Merge #15457: Check std::system for -[alert|block|wallet]notify

f874e14cd3c84cd412bd3fb42b3ee1706ca6a267 [build]: check std::system for -[alert|block|wallet]notify (Sjors Provoost)
cc3ad56ff2bc2583fe68c4a9e0b41072a47c0b07 [build] MSVC: set HAVE_SYSTEM for desktop apps (Sjors Provoost)
c1c91bb78d7267f01ee3a3c156c218b46a92cd39 [build] detect std::system or ::wsystem (Sjors Provoost)

Pull request description:

  Platforms such as iOs and Universal Windows Platform do not support launching a process through system().

ACKs for top commit:
  laanwj:
    code review ACK f874e14cd3c84cd412bd3fb42b3ee1706ca6a267

Tree-SHA512: 16bb4a8fa1896046ccb22a46c8985e1aa45f5b11ecf5539eb2299e9a58f1a5b085c0c12cb6939c7493d93abce7e84fadcbfc73374c887db63da6d00c08aa476d

8 files changed, 51 insertions, 0 deletions

diff --git a/build_msvc/bitcoin_config.h b/build_msvc/bitcoin_config.h
index ab13f73539..66cc1208a1 100644
--- a/build_msvc/bitcoin_config.h
+++ b/build_msvc/bitcoin_config.h
@@ -421,4 +421,14 @@
 /* Define for large files, on AIX-style hosts. */
 /* #undef _LARGE_FILES */
 
+/* Windows Universal Platform constraints */
+#if !defined(WINAPI_FAMILY) || (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP)
+/* Either a desktop application without API restrictions, or and older system
+   before these macros were defined. */
+
+/* ::wsystem is available */
+#define HAVE_SYSTEM 1
+
+#endif // !WINAPI_FAMILY || WINAPI_FAMILY_DESKTOP_APP
+
 #endif //BITCOIN_BITCOIN_CONFIG_H
diff --git a/configure.ac b/configure.ac
index 5e1a5e14a1..1d5a41ab9a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -925,6 +925,29 @@ if test x$use_reduce_exports = xyes; then
   [AC_MSG_ERROR([Cannot set default symbol visibility. Use --disable-reduce-exports.])])
 fi
 
+AC_MSG_CHECKING([for std::system])
+AC_LINK_IFELSE(
+    [ AC_LANG_PROGRAM(
+        [[ #include <cstdlib> ]],
+        [[ int nErr = std::system(""); ]]
+    )],
+    [ AC_MSG_RESULT(yes); AC_DEFINE(HAVE_STD__SYSTEM, 1, Define to 1 if you have the `std::system' function.)],
+    [ AC_MSG_RESULT(no) ]
+)
+
+AC_MSG_CHECKING([for ::_wsystem])
+AC_LINK_IFELSE(
+    [ AC_LANG_PROGRAM(
+        [[ ]],
+        [[ int nErr = ::_wsystem(""); ]]
+    )],
+    [ AC_MSG_RESULT(yes); AC_DEFINE(HAVE_WSYSTEM, 1, Define to 1 if you have the `::wsystem' function.)],
+    [ AC_MSG_RESULT(no) ]
+)
+
+# Define to 1 if std::system or ::wsystem (Windows) is available
+AC_DEFINE([HAVE_SYSTEM], [HAVE_STD__SYSTEM || HAVE_WSYSTEM], [std::system or ::wsystem])
+
 LEVELDB_CPPFLAGS=
 LIBLEVELDB=
 LIBMEMENV=
diff --git a/src/init.cpp b/src/init.cpp
index 6625080c6e..e2a1b99e37 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -376,10 +376,14 @@ void SetupServerArgs()
         "-allowselfsignedrootcertificates", "-choosedatadir", "-lang=<lang>", "-min", "-resetguisettings", "-rootcertificates=<file>", "-splash", "-uiplatform"};
 
