Merge #10645: Use nullptr (C++11) instead of zero (0) as the null pointer constant

36d326e8b Use nullptr instead of zero (0) as the null pointer constant (practicalswift)

Pull request description:

  Use `nullptr` instead of zero (0) as the null pointer constant.

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

  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

Tree-SHA512: 5412404b40a94ea2d9fc8f81573559c4ffe559749301d486b09d41a7a736345ad602d08ac590930bb00a49692b6075520cf3d543e4da6ccd5b29fa9bcc3f15ea

16 files changed, 41 insertions, 41 deletions

diff --git a/src/bench/lockedpool.cpp b/src/bench/lockedpool.cpp
index 43a1422795..c6a05567be 100644
--- a/src/bench/lockedpool.cpp
+++ b/src/bench/lockedpool.cpp
@@ -21,14 +21,14 @@ static void BenchLockedPool(benchmark::State& state)
 
     std::vector<void*> addr;
     for (int x=0; x<ASIZE; ++x)
-        addr.push_back(0);
+        addr.push_back(nullptr);
     uint32_t s = 0x12345678;
     while (state.KeepRunning()) {
         for (int x=0; x<BITER; ++x) {
             int idx = s & (addr.size()-1);
             if (s & 0x80000000) {
                 b.free(addr[idx]);
-                addr[idx] = 0;
+                addr[idx] = nullptr;
             } else if(!addr[idx]) {
                 addr[idx] = b.alloc((s >> 16) & (MSIZE-1));
             }
diff --git a/src/coins.cpp b/src/coins.cpp
index e30bda930a..b45dfc3342 100644
--- a/src/coins.cpp
+++ b/src/coins.cpp
@@ -14,7 +14,7 @@ bool CCoinsView::GetCoin(const COutPoint &outpoint, Coin &coin) const { return f
 uint256 CCoinsView::GetBestBlock() const { return uint256(); }
 std::vector<uint256> CCoinsView::GetHeadBlocks() const { return std::vector<uint256>(); }
 bool CCoinsView::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) { return false; }
-CCoinsViewCursor *CCoinsView::Cursor() const { return 0; }
+CCoinsViewCursor *CCoinsView::Cursor() const { return nullptr; }
 
 bool CCoinsView::HaveCoin(const COutPoint &outpoint) const
 {
diff --git a/src/httprpc.cpp b/src/httprpc.cpp
index dd219c7291..8c1a74677a 100644
--- a/src/httprpc.cpp
+++ b/src/httprpc.cpp
@@ -62,7 +62,7 @@ private:
 /* Pre-base64-encoded authentication token */
 static std::string strRPCUserColonPass;
 /* Stored RPC timer interface (for unregistration) */
-static HTTPRPCTimerInterface* httpRPCTimerInterface = 0;
+static HTTPRPCTimerInterface* httpRPCTimerInterface = nullptr;
 
 static void JSONErrorReply(HTTPRequest* req, const UniValue& objError, const UniValue& id)
 {
@@ -255,6 +255,6 @@ void StopHTTPRPC()
     if (httpRPCTimerInterface) {
         RPCUnsetTimerInterface(httpRPCTimerInterface);
         delete httpRPCTimerInterface;
-        httpRPCTimerInterface = 0;
+        httpRPCTimerInterface = nullptr;
     }
 }
diff --git a/src/httpserver.cpp b/src/httpserver.cpp
index ba3b0d1a68..815d660288 100644
--- a/src/httpserver.cpp
+++ b/src/httpserver.cpp
@@ -164,13 +164,13 @@ struct HTTPPathHandler
 /** HTTP module state */
 
