the big time handling overhaul

this commit has two major user-visible parts: zoneinfo-format time
zones are now supported, and overflow handling is intended to be
complete in the sense that all functions return a correct result if
and only if the result fits in the destination type, and otherwise
return an error. also, some noticable bugs in the way DST detection
and normalization worked have been fixed, and performance may be
better than before, but it has not been tested.

1 files changed, 14 insertions, 7 deletions

diff --git a/src/time/gmtime_r.c b/src/time/gmtime_r.c
index 13a2548f..0272870d 100644
--- a/src/time/gmtime_r.c
+++ b/src/time/gmtime_r.c
@@ -1,10 +1,17 @@
-#include <time.h>
+#include "time_impl.h"
+#include <errno.h>
+#include "libc.h"
 
-#include "__time.h"
-
-struct tm *gmtime_r(const time_t *restrict t, struct tm *restrict result)
+struct tm *__gmtime_r(const time_t *restrict t, struct tm *restrict tm)
 {
-	__time_to_tm(*t, result);
-	result->tm_isdst = 0;
-	return result;
+	if (__secs_to_tm(*t, tm) < 0) {
+		errno = EINVAL;
+		return 0;
+	}
+	tm->tm_isdst = 0;
+	tm->__tm_gmtoff = 0;
+	tm->__tm_zone = "GMT";
+	return tm;
 }
+
+weak_alias(__gmtime_r, gmtime_r);