDb ? NULL : strFile.c_str(),   // Filename
+            ret = pdb->open(nullptr,                               // Txn pointer
+                            fMockDb ? nullptr : strFile.c_str(),   // Filename
                             fMockDb ? strFile.c_str() : "main", // Logical db name
                             DB_BTREE,                           // Database type
                             nFlags,                             // Flags
@@ -401,7 +401,7 @@ CDB::CDB(CWalletDBWrapper& dbw, const char* pszMode, bool fFlushOnCloseIn) : pdb
 
             if (ret != 0) {
                 delete pdb;
-                pdb = NULL;
+                pdb = nullptr;
                 --env->mapFileUseCount[strFile];
                 strFile = "";
                 throw std::runtime_error(strprintf("CDB: Error %d, can't open database %s", ret, strFilename));
@@ -443,8 +443,8 @@ void CDB::Close()
         return;
     if (activeTxn)
         activeTxn->abort();
-    activeTxn = NULL;
-    pdb = NULL;
+    activeTxn = nullptr;
+    pdb = nullptr;
 
     if (fFlushOnClose)
         Flush();
@@ -459,12 +459,12 @@ void CDBEnv::CloseDb(const std::string& strFile)
 {
     {
         LOCK(cs_db);
-        if (mapDb[strFile] != NULL) {
+        if (mapDb[strFile] != nullptr) {
             // Close the database handle
             Db* pdb = mapDb[strFile];
             pdb->close(0);
             delete pdb;
-            mapDb[strFile] = NULL;
+            mapDb[strFile] = nullptr;
         }
     }
 }
@@ -492,7 +492,7 @@ bool CDB::Rewrite(CWalletDBWrapper& dbw, const char* pszSkip)
                     CDB db(dbw, "r");
                     Db* pdbCopy = new Db(env->dbenv, 0);
 
-                    int ret = pdbCopy->open(NULL,               // Txn pointer
+                    int ret = pdbCopy->open(nullptr,               // Txn pointer
                                             strFileRes.c_str(), // Filename
                                             "main",             // Logical db name
                                             DB_BTREE,           // Database type
@@ -527,7 +527,7 @@ bool CDB::Rewrite(CWalletDBWrapper& dbw, const char* pszSkip)
                             }
                             Dbt datKey(ssKey.data(), ssKey.size());
                             Dbt datValue(ssValue.data(), ssValue.size());
-                            int ret2 = pdbCopy->put(NULL, &datKey, &datValue, DB_NOOVERWRITE);
+                            int ret2 = pdbCopy->put(nullptr, &datKey, &datValue, DB_NOOVERWRITE);
                             if (ret2 > 0)
                                 fSuccess = false;
                         }
@@ -541,10 +541,10 @@ bool CDB::Rewrite(CWalletDBWrapper& dbw, const char* pszSkip)
                 }
                 if (fSuccess) {
                     Db dbA(env->dbenv, 0);
-                    if (dbA.remove(strFile.c_str(), NULL, 0))
+                    if (dbA.remove(strFile.c_str(), nullptr, 0))
                         fSuccess = false;
                     Db dbB(env->dbenv, 0);
-                    if (dbB.rename(strFileRes.c_str(), NULL, strFile.c_str(), 0))
+                    if (dbB.rename(strFileRes.c_str(), nullptr, strFile.c_str(), 0))
                         fSuccess = false;
                 }
                 if (!fSuccess)
diff --git a/src/wallet/db.h b/src/wallet/db.h
index 4f3ad0c42d..3614e34fbb 100644
--- a/src/wallet/db.h
+++ b/src/wallet/db.h
@@ -77,10 +77,10 @@ public:
 
