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.

1 files changed, 80 insertions, 0 deletions

diff --git a/src/walltime_func.h b/src/walltime_func.h
new file mode 100644
index 000000000..219a8907d
--- /dev/null
+++ b/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