clar(clar_summary_testsuite): avoid thread-unsafe localtime()

The `localtime()` function is inherently thread-unsafe and should not be
used anymore. Let's use `localtime_r()` instead.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

t/unit-tests/clar/clar.c

@@ -79,6 +79,8 @@
 #	else
 #		define p_snprintf snprintf
 #	endif
+
+#	define localtime_r(timer, buf) (localtime_s(buf, timer) == 0 ? buf : NULL)
 #else
 #	include <sys/wait.h> /* waitpid(2) */
 #	include <unistd.h>

t/unit-tests/clar/clar/summary.h

@@ -23,10 +23,11 @@ static int clar_summary_testsuite(struct clar_summary *summary,
     int idn, const char *name, time_t timestamp,
     int test_count, int fail_count, int error_count)
 {
-	struct tm *tm = localtime(&timestamp);
+	struct tm tm;
 	char iso_dt[20];
 
-	if (strftime(iso_dt, sizeof(iso_dt), "%Y-%m-%dT%H:%M:%S", tm) == 0)
+	localtime_r(&timestamp, &tm);
+	if (strftime(iso_dt, sizeof(iso_dt), "%Y-%m-%dT%H:%M:%S", &tm) == 0)
 		return -1;
 
 	return fprintf(summary->fp, "\t<testsuite"