     DbTxn* TxnBegin(int flags = DB_TXN_WRITE_NOSYNC)
     {
-        DbTxn* ptxn = NULL;
-        int ret = dbenv->txn_begin(NULL, &ptxn, flags);
+        DbTxn* ptxn = nullptr;
+        int ret = dbenv->txn_begin(nullptr, &ptxn, flags);
         if (!ptxn || ret != 0)
-            return NULL;
+            return nullptr;
         return ptxn;
     }
 };
@@ -191,7 +191,7 @@ public:
         int ret = pdb->get(activeTxn, &datKey, &datValue, 0);
         memory_cleanse(datKey.get_data(), datKey.get_size());
         bool success = false;
-        if (datValue.get_data() != NULL) {
+        if (datValue.get_data() != nullptr) {
             // Unserialize value
             try {
                 CDataStream ssValue((char*)datValue.get_data(), (char*)datValue.get_data() + datValue.get_size(), SER_DISK, CLIENT_VERSION);
@@ -282,11 +282,11 @@ public:
     Dbc* GetCursor()
     {
         if (!pdb)
-            return NULL;
-        Dbc* pcursor = NULL;
-        int ret = pdb->cursor(NULL, &pcursor, 0);
+            return nullptr;
+        Dbc* pcursor = nullptr;
+        int ret = pdb->cursor(nullptr, &pcursor, 0);
         if (ret != 0)
-            return NULL;
+            return nullptr;
         return pcursor;
     }
 
@@ -306,7 +306,7 @@ public:
         int ret = pcursor->get(&datKey, &datValue, fFlags);
         if (ret != 0)
             return ret;
-        else if (datKey.get_data() == NULL || datValue.get_data() == NULL)
+        else if (datKey.get_data() == nullptr || datValue.get_data() == nullptr)
             return 99999;
 
         // Convert to streams
@@ -342,7 +342,7 @@ public:
         if (!pdb || !activeTxn)
             return false;
         int ret = activeTxn->commit(0);
-        activeTxn = NULL;
+        activeTxn = nullptr;
         return (ret == 0);
     }
 
@@ -351,7 +351,7 @@ public:
         if (!pdb || !activeTxn)
             return false;
         int ret = activeTxn->abort();
-        activeTxn = NULL;
+        activeTxn = nullptr;
         return (ret == 0);
     }
 
@@ -366,7 +366,7 @@ public:
         return Write(std::string("version"), nVersion);
     }
 
-    bool static Rewrite(CWalletDBWrapper& dbw, const char* pszSkip = NULL);
+    bool static Rewrite(CWalletDBWrapper& dbw, const char* pszSkip = nullptr);
 };
 
 #endif // BITCOIN_WALLET_DB_H
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 057379d8da..8ef33f248b 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -1818,8 +1818,8 @@ UniValue listsinceblock(const JSONRPCRequest& request)
 
     LOCK2(cs_main, pwallet->cs_wallet);
 
-    const CBlockIndex* pindex = NULL;    // Block index of the specified block or the common ancestor, if the block provided was in a deactivated chain.
-    const CBlockIndex* paltindex = NULL; // Block index of the specified block, even if it's in a deactivated chain.
+    const CBlockIndex* pindex = nullptr;    // Block index of the specified block or the common ancestor, if the block provided was in a deactivated chain.
+    const CBlockIndex* paltindex = nullptr; // Block index of the specified block, even if it's in a deactivated chain.
     int target_confirms = 1;
     isminefilter filter = ISMINE_SPENDABLE;
 
@@ -2725,10 +2725,10 @@ UniValue listunspent(const JSONRPCRequest& request)
 
     UniValue results(UniValue::VARR);
     std::vector<COutput> vecOutputs;
-    assert(pwallet != NULL);
+    assert(pwallet != nullptr);
     LOCK2(cs_main, pwallet->cs_wallet);
 
-    pwallet->AvailableCoins(vecOutputs, !include_unsafe, NULL, nMinimumAmount, nMaximumAmount, nMinimumSumAmount, nMaximumCount, nMinDepth, nMaxDepth);
+    pwallet->AvailableCoins(vecOutputs, !include_unsafe, nullptr, nMinimumAmount, nMaximumAmount, nMinimumSumAmount, nMaximumCount, nMinDepth, nMaxDepth);
     for (const COutput& out : vecOutputs) {
         CTxDestination address;
         const CScript& scriptPubKey = out.tx->tx->vout[out.i].scriptPubKey;
diff --git a/src/wallet/rpcwallet.h b/src/wallet/rpcwallet.h
index 31e2f6a699..db0808b93b 100644
--- a/src/wallet/rpcwallet.h
+++ b/src/wallet/rpcwallet.h
@@ -14,7 +14,7 @@ void RegisterWalletRPCCommands(CRPCTable &t);
  * Figures out what wallet, if any, to use for a JSONRPCRequest.
  *
  * @param[in] request JSONRPCRequest that wishes to access a wallet
- * @return NULL if no wallet should be used, or a pointer to the CWallet
+ * @return nullptr if no wallet should be used, or a pointer to the CWallet
  */
 CWallet *GetWalletForJSONRPCRequest(const JSONRPCRequest& request);
 
