Add portability wrapper for localtime_r()

ConfigureChecks.cmake

@@ -83,6 +83,10 @@ endif()
 check_symbol_exists("clock_gettime"  "time.h"   HAVE_CLOCK_GETTIME)
 # Some platforms (macOS pre 10.15) are non-conformant with C11 and lack timespec_get()
 check_symbol_exists("timespec_get"   "time.h"   HAVE_TIMESPEC_GET)
+if(NOT MSVC)
+	check_symbol_exists("localtime_r"    "time.h"   HAVE_LOCALTIME_R)
+	check_symbol_exists("tzset"          "time.h"   HAVE_TZSET)
+endif()
 check_function_exists("getifaddrs"       HAVE_GETIFADDRS)
 check_function_exists("issetugid"        HAVE_ISSETUGID)
 check_function_exists("setresgid"        HAVE_SETRESGID)

cmakeconfig.h.in

@@ -49,6 +49,12 @@
 /* Define to 1 if you have the `timespec_get` function. */
 #cmakedefine HAVE_TIMESPEC_GET 1
 
+/* Define to 1 if you have the `localtime_r` function. */
+#cmakedefine HAVE_LOCALTIME_R 1
+
+/* Define to 1 if you have the `tzset` function. */
+#cmakedefine HAVE_TZSET 1
+
 /* Define to use the MaxMind DB library */
 #cmakedefine HAVE_MAXMINDDB 1
 

wsutil/time_util.c

@@ -250,6 +250,28 @@ char *ws_strptime(const char *restrict s, const char *restrict format,
 #endif
 }
 
+struct tm *
+ws_localtime_r(const time_t *timep, struct tm *result)
+{
+#if defined(HAVE_LOCALTIME_R)
+#ifdef HAVE_TZSET
+	tzset();
+#endif
+	return localtime_r(timep, result);
+#elif defined(_MSC_VER)
+	errno_t err = localtime_s(result, timep);
+	if (err == 0)
+		return result;
+	return NULL;
+#else
+	struct tm *aux = localtime(timep);
+	if (aux == NULL)
+		return NULL;
+	*result = *aux;
+	return result;
+#endif
+}
+
 /*
  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
  *

wsutil/time_util.h

@@ -71,6 +71,9 @@ struct timespec *ws_clock_get_realtime(struct timespec *ts);
 WS_DLL_PUBLIC
 char *ws_strptime(const char *s, const char *format, struct tm *tm);
 
+WS_DLL_PUBLIC
+struct tm *ws_localtime_r(const time_t *timep, struct tm *result);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */