Add C11 localtime_r and gmtime_r shims for Windows

On Windows, C11 localtime_r() and gmtime_r() functions are not
available.  While localtime() and gmtime() functions are already thread
safe because they use Thread Local Storage, it's quite ugly to #ifdef
around every localtime_r() and gmtime_r() usage to make the usage also
thread-safe on POSIX platforms.

The commit adds wrappers around Windows localtime_s() and gmtime_s()
functions.

NOTE: The implementation of localtime_s and gmtime_s in Microsoft CRT
are incompatible with the C standard since it has reversed parameter
order and errno_t return type.

(cherry picked from commit 08f4c7d6c0)

lib/dns/gen-win32.h

@@ -62,6 +62,7 @@
 #include <stdbool.h>
 #include <stdio.h>
 #include <string.h>
+#include <time.h>
 #include <windows.h>
 
 #include <isc/lang.h>
@@ -277,6 +278,16 @@ end_directory(isc_dir_t *dir) {
 	}
 }
 
+inline struct tm *
+gmtime_r(const time_t *clock, struct tm *result) {
+	errno_t ret = gmtime_s(result, clock);
+	if (ret != 0) {
+		errno = ret;
+		return (NULL);
+	}
+	return (result);
+}
+
 ISC_LANG_ENDDECLS
 
 #endif /* DNS_GEN_WIN32_H */

lib/dns/gen.c

@@ -700,11 +700,7 @@ main(int argc, char **argv) {
 	}
 
 	if (now != -1) {
-#ifdef _MSC_VER
-		struct tm *tm = gmtime(&now); /* Thread specific. */
-#else
 		struct tm t, *tm = gmtime_r(&now, &t);
-#endif
 
 		if (tm != NULL && tm->tm_year > 104) {
 			n = snprintf(year, sizeof(year), "-%d",

lib/dns/update.c

@@ -2191,14 +2191,10 @@ failure:
 
 static isc_stdtime_t
 epoch_to_yyyymmdd(time_t when) {
-	struct tm *tm;
-
-#if !defined(WIN32)
-	struct tm tm0;
-	tm = localtime_r(&when, &tm0);
-#else  /* if !defined(WIN32) */
-	tm = localtime(&when);
-#endif /* if !defined(WIN32) */
+	struct tm t, *tm = localtime_r(&when, &t);
+	if (tm == NULL) {
+		return (0);
+	}
 	return (((tm->tm_year + 1900) * 10000) + ((tm->tm_mon + 1) * 100) +
 		tm->tm_mday);
 }

lib/isc/win32/include/isc/time.h

@@ -12,6 +12,7 @@
 #ifndef ISC_TIME_H
 #define ISC_TIME_H 1
 
+#include <errno.h>
 #include <inttypes.h>
 #include <stdbool.h>
 #include <windows.h>
@@ -19,6 +20,30 @@
 #include <isc/lang.h>
 #include <isc/types.h>
 
+/***
+ *** POSIX Shims
+ ***/
+
+inline struct tm *
+gmtime_r(const time_t *clock, struct tm *result) {
+	errno_t ret = gmtime_s(result, clock);
+	if (ret != 0) {
+		errno = ret;
+		return (NULL);
+	}
+	return (result);
+}
+
+inline struct tm *
+localtime_r(const time_t *clock, struct tm *result) {
+	errno_t ret = localtime_s(result, clock);
+	if (ret != 0) {
+		errno = ret;
+		return (NULL);
+	}
+	return (result);
+}
+
 /***
  *** Intervals
  ***/