     gArgs.AddArg("-version", "Print version and exit", false, OptionsCategory::OPTIONS);
+#if defined(HAVE_SYSTEM)
     gArgs.AddArg("-alertnotify=<cmd>", "Execute command when a relevant alert is received or we see a really long fork (%s in cmd is replaced by message)", false, OptionsCategory::OPTIONS);
+#endif
     gArgs.AddArg("-assumevalid=<hex>", strprintf("If this block is in the chain assume that it and its ancestors are valid and potentially skip their script verification (0 to verify all, default: %s, testnet: %s)", defaultChainParams->GetConsensus().defaultAssumeValid.GetHex(), testnetChainParams->GetConsensus().defaultAssumeValid.GetHex()), false, OptionsCategory::OPTIONS);
     gArgs.AddArg("-blocksdir=<dir>", "Specify directory to hold blocks subdirectory for *.dat files (default: <datadir>)", false, OptionsCategory::OPTIONS);
+#if defined(HAVE_SYSTEM)
     gArgs.AddArg("-blocknotify=<cmd>", "Execute command when the best block changes (%s in cmd is replaced by block hash)", false, OptionsCategory::OPTIONS);
+#endif
     gArgs.AddArg("-blockreconstructionextratxn=<n>", strprintf("Extra transactions to keep in memory for compact block reconstructions (default: %u)", DEFAULT_BLOCK_RECONSTRUCTION_EXTRA_TXN), false, OptionsCategory::OPTIONS);
     gArgs.AddArg("-blocksonly", strprintf("Whether to reject transactions from network peers. Transactions from the wallet or RPC are not affected. (default: %u)", DEFAULT_BLOCKSONLY), false, OptionsCategory::OPTIONS);
     gArgs.AddArg("-conf=<file>", strprintf("Specify configuration file. Relative paths will be prefixed by datadir location. (default: %s)", BITCOIN_CONF_FILENAME), false, OptionsCategory::OPTIONS);
@@ -579,6 +583,7 @@ std::string LicenseInfo()
            "\n";
 }
 
+#if defined(HAVE_SYSTEM)
 static void BlockNotifyCallback(bool initialSync, const CBlockIndex *pBlockIndex)
 {
     if (initialSync || !pBlockIndex)
@@ -591,6 +596,7 @@ static void BlockNotifyCallback(bool initialSync, const CBlockIndex *pBlockIndex
         t.detach(); // thread runs free
     }
 }
+#endif
 
 static bool fHaveGenesis = false;
 static Mutex g_genesis_wait_mutex;
@@ -1708,8 +1714,10 @@ bool AppInitMain(InitInterfaces& interfaces)
         fHaveGenesis = true;
     }
 
+#if defined(HAVE_SYSTEM)
     if (gArgs.IsArgSet("-blocknotify"))
         uiInterface.NotifyBlockTip_connect(BlockNotifyCallback);
+#endif
 
     std::vector<fs::path> vImportFiles;
     for (const std::string& strFile : gArgs.GetArgs("-loadblock")) {
diff --git a/src/util/system.cpp b/src/util/system.cpp
index 87ff6e62ba..0f599b85f1 100644
--- a/src/util/system.cpp
+++ b/src/util/system.cpp
@@ -1114,6 +1114,7 @@ fs::path GetSpecialFolderPath(int nFolder, bool fCreate)
 }
 #endif
 
+#if defined(HAVE_SYSTEM)
 void runCommand(const std::string& strCommand)
 {
     if (strCommand.empty()) return;
@@ -1125,6 +1126,7 @@ void runCommand(const std::string& strCommand)
     if (nErr)
         LogPrintf("runCommand error: system(%s) returned %d\n", strCommand, nErr);
 }
+#endif
 
 void SetupEnvironment()
 {
diff --git a/src/util/system.h b/src/util/system.h
index 15d7b1b402..fd0583658b 100644
--- a/src/util/system.h
+++ b/src/util/system.h
@@ -89,7 +89,9 @@ fs::path GetConfigFile(const std::string& confPath);
 #ifdef WIN32
 fs::path GetSpecialFolderPath(int nFolder, bool fCreate = true);
 #endif
+#if defined(HAVE_SYSTEM)
 void runCommand(const std::string& strCommand);
+#endif
 