diff --git a/src/wallet/test/crypto_tests.cpp b/src/wallet/test/crypto_tests.cpp
index 744063624c..98d957b322 100644
--- a/src/wallet/test/crypto_tests.cpp
+++ b/src/wallet/test/crypto_tests.cpp
@@ -48,7 +48,7 @@ bool OldEncrypt(const CKeyingMaterial& vchPlaintext, std::vector<unsigned char>
     bool fOk = true;
 
     EVP_CIPHER_CTX_init(ctx);
-    if (fOk) fOk = EVP_EncryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, chKey, chIV) != 0;
+    if (fOk) fOk = EVP_EncryptInit_ex(ctx, EVP_aes_256_cbc(), nullptr, chKey, chIV) != 0;
     if (fOk) fOk = EVP_EncryptUpdate(ctx, &vchCiphertext[0], &nCLen, &vchPlaintext[0], nLen) != 0;
     if (fOk) fOk = EVP_EncryptFinal_ex(ctx, (&vchCiphertext[0]) + nCLen, &nFLen) != 0;
     EVP_CIPHER_CTX_cleanup(ctx);
@@ -76,7 +76,7 @@ bool OldDecrypt(const std::vector<unsigned char>& vchCiphertext, CKeyingMaterial
     bool fOk = true;
 
     EVP_CIPHER_CTX_init(ctx);
-    if (fOk) fOk = EVP_DecryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, chKey, chIV) != 0;
+    if (fOk) fOk = EVP_DecryptInit_ex(ctx, EVP_aes_256_cbc(), nullptr, chKey, chIV) != 0;
     if (fOk) fOk = EVP_DecryptUpdate(ctx, &vchPlaintext[0], &nPLen, &vchCiphertext[0], nLen) != 0;
     if (fOk) fOk = EVP_DecryptFinal_ex(ctx, (&vchPlaintext[0]) + nPLen, &nFLen) != 0;
     EVP_CIPHER_CTX_cleanup(ctx);
diff --git a/src/wallet/test/wallet_test_fixture.cpp b/src/wallet/test/wallet_test_fixture.cpp
index 922fcc8e89..e2f48c45ab 100644
--- a/src/wallet/test/wallet_test_fixture.cpp
+++ b/src/wallet/test/wallet_test_fixture.cpp
@@ -28,7 +28,7 @@ WalletTestingSetup::~WalletTestingSetup()
 {
     UnregisterValidationInterface(pwalletMain);
     delete pwalletMain;
-    pwalletMain = NULL;
+    pwalletMain = nullptr;
 
     bitdb.Flush(true);
     bitdb.Reset();
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 8b03421691..c152b9d697 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -118,7 +118,7 @@ const CWalletTx* CWallet::GetWalletTx(const uint256& hash) const
     LOCK(cs_wallet);
     std::map<uint256, CWalletTx>::const_iterator it = mapWallet.find(hash);
     if (it == mapWallet.end())
-        return NULL;
+        return nullptr;
     return &(it->second);
 }
 
@@ -215,10 +215,10 @@ bool CWallet::AddKeyPubKeyWithDB(CWalletDB &walletdb, const CKey& secret, const
         pwalletdbEncryption = &walletdb;
     }
     if (!CCryptoKeyStore::AddKeyPubKey(secret, pubkey)) {
-        if (needsDB) pwalletdbEncryption = NULL;
+        if (needsDB) pwalletdbEncryption = nullptr;
         return false;
     }
-    if (needsDB) pwalletdbEncryption = NULL;
+    if (needsDB) pwalletdbEncryption = nullptr;
 
