Codechange: use thread safe time functions

Functions like localtime, gmtime and asctime are not thread safe as they (might) reuse the same buffer. So use the safer _s/_r variant for localtime and gmtime, and use strftime in favour of asctime.

src/CMakeLists.txt

@@ -467,6 +467,7 @@ add_files(
     viewport_type.h
     void_cmd.cpp
     void_map.h
+    walltime_func.h
     water.h
     water_cmd.cpp
     water_map.h

src/console_cmds.cpp

@@ -41,7 +41,7 @@
 #include "rail.h"
 #include "game/game.hpp"
 #include "table/strings.h"
-#include <time.h>
+#include "walltime_func.h"
 
 #include "safeguards.h"
 
@@ -1369,10 +1369,9 @@ DEF_CONSOLE_CMD(ConGetSysDate)
 		return true;
 	}
 
-	time_t t;
-	time(&t);
-	auto timeinfo = localtime(&t);
-	IConsolePrintF(CC_DEFAULT, "System Date: %04d-%02d-%02d %02d:%02d:%02d", timeinfo->tm_year + 1900, timeinfo->tm_mon + 1, timeinfo->tm_mday, timeinfo->tm_hour, timeinfo->tm_min, timeinfo->tm_sec);
+	char buffer[lengthof("2000-01-02 03:04:05")];
+	LocalTime::Format(buffer, lastof(buffer), "%Y-%m-%d %H:%M:%S");
+	IConsolePrintF(CC_DEFAULT, "System Date: %s", buffer);
 	return true;
 }
 

src/crashlog.cpp

@@ -32,8 +32,7 @@
 #include "game/game_info.hpp"
 #include "company_base.h"
 #include "company_func.h"
-
-#include <time.h>
+#include "walltime_func.h"
 
 #ifdef WITH_ALLEGRO
 #	include <allegro.h>
@@ -333,9 +332,8 @@ char *CrashLog::LogRecentNews(char *buffer, const char *last) const
  */
 char *CrashLog::FillCrashLog(char *buffer, const char *last) const
 {
-	time_t cur_time = time(nullptr);
 	buffer += seprintf(buffer, last, "*** OpenTTD Crash Report ***\n\n");
-	buffer += seprintf(buffer, last, "Crash at: %s", asctime(gmtime(&cur_time)));
+	buffer += UTCTime::Format(buffer, last, "Crash at: %Y-%m-%d %H:%M:%S (UTC)\n");
 
 	YearMonthDay ymd;
 	ConvertDateToYMD(_date, &ymd);

src/debug.cpp

@@ -19,7 +19,7 @@
 #include "os/windows/win32.h"
 #endif
 
-#include <time.h>
+#include "walltime_func.h"
 
 #include "network/network_admin.h"
 SOCKET _debug_socket = INVALID_SOCKET;
@@ -248,8 +248,7 @@ const char *GetLogPrefix()
 {
 	static char _log_prefix[24];
 	if (_settings_client.gui.show_date_in_logs) {
-		time_t cur_time = time(nullptr);
-		strftime(_log_prefix, sizeof(_log_prefix), "[%Y-%m-%d %H:%M:%S] ", localtime(&cur_time));
+		LocalTime::Format(_log_prefix, lastof(_log_prefix), "[%Y-%m-%d %H:%M:%S] ");
 	} else {
 		*_log_prefix = '\0';
 	}

src/newgrf_profiling.cpp

@@ -13,9 +13,9 @@
 #include "string_func.h"
 #include "console_func.h"
 #include "spritecache.h"
+#include "walltime_func.h"
 