 /**
  * Most paths passed as configuration arguments are treated as relative to
diff --git a/src/validation.cpp b/src/validation.cpp
index c6995ed24b..76bbb7920b 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1050,6 +1050,7 @@ static CBlockIndex *pindexBestForkTip = nullptr, *pindexBestForkBase = nullptr;
 static void AlertNotify(const std::string& strMessage)
 {
     uiInterface.NotifyAlertChanged();
+#if defined(HAVE_SYSTEM)
     std::string strCmd = gArgs.GetArg("-alertnotify", "");
     if (strCmd.empty()) return;
 
@@ -1063,6 +1064,7 @@ static void AlertNotify(const std::string& strMessage)
 
     std::thread t(runCommand, strCmd);
     t.detach(); // thread runs free
+#endif
 }
 
 static void CheckForkWarningConditions() EXCLUSIVE_LOCKS_REQUIRED(cs_main)
diff --git a/src/wallet/init.cpp b/src/wallet/init.cpp
index 0265433863..0085c3bac9 100644
--- a/src/wallet/init.cpp
+++ b/src/wallet/init.cpp
@@ -57,7 +57,9 @@ void WalletInit::AddWalletOptions() const
     gArgs.AddArg("-wallet=<path>", "Specify wallet database path. Can be specified multiple times to load multiple wallets. Path is interpreted relative to <walletdir> if it is not absolute, and will be created if it does not exist (as a directory containing a wallet.dat file and log files). For backwards compatibility this will also accept names of existing data files in <walletdir>.)", false, OptionsCategory::WALLET);
     gArgs.AddArg("-walletbroadcast",  strprintf("Make the wallet broadcast transactions (default: %u)", DEFAULT_WALLETBROADCAST), false, OptionsCategory::WALLET);
     gArgs.AddArg("-walletdir=<dir>", "Specify directory to hold wallets (default: <datadir>/wallets if it exists, otherwise <datadir>)", false, OptionsCategory::WALLET);
+#if defined(HAVE_SYSTEM)
     gArgs.AddArg("-walletnotify=<cmd>", "Execute command when a wallet transaction changes (%s in cmd is replaced by TxID)", false, OptionsCategory::WALLET);
+#endif
     gArgs.AddArg("-walletrbf", strprintf("Send transactions with full-RBF opt-in enabled (RPC only, default: %u)", DEFAULT_WALLET_RBF), false, OptionsCategory::WALLET);
     gArgs.AddArg("-zapwallettxes=<mode>", "Delete all wallet transactions and only recover those parts of the blockchain through -rescan on startup"
                                " (1 = keep tx meta data e.g. payment request information, 2 = drop tx meta data)", false, OptionsCategory::WALLET);
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 8807acb6b7..70fc06a7e7 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1050,6 +1050,7 @@ bool CWallet::AddToWallet(const CWalletTx& wtxIn, bool fFlushOnClose)
     // Notify UI of new or updated transaction
     NotifyTransactionChanged(this, hash, fInsertedNew ? CT_NEW : CT_UPDATED);
 
+#if defined(HAVE_SYSTEM)
     // notify an external script when a wallet transaction comes in or is updated
     std::string strCmd = gArgs.GetArg("-walletnotify", "");
 
@@ -1059,6 +1060,7 @@ bool CWallet::AddToWallet(const CWalletTx& wtxIn, bool fFlushOnClose)
         std::thread t(runCommand, strCmd);
         t.detach(); // thread runs free
     }
+#endif
 
     return true;
 }