     // check if we need to remove from watch-only
     CScript script;
@@ -558,7 +558,7 @@ void CWallet::SyncMetaData(std::pair<TxSpends::iterator, TxSpends::iterator> ran
     // So: find smallest nOrderPos:
 
     int nMinOrderPos = std::numeric_limits<int>::max();
-    const CWalletTx* copyFrom = NULL;
+    const CWalletTx* copyFrom = nullptr;
     for (TxSpends::iterator it = range.first; it != range.second; ++it)
     {
         const uint256& hash = it->second;
@@ -673,7 +673,7 @@ bool CWallet::EncryptWallet(const SecureString& strWalletPassphrase)
         pwalletdbEncryption = new CWalletDB(*dbw);
         if (!pwalletdbEncryption->TxnBegin()) {
             delete pwalletdbEncryption;
-            pwalletdbEncryption = NULL;
+            pwalletdbEncryption = nullptr;
             return false;
         }
         pwalletdbEncryption->WriteMasterKey(nMasterKeyMaxID, kMasterKey);
@@ -698,7 +698,7 @@ bool CWallet::EncryptWallet(const SecureString& strWalletPassphrase)
         }
 
         delete pwalletdbEncryption;
-        pwalletdbEncryption = NULL;
+        pwalletdbEncryption = nullptr;
 
         Lock();
         Unlock(strWalletPassphrase);
@@ -1021,7 +1021,7 @@ bool CWallet::LoadToWallet(const CWalletTx& wtxIn)
 /**
  * Add a transaction to the wallet, or update it.  pIndex and posInBlock should
  * be set when the transaction was known to be included in a block.  When
- * pIndex == NULL, then wallet state is not updated in AddToWallet, but
+ * pIndex == nullptr, then wallet state is not updated in AddToWallet, but
  * notifications happen and cached balances are marked dirty.
  *
  * If fUpdate is true, existing transactions will be updated.
@@ -1037,7 +1037,7 @@ bool CWallet::AddToWalletIfInvolvingMe(const CTransactionRef& ptx, const CBlockI
     {
         AssertLockHeld(cs_wallet);
 
-        if (pIndex != NULL) {
+        if (pIndex != nullptr) {
             for (const CTxIn& txin : tx.vin) {
                 std::pair<TxSpends::const_iterator, TxSpends::const_iterator> range = mapTxSpends.equal_range(txin.prevout);
                 while (range.first != range.second) {
@@ -1081,7 +1081,7 @@ bool CWallet::AddToWalletIfInvolvingMe(const CTransactionRef& ptx, const CBlockI
             CWalletTx wtx(this, ptx);
 
             // Get merkle branch if transaction was found in a block
-            if (pIndex != NULL)
+            if (pIndex != nullptr)
                 wtx.SetMerkleBranch(pIndex, posInBlock);
 
             return AddToWallet(wtx, false);
@@ -1705,7 +1705,7 @@ bool CWalletTx::RelayWalletTransaction(CConnman* connman)
 std::set<uint256> CWalletTx::GetConflicts() const
 {
     std::set<uint256> result;
-    if (pwallet != NULL)
+    if (pwallet != nullptr)
     {
         uint256 myHash = GetHash();
         result = pwallet->GetConflicts(myHash);
@@ -1902,7 +1902,7 @@ bool CWalletTx::IsTrusted() const
     {
         // Transactions not sent by us: not trusted
         const CWalletTx* parent = pwallet->GetWalletTx(txin.prevout.hash);
-        if (parent == NULL)
+        if (parent == nullptr)
             return false;
         const CTxOut& parentOut = parent->tx->vout[txin.prevout.n];
         if (pwallet->IsMine(parentOut) != ISMINE_SPENDABLE)
@@ -3941,11 +3941,11 @@ CWallet* CWallet::CreateWalletFromFile(const std::string walletFile)
         DBErrors nZapWalletRet = tempWallet->ZapWalletTx(vWtx);
         if (nZapWalletRet != DB_LOAD_OK) {
             InitError(strprintf(_("Error loading %s: Wallet corrupted"), walletFile));
-            return NULL;
+            return nullptr;
         }
 
         delete tempWallet;
-        tempWallet = NULL;
+        tempWallet = nullptr;
     }
 