 //! libevent event loop
-static struct event_base* eventBase = 0;
+static struct event_base* eventBase = nullptr;
 //! HTTP server
-struct evhttp* eventHTTP = 0;
+struct evhttp* eventHTTP = nullptr;
 //! List of subnets to allow RPC connections from
 static std::vector<CSubNet> rpc_allow_subnets;
 //! Work queue for handling longer requests off the event loop thread
-static WorkQueue<HTTPClosure>* workQueue = 0;
+static WorkQueue<HTTPClosure>* workQueue = nullptr;
 //! Handlers for (sub)paths
 std::vector<HTTPPathHandler> pathHandlers;
 //! Bound listening sockets
@@ -495,11 +495,11 @@ void StopHTTPServer()
     }
     if (eventHTTP) {
         evhttp_free(eventHTTP);
-        eventHTTP = 0;
+        eventHTTP = nullptr;
     }
     if (eventBase) {
         event_base_free(eventBase);
-        eventBase = 0;
+        eventBase = nullptr;
     }
     LogPrint(BCLog::HTTP, "Stopped HTTP server\n");
 }
@@ -601,9 +601,9 @@ void HTTPRequest::WriteReply(int nStatus, const std::string& strReply)
     evbuffer_add(evb, strReply.data(), strReply.size());
     HTTPEvent* ev = new HTTPEvent(eventBase, true,
         std::bind(evhttp_send_reply, req, nStatus, (const char*)nullptr, (struct evbuffer *)nullptr));
-    ev->trigger(0);
+    ev->trigger(nullptr);
     replySent = true;
-    req = 0; // transferred back to main thread
+    req = nullptr; // transferred back to main thread
 }
 
 CService HTTPRequest::GetPeer()
diff --git a/src/net.cpp b/src/net.cpp
index 599a6128fa..1af317726a 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -1438,9 +1438,9 @@ void CConnman::WakeMessageHandler()
 void ThreadMapPort()
 {
     std::string port = strprintf("%u", GetListenPort());
-    const char * multicastif = 0;
-    const char * minissdpdpath = 0;
-    struct UPNPDev * devlist = 0;
+    const char * multicastif = nullptr;
+    const char * minissdpdpath = nullptr;
+    struct UPNPDev * devlist = nullptr;
     char lanaddr[64];
 
 #ifndef UPNPDISCOVER_SUCCESS
@@ -1510,13 +1510,13 @@ void ThreadMapPort()
         {
             r = UPNP_DeletePortMapping(urls.controlURL, data.first.servicetype, port.c_str(), "TCP", 0);
             LogPrintf("UPNP_DeletePortMapping() returned: %d\n", r);
-            freeUPNPDevlist(devlist); devlist = 0;
+            freeUPNPDevlist(devlist); devlist = nullptr;
             FreeUPNPUrls(&urls);
             throw;
         }
     } else {
         LogPrintf("No valid UPnP IGDs found\n");
-        freeUPNPDevlist(devlist); devlist = 0;
+        freeUPNPDevlist(devlist); devlist = nullptr;
         if (r != 0)
             FreeUPNPUrls(&urls);
     }
diff --git a/src/netbase.h b/src/netbase.h
index 941da31f9c..f02c5e0b05 100644
--- a/src/netbase.h
+++ b/src/netbase.h
@@ -50,8 +50,8 @@ bool Lookup(const char *pszName, CService& addr, int portDefault, bool fAllowLoo
 bool Lookup(const char *pszName, std::vector<CService>& vAddr, int portDefault, bool fAllowLookup, unsigned int nMaxSolutions);
 CService LookupNumeric(const char *pszName, int portDefault = 0);
 bool LookupSubNet(const char *pszName, CSubNet& subnet);
-bool ConnectSocket(const CService &addr, SOCKET& hSocketRet, int nTimeout, bool *outProxyConnectionFailed = 0);
-bool ConnectSocketByName(CService &addr, SOCKET& hSocketRet, const char *pszDest, int portDefault, int nTimeout, bool *outProxyConnectionFailed = 0);
+bool ConnectSocket(const CService &addr, SOCKET& hSocketRet, int nTimeout, bool *outProxyConnectionFailed = nullptr);
+bool ConnectSocketByName(CService &addr, SOCKET& hSocketRet, const char *pszDest, int portDefault, int nTimeout, bool *outProxyConnectionFailed = nullptr);
 /** Return readable error string for a network error code */
 std::string NetworkErrorString(int err);
 /** Close socket and set hSocket to INVALID_SOCKET */
diff --git a/src/support/lockedpool.h b/src/support/lockedpool.h
index f5212bc266..7641d81471 100644
--- a/src/support/lockedpool.h
+++ b/src/support/lockedpool.h
@@ -150,7 +150,7 @@ public:
      * If this callback is provided and returns false, the allocation fails (hard fail), if
      * it returns true the allocation proceeds, but it could warn.
      */
-    LockedPool(std::unique_ptr<LockedPageAllocator> allocator, LockingFailed_Callback lf_cb_in = 0);
+    LockedPool(std::unique_ptr<LockedPageAllocator> allocator, LockingFailed_Callback lf_cb_in = nullptr);
     ~LockedPool();
 
