Don't use zero as null pointer constant (-Wzero-as-null-pointer-constant)

src/mapport.cpp

@@ -193,7 +193,7 @@ static bool ProcessUpnp()
         std::string strDesc = PACKAGE_NAME " " + FormatFullVersion();
 
         do {
-            r = UPNP_AddPortMapping(urls.controlURL, data.first.servicetype, port.c_str(), port.c_str(), lanaddr, strDesc.c_str(), "TCP", 0, "0");
+            r = UPNP_AddPortMapping(urls.controlURL, data.first.servicetype, port.c_str(), port.c_str(), lanaddr, strDesc.c_str(), "TCP", nullptr, "0");
 
             if (r != UPNPCOMMAND_SUCCESS) {
                 ret = false;
@@ -206,7 +206,7 @@ static bool ProcessUpnp()
         } while (g_mapport_interrupt.sleep_for(PORT_MAPPING_REANNOUNCE_PERIOD));
         g_mapport_interrupt.reset();
 
-        r = UPNP_DeletePortMapping(urls.controlURL, data.first.servicetype, port.c_str(), "TCP", 0);
+        r = UPNP_DeletePortMapping(urls.controlURL, data.first.servicetype, port.c_str(), "TCP", nullptr);
         LogPrintf("UPNP_DeletePortMapping() returned: %d\n", r);
         freeUPNPDevlist(devlist); devlist = nullptr;
         FreeUPNPUrls(&urls);

src/netbase.cpp

@@ -675,7 +675,7 @@ bool ConnectThroughProxy(const Proxy& proxy, const std::string& strDest, uint16_
             return false;
         }
     } else {
-        if (!Socks5(strDest, port, 0, sock)) {
+        if (!Socks5(strDest, port, nullptr, sock)) {
             return false;
         }
     }

src/qt/intro.cpp

@@ -226,7 +226,7 @@ bool Intro::showIfNeeded(bool& did_show_intro, int64_t& prune_MiB)
         }
 
         /* If current default data directory does not exist, let the user choose one */
-        Intro intro(0, Params().AssumedBlockchainSize(), Params().AssumedChainStateSize());
+        Intro intro(nullptr, Params().AssumedBlockchainSize(), Params().AssumedChainStateSize());
         intro.setDataDirectory(dataDir);
         intro.setWindowIcon(QIcon(":icons/bitcoin"));
         did_show_intro = true;

src/randomenv.cpp

@@ -363,10 +363,10 @@ void RandAddStaticEnv(CSHA512& hasher)
 
 #if HAVE_DECL_GETIFADDRS && HAVE_DECL_FREEIFADDRS
     // Network interfaces
-    struct ifaddrs *ifad = NULL;
+    struct ifaddrs *ifad = nullptr;
     getifaddrs(&ifad);
     struct ifaddrs *ifit = ifad;
-    while (ifit != NULL) {
+    while (ifit != nullptr) {
         hasher.Write((const unsigned char*)&ifit, sizeof(ifit));
         hasher.Write((const unsigned char*)ifit->ifa_name, strlen(ifit->ifa_name) + 1);
         hasher.Write((const unsigned char*)&ifit->ifa_flags, sizeof(ifit->ifa_flags));

src/support/allocators/secure.h

@@ -37,7 +37,7 @@ struct secure_allocator : public std::allocator<T> {
         typedef secure_allocator<_Other> other;
     };
 
-    T* allocate(std::size_t n, const void* hint = 0)
+    T* allocate(std::size_t n, const void* hint = nullptr)
     {
         T* allocation = static_cast<T*>(LockedPoolManager::Instance().alloc(sizeof(T) * n));
         if (!allocation) {

src/test/fuzz/crypto_diff_fuzz_chacha20.cpp

@@ -128,7 +128,7 @@ void ECRYPT_encrypt_bytes(ECRYPT_ctx* x, const u8* m, u8* c, u32 bytes)
 {
     u32 x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15;
     u32 j0, j1, j2, j3, j4, j5, j6, j7, j8, j9, j10, j11, j12, j13, j14, j15;
-    u8* ctarget = NULL;
+    u8* ctarget = nullptr;
     u8 tmp[64];
     uint32_t i;
 

src/torcontrol.cpp

@@ -306,7 +306,7 @@ std::map<std::string,std::string> ParseTorReplyMapping(const std::string &s)
 
 TorController::TorController(struct event_base* _base, const std::string& tor_control_center, const CService& target):
     base(_base),
-    m_tor_control_center(tor_control_center), conn(base), reconnect(true), reconnect_ev(0),
+    m_tor_control_center(tor_control_center), conn(base), reconnect(true), reconnect_ev(nullptr),
     reconnect_timeout(RECONNECT_TIMEOUT_START),
     m_target(target)
 {

src/wallet/wallet.cpp

@@ -2768,7 +2768,7 @@ std::shared_ptr<CWallet> CWallet::Create(WalletContext& context, const std::stri
     } else if (wallet_creation_flags & WALLET_FLAG_DISABLE_PRIVATE_KEYS) {
         // Make it impossible to disable private keys after creation
         error = strprintf(_("Error loading %s: Private keys can only be disabled during creation"), walletFile);
-        return NULL;
+        return nullptr;
     } else if (walletInstance->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
         for (auto spk_man : walletInstance->GetActiveScriptPubKeyMans()) {
             if (spk_man->HavePrivateKeys()) {