     uiInterface.InitMessage(_("Loading wallet..."));
@@ -3959,7 +3959,7 @@ CWallet* CWallet::CreateWalletFromFile(const std::string walletFile)
     {
         if (nLoadWalletRet == DB_CORRUPT) {
             InitError(strprintf(_("Error loading %s: Wallet corrupted"), walletFile));
-            return NULL;
+            return nullptr;
         }
         else if (nLoadWalletRet == DB_NONCRITICAL_ERROR)
         {
@@ -3969,16 +3969,16 @@ CWallet* CWallet::CreateWalletFromFile(const std::string walletFile)
         }
         else if (nLoadWalletRet == DB_TOO_NEW) {
             InitError(strprintf(_("Error loading %s: Wallet requires newer version of %s"), walletFile, _(PACKAGE_NAME)));
-            return NULL;
+            return nullptr;
         }
         else if (nLoadWalletRet == DB_NEED_REWRITE)
         {
             InitError(strprintf(_("Wallet needed to be rewritten: restart %s to complete"), _(PACKAGE_NAME)));
-            return NULL;
+            return nullptr;
         }
         else {
             InitError(strprintf(_("Error loading %s"), walletFile));
-            return NULL;
+            return nullptr;
         }
     }
 
@@ -3996,7 +3996,7 @@ CWallet* CWallet::CreateWalletFromFile(const std::string walletFile)
         if (nMaxVersion < walletInstance->GetVersion())
         {
             InitError(_("Cannot downgrade wallet"));
-            return NULL;
+            return nullptr;
         }
         walletInstance->SetMaxVersion(nMaxVersion);
     }
@@ -4019,7 +4019,7 @@ CWallet* CWallet::CreateWalletFromFile(const std::string walletFile)
             walletInstance->SetDefaultKey(newDefaultKey);
             if (!walletInstance->SetAddressBook(walletInstance->vchDefaultKey.GetID(), "", "receive")) {
                 InitError(_("Cannot write default address") += "\n");
-                return NULL;
+                return nullptr;
             }
         }
 
@@ -4029,11 +4029,11 @@ CWallet* CWallet::CreateWalletFromFile(const std::string walletFile)
         bool useHD = GetBoolArg("-usehd", DEFAULT_USE_HD_WALLET);
         if (walletInstance->IsHDEnabled() && !useHD) {
             InitError(strprintf(_("Error loading %s: You can't disable HD on an already existing HD wallet"), walletFile));
-            return NULL;
+            return nullptr;
         }
         if (!walletInstance->IsHDEnabled() && useHD) {
             InitError(strprintf(_("Error loading %s: You can't enable HD on an already existing non-HD wallet"), walletFile));
-            return NULL;
+            return nullptr;
         }
     }
 
@@ -4065,7 +4065,7 @@ CWallet* CWallet::CreateWalletFromFile(const std::string walletFile)
 
             if (pindexRescan != block) {
                 InitError(_("Prune: last wallet synchronisation goes beyond pruned data. You need to -reindex (download the whole blockchain again in case of pruned node)"));
-                return NULL;
+                return nullptr;
             }
         }
 
@@ -4335,5 +4335,5 @@ int CMerkleTx::GetBlocksToMaturity() const
 
 bool CMerkleTx::AcceptToMemoryPool(const CAmount& nAbsurdFee, CValidationState& state)
 {
-    return ::AcceptToMemoryPool(mempool, state, tx, true, NULL, NULL, false, nAbsurdFee);
+    return ::AcceptToMemoryPool(mempool, state, tx, true, nullptr, nullptr, false, nAbsurdFee);
 }
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 0e26d6cc6a..f97a99d82a 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -342,7 +342,7 @@ public:
 
     CWalletTx()
     {
-        Init(NULL);
+        Init(nullptr);
     }
 
     CWalletTx(const CWallet* pwalletIn, CTransactionRef arg) : CMerkleTx(std::move(arg))
@@ -386,7 +386,7 @@ public:
     template <typename Stream, typename Operation>
     inline void SerializationOp(Stream& s, Operation ser_action) {
         if (ser_action.ForRead())
-            Init(NULL);
+            Init(nullptr);
         char fSpent = false;
 
         if (!ser_action.ForRead())
@@ -663,7 +663,7 @@ private:
      * all coins from coinControl are selected; Never select unconfirmed coins
      * if they are not ours
      */
-    bool SelectCoins(const std::vector<COutput>& vAvailableCoins, const CAmount& nTargetValue, std::set<CInputCoin>& setCoinsRet, CAmount& nValueRet, const CCoinControl *coinControl = NULL) const;
+    bool SelectCoins(const std::vector<COutput>& vAvailableCoins, const CAmount& nTargetValue, std::set<CInputCoin>& setCoinsRet, CAmount& nValueRet, const CCoinControl *coinControl = nullptr) const;
 