     /** Allocate size bytes from this arena.
diff --git a/src/sync.cpp b/src/sync.cpp
index b82f3770e4..9c351ea487 100644
--- a/src/sync.cpp
+++ b/src/sync.cpp
@@ -162,7 +162,7 @@ void DeleteLock(void* cs)
         return;
     }
     boost::unique_lock<boost::mutex> lock(lockdata.dd_mutex);
-    std::pair<void*, void*> item = std::make_pair(cs, (void*)0);
+    std::pair<void*, void*> item = std::make_pair(cs, nullptr);
     LockOrders::iterator it = lockdata.lockorders.lower_bound(item);
     while (it != lockdata.lockorders.end() && it->first.first == cs) {
         std::pair<void*, void*> invitem = std::make_pair(it->first.second, it->first.first);
diff --git a/src/torcontrol.cpp b/src/torcontrol.cpp
index e8bc3e5e75..6b96c24af2 100644
--- a/src/torcontrol.cpp
+++ b/src/torcontrol.cpp
@@ -121,7 +121,7 @@ private:
 };
 
 TorControlConnection::TorControlConnection(struct event_base *_base):
-    base(_base), b_conn(0)
+    base(_base), b_conn(nullptr)
 {
 }
 
@@ -227,7 +227,7 @@ bool TorControlConnection::Disconnect()
 {
     if (b_conn)
         bufferevent_free(b_conn);
-    b_conn = 0;
+    b_conn = nullptr;
     return true;
 }
 
@@ -476,7 +476,7 @@ TorController::~TorController()
 {
     if (reconnect_ev) {
         event_free(reconnect_ev);
-        reconnect_ev = 0;
+        reconnect_ev = nullptr;
     }
     if (service.IsValid()) {
         RemoveLocal(service);
@@ -770,7 +770,7 @@ void StopTorControl()
     if (gBase) {
         torControlThread.join();
         event_base_free(gBase);
-        gBase = 0;
+        gBase = nullptr;
     }
 }
 
diff --git a/src/validation.h b/src/validation.h
index edb8eab894..d0f6cdc135 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -365,7 +365,7 @@ private:
     PrecomputedTransactionData *txdata;
 
 public:
-    CScriptCheck(): amount(0), ptxTo(0), nIn(0), nFlags(0), cacheStore(false), error(SCRIPT_ERR_UNKNOWN_ERROR) {}
+    CScriptCheck(): amount(0), ptxTo(nullptr), nIn(0), nFlags(0), cacheStore(false), error(SCRIPT_ERR_UNKNOWN_ERROR) {}
     CScriptCheck(const CScript& scriptPubKeyIn, const CAmount amountIn, const CTransaction& txToIn, unsigned int nInIn, unsigned int nFlagsIn, bool cacheIn, PrecomputedTransactionData* txdataIn) :
         scriptPubKey(scriptPubKeyIn), amount(amountIn),
         ptxTo(&txToIn), nIn(nInIn), nFlags(nFlagsIn), cacheStore(cacheIn), error(SCRIPT_ERR_UNKNOWN_ERROR), txdata(txdataIn) { }
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 75f836a29d..094357639b 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -1644,10 +1644,10 @@ UniValue listtransactions(const JSONRPCRequest& request)
     for (CWallet::TxItems::const_reverse_iterator it = txOrdered.rbegin(); it != txOrdered.rend(); ++it)
     {
         CWalletTx *const pwtx = (*it).second.first;
-        if (pwtx != 0)
+        if (pwtx != nullptr)
             ListTransactions(pwallet, *pwtx, strAccount, 0, true, ret, filter);
         CAccountingEntry *const pacentry = (*it).second.second;
-        if (pacentry != 0)
+        if (pacentry != nullptr)
             AcentryToJSON(*pacentry, strAccount, ret);
 