 #include <chrono>
-#include <time.h>
 
 
 std::vector<NewGRFProfiler> _newgrf_profilers;
@@ -130,10 +130,8 @@ void NewGRFProfiler::Abort()
  */
 std::string NewGRFProfiler::GetOutputFilename() const
 {
-	time_t write_time = time(nullptr);
-
 	char timestamp[16] = {};
-	strftime(timestamp, lengthof(timestamp), "%Y%m%d-%H%M", localtime(&write_time));
+	LocalTime::Format(timestamp, lastof(timestamp), "%Y%m%d-%H%M");
 
 	char filepath[MAX_PATH] = {};
 	seprintf(filepath, lastof(filepath), "%sgrfprofile-%s-%08X.csv", FiosGetScreenshotDir(), timestamp, BSWAP32(this->grffile->grfid));

src/stdafx.h

@@ -129,6 +129,7 @@
 	/* Warn about functions using 'printf' format syntax. First argument determines which parameter
 	 * is the format string, second argument is start of values passed to printf. */
 #	define WARN_FORMAT(string, args) __attribute__ ((format (printf, string, args)))
+#	define WARN_TIME_FORMAT(string) __attribute__ ((format (strftime, string, 0)))
 #	if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 7)
 #		define FINAL final
 #	else
@@ -157,6 +158,7 @@
 #	define NORETURN
 #	define CDECL
 #	define WARN_FORMAT(string, args)
+#	define WARN_TIME_FORMAT(string)
 #	define FINAL
 #	define FALLTHROUGH
 #	include <malloc.h>
@@ -205,6 +207,7 @@
 
 #	define CDECL _cdecl
 #	define WARN_FORMAT(string, args)
+#	define WARN_TIME_FORMAT(string)
 #	define FINAL final
 
 	/* fallthrough attribute, VS 2017 */

src/walltime_func.h

@@ -0,0 +1,80 @@
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
+ * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+ /** @file walltime_func.h Functionality related to the time of the clock on your wall. */
+
+#ifndef WALLTIME_FUNC_H
+#define WALLTIME_FUNC_H
+
+#include <ctime>
+
+/** Helper for safely converting a std::time_t to a local time std::tm using localtime_s. */
+struct LocalTimeToStruct {
+	static inline std::tm ToTimeStruct(std::time_t time_since_epoch)
+	{
+		std::tm time = {};
+#ifdef WIN32
+		/* Windows has swapped the parameters around for localtime_s. */
+		localtime_s(&time, &time_since_epoch);
+#else
+		localtime_r(&time_since_epoch, &time);
+#endif
+		return time;
+	}
+};
+
+/** Helper for safely converting a std::time_t to a UTC time std::tm using gmtime_s. */
+struct UTCTimeToStruct {
+	static inline std::tm ToTimeStruct(std::time_t time_since_epoch)
+	{
+		std::tm time = {};
+#ifdef WIN32
+		/* Windows has swapped the parameters around for gmtime_s. */
+		gmtime_s(&time, &time_since_epoch);
+#else
+		gmtime_r(&time_since_epoch, &time);
+#endif
+		return time;
+	}
+};
+
+/**
+ * Container for wall clock time related functionality not directly provided by C++.
+ * @tparam T The type of the time-to-struct implementation class.
+ */
+template <typename T>
+struct Time {
+	/**
+	 * Format the current time with the given strftime format specifiers.
+	 * @param buffer The buffer to write the time string to.
+	 * @param last   The last element in the buffer.
+	 * @param format The format according to strftime format specifiers.
+	 * @return The number of characters that were written to the buffer.
+	 */
+	static inline size_t Format(char *buffer, const char *last, const char *format) NOACCESS(2) WARN_TIME_FORMAT(3)
+	{
+		std::tm time_struct = T::ToTimeStruct(time(nullptr));
+#ifndef _MSC_VER
+		/* GCC bug #39438; unlike for printf where the appropriate attribute prevent the
+		 * "format non literal" warning, that does not happen for strftime. Even though
+		 * format warnings will be created for invalid strftime formats. */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wformat-nonliteral"
+#endif /* _MSC_VER */
+		return strftime(buffer, last - buffer, format, &time_struct);
+#ifndef _MSC_VER
+#pragma GCC diagnostic pop
+#endif /* _MSC_VER */
+	}
+};
+
+/** Wall clock time functionality using the local time zone. */
+using LocalTime = Time<LocalTimeToStruct>;
+/** Wall clock time functionality using the UTC time zone. */
+using UTCTime = Time<UTCTimeToStruct>;
+
+#endif