     CWalletDB *pwalletdbEncryption;
 
@@ -694,7 +694,7 @@ private:
 
     /* Used by TransactionAddedToMemorypool/BlockConnected/Disconnected.
      * Should be called with pindexBlock and posInBlock if this is for a transaction that is included in a block. */
-    void SyncTransaction(const CTransactionRef& tx, const CBlockIndex *pindex = NULL, int posInBlock = 0);
+    void SyncTransaction(const CTransactionRef& tx, const CBlockIndex *pindex = nullptr, int posInBlock = 0);
 
     /* the HD chain data model (external chain counters) */
     CHDChain hdChain;
@@ -773,7 +773,7 @@ public:
     ~CWallet()
     {
         delete pwalletdbEncryption;
-        pwalletdbEncryption = NULL;
+        pwalletdbEncryption = nullptr;
     }
 
     void SetNull()
@@ -781,7 +781,7 @@ public:
         nWalletVersion = FEATURE_BASE;
         nWalletMaxVersion = FEATURE_BASE;
         nMasterKeyMaxID = 0;
-        pwalletdbEncryption = NULL;
+        pwalletdbEncryption = nullptr;
         nOrderPosNext = 0;
         nAccountingEntryNumber = 0;
         nNextResend = 0;
@@ -819,7 +819,7 @@ public:
     /**
      * populate vCoins with vector of available COutputs.
      */
-    void AvailableCoins(std::vector<COutput>& vCoins, bool fOnlySafe=true, const CCoinControl *coinControl = NULL, const CAmount& nMinimumAmount = 1, const CAmount& nMaximumAmount = MAX_MONEY, const CAmount& nMinimumSumAmount = MAX_MONEY, const uint64_t& nMaximumCount = 0, const int& nMinDepth = 0, const int& nMaxDepth = 9999999) const;
+    void AvailableCoins(std::vector<COutput>& vCoins, bool fOnlySafe=true, const CCoinControl *coinControl = nullptr, const CAmount& nMinimumAmount = 1, const CAmount& nMaximumAmount = MAX_MONEY, const CAmount& nMinimumSumAmount = MAX_MONEY, const uint64_t& nMaximumCount = 0, const int& nMinDepth = 0, const int& nMaxDepth = 9999999) const;
 
     /**
      * Return list of available coins and locked coins grouped by non-change output address.
@@ -908,7 +908,7 @@ public:
      * Increment the next transaction order id
      * @return next transaction order id
      */
-    int64_t IncOrderPosNext(CWalletDB *pwalletdb = NULL);
+    int64_t IncOrderPosNext(CWalletDB *pwalletdb = nullptr);
     DBErrors ReorderTransactions();
     bool AccountMove(std::string strFrom, std::string strTo, CAmount nAmount, std::string strComment = "");
     bool GetAccountPubkey(CPubKey &pubKey, std::string strAccount, bool bForceNew = false);
@@ -1043,7 +1043,7 @@ public:
     bool SetDefaultKey(const CPubKey &vchPubKey);
 
     //! signify that a particular wallet feature is now used. this may change nWalletVersion and nWalletMaxVersion if those are lower
-    bool SetMinVersion(enum WalletFeature, CWalletDB* pwalletdbIn = NULL, bool fExplicit = false);
+    bool SetMinVersion(enum WalletFeature, CWalletDB* pwalletdbIn = nullptr, bool fExplicit = false);
 
     //! change which version we're allowed to upgrade to (note that this does not immediately imply upgrading to that format)
     bool SetMaxVersion(int nVersion);
diff --git a/src/wallet/walletdb.cpp b/src/wallet/walletdb.cpp
index 65a28af46d..c8dc526264 100644
--- a/src/wallet/walletdb.cpp
+++ b/src/wallet/walletdb.cpp
@@ -787,7 +787,7 @@ bool CWalletDB::Recover(const std::string& filename, std::string& out_backup_fil
 {
     // recover without a key filter callback
     // results in recovering all record types
-    return CWalletDB::Recover(filename, NULL, NULL, out_backup_filename);
+    return CWalletDB::Recover(filename, nullptr, nullptr, out_backup_filename);
 }
 
 bool CWalletDB::RecoverKeysOnlyFilter(void *callbackData, CDataStream ssKey, CDataStream ssValue)