         if ((int)ret.size() >= (nCount+nFrom)) break;
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 489952e309..f8c6f9e87b 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -739,13 +739,13 @@ DBErrors CWallet::ReorderTransactions()
     for (std::map<uint256, CWalletTx>::iterator it = mapWallet.begin(); it != mapWallet.end(); ++it)
     {
         CWalletTx* wtx = &((*it).second);
-        txByTime.insert(std::make_pair(wtx->nTimeReceived, TxPair(wtx, (CAccountingEntry*)0)));
+        txByTime.insert(std::make_pair(wtx->nTimeReceived, TxPair(wtx, nullptr)));
     }
     std::list<CAccountingEntry> acentries;
     walletdb.ListAccountCreditDebit("", acentries);
     for (CAccountingEntry& entry : acentries)
     {
-        txByTime.insert(std::make_pair(entry.nTime, TxPair((CWalletTx*)0, &entry)));
+        txByTime.insert(std::make_pair(entry.nTime, TxPair(nullptr, &entry)));
     }
 
     nOrderPosNext = 0;
@@ -754,7 +754,7 @@ DBErrors CWallet::ReorderTransactions()
     {
         CWalletTx *const pwtx = (*it).second.first;
         CAccountingEntry *const pacentry = (*it).second.second;
-        int64_t& nOrderPos = (pwtx != 0) ? pwtx->nOrderPos : pacentry->nOrderPos;
+        int64_t& nOrderPos = (pwtx != nullptr) ? pwtx->nOrderPos : pacentry->nOrderPos;
 
         if (nOrderPos == -1)
         {
@@ -939,7 +939,7 @@ bool CWallet::AddToWallet(const CWalletTx& wtxIn, bool fFlushOnClose)
     {
         wtx.nTimeReceived = GetAdjustedTime();
         wtx.nOrderPos = IncOrderPosNext(&walletdb);
-        wtxOrdered.insert(std::make_pair(wtx.nOrderPos, TxPair(&wtx, (CAccountingEntry*)0)));
+        wtxOrdered.insert(std::make_pair(wtx.nOrderPos, TxPair(&wtx, nullptr)));
         wtx.nTimeSmart = ComputeTimeSmart(wtx);
         AddToSpends(hash);
     }
@@ -1004,7 +1004,7 @@ bool CWallet::LoadToWallet(const CWalletTx& wtxIn)
     mapWallet[hash] = wtxIn;
     CWalletTx& wtx = mapWallet[hash];
     wtx.BindWallet(this);
-    wtxOrdered.insert(std::make_pair(wtx.nOrderPos, TxPair(&wtx, (CAccountingEntry*)0)));
+    wtxOrdered.insert(std::make_pair(wtx.nOrderPos, TxPair(&wtx, nullptr)));
     AddToSpends(hash);
     for (const CTxIn& txin : wtx.tx->vin) {
         if (mapWallet.count(txin.prevout.hash)) {
@@ -1794,7 +1794,7 @@ CAmount CWalletTx::GetImmatureCredit(bool fUseCache) const
 
 CAmount CWalletTx::GetAvailableCredit(bool fUseCache) const
 {
-    if (pwallet == 0)
+    if (pwallet == nullptr)
         return 0;
 
     // Must wait until coinbase is safely deep enough in the chain before valuing it
@@ -1838,7 +1838,7 @@ CAmount CWalletTx::GetImmatureWatchOnlyCredit(const bool& fUseCache) const
 
 CAmount CWalletTx::GetAvailableWatchOnlyCredit(const bool& fUseCache) const
 {
-    if (pwallet == 0)
+    if (pwallet == nullptr)
         return 0;
 
     // Must wait until coinbase is safely deep enough in the chain before valuing it
@@ -3026,7 +3026,7 @@ bool CWallet::AddAccountingEntry(const CAccountingEntry& acentry, CWalletDB *pwa
 
     laccentries.push_back(acentry);
     CAccountingEntry & entry = laccentries.back();
-    wtxOrdered.insert(std::make_pair(entry.nOrderPos, TxPair((CWalletTx*)0, &entry)));
+    wtxOrdered.insert(std::make_pair(entry.nOrderPos, TxPair(nullptr, &entry)));
 
     return true;
 }
diff --git a/src/wallet/walletdb.cpp b/src/wallet/walletdb.cpp
index 72c22d2259..cd26d87fdb 100644
--- a/src/wallet/walletdb.cpp
+++ b/src/wallet/walletdb.cpp
@@ -621,7 +621,7 @@ DBErrors CWalletDB::LoadWallet(CWallet* pwallet)
     pwallet->laccentries.clear();
     ListAccountCreditDebit("*", pwallet->laccentries);
     for (CAccountingEntry& entry : pwallet->laccentries) {
-        pwallet->wtxOrdered.insert(make_pair(entry.nOrderPos, CWallet::TxPair((CWalletTx*)0, &entry)));
+        pwallet->wtxOrdered.insert(make_pair(entry.nOrderPos, CWallet::TxPair(nullptr, &entry)));
     }
 
     return result;
diff --git a/src/zmq/zmqabstractnotifier.h b/src/zmq/zmqabstractnotifier.h
index 77cf5141e2..7828822149 100644
--- a/src/zmq/zmqabstractnotifier.h
+++ b/src/zmq/zmqabstractnotifier.h
@@ -15,7 +15,7 @@ typedef CZMQAbstractNotifier* (*CZMQNotifierFactory)();
 class CZMQAbstractNotifier
 {
 public:
-    CZMQAbstractNotifier() : psocket(0) { }
+    CZMQAbstractNotifier() : psocket(nullptr) { }
     virtual ~CZMQAbstractNotifier();
 
     template <typename T>
diff --git a/src/zmq/zmqnotificationinterface.cpp b/src/zmq/zmqnotificationinterface.cpp
index c410cc269f..9909395d84 100644
--- a/src/zmq/zmqnotificationinterface.cpp
+++ b/src/zmq/zmqnotificationinterface.cpp
@@ -120,7 +120,7 @@ void CZMQNotificationInterface::Shutdown()
         }
         zmq_ctx_destroy(pcontext);
 
-        pcontext = 0;
+        pcontext = nullptr;
     }
 }
 
diff --git a/src/zmq/zmqpublishnotifier.cpp b/src/zmq/zmqpublishnotifier.cpp
index 700c39f66e..ab54e2bb8b 100644
--- a/src/zmq/zmqpublishnotifier.cpp
+++ b/src/zmq/zmqpublishnotifier.cpp
@@ -126,7 +126,7 @@ void CZMQAbstractPublishNotifier::Shutdown()
         zmq_close(psocket);
     }
 
-    psocket = 0;
+    psocket = nullptr;
 }
 
 bool CZMQAbstractPublishNotifier::SendMessage(const char *command, const void* data, size_t size)
@@ -136,7 +136,7 @@ bool CZMQAbstractPublishNotifier::SendMessage(const char *command, const void* d
     /* send three parts, command & data & a LE 4byte sequence number */
     unsigned char msgseq[sizeof(uint32_t)];
     WriteLE32(&msgseq[0], nSequence);
-    int rc = zmq_send_multipart(psocket, command, strlen(command), data, size, msgseq, (size_t)sizeof(uint32_t), (void*)0);
+    int rc = zmq_send_multipart(psocket, command, strlen(command), data, size, msgseq, (size_t)sizeof(uint32_t), nullptr);
     if (rc == -1)
         return false;