Re: [Mingw-w64-public] [PATCH 7/7] crt: Extend t_time test for _localtime64 and _mktime64

[Martin Storsjö]

On Sat, 25 Oct 2025, Pali Rohár wrote:

---
mingw-w64-crt/testcases/t_time.c | 96 ++++++++++++++++++++++++++++++--
1 file changed, 92 insertions(+), 4 deletions(-)
diff --git a/mingw-w64-crt/testcases/t_time.c b/mingw-w64-crt/testcases/t_time.c
index 50b07d0083a7..75a15d816d31 100644
--- a/mingw-w64-crt/testcases/t_time.c
+++ b/mingw-w64-crt/testcases/t_time.c
@@ -10,14 +10,17 @@ int __cdecl ftime64(struct __timeb64 *tb64);

int main()
{
-  time_t t;
-  __time32_t t32;
-  __time64_t t64;
+  time_t t, t_;
+  __time32_t t32, t32_;
+  __time64_t t64, t64_;
  struct timeb tb;
  struct _timeb tb_;
  struct __timeb32 tb32;
  struct __timeb64 tb64;
  struct tm *htm;
+  struct tm tm1;
+  struct tm tm2;
+  struct tm tm3;
  int ret1, ret2, ret3;
  const char *str;
  const wchar_t *wstr;
@@ -95,7 +98,49 @@ int main()
  assert (htm->tm_yday == 74);
  assert (htm->tm_isdst == 0);

-  /* ctime returns time string in local timezone, so set local timezone to UTC 
to have test timezone independent */
+  time_t times[] = {
+    1700000000 /* Tue Nov 14 22:13:20 UTC 2023 */,
+    1600000000 /* Sun Sep 13 12:26:40 UTC 2020 */,
+  };
+  for (size_t i = 0; i < sizeof(times)/sizeof(*times); i++) {
+    t = times[i];
+    htm = localtime (&t);
+    tm1 = *htm;
+    printf ("localtime(%lld):    sec=%d min=%d hour=%d mday=%d mon=%d year=%d 
wday=%d yday=%d isdst=%d\n",
+        (long long)t, htm->tm_sec, htm->tm_min, htm->tm_hour, htm->tm_mday, htm->tm_mon, 
htm->tm_year, htm->tm_wday, htm->tm_yday, htm->tm_isdst);
+    t_ = mktime (htm);
+    printf ("mktime(): %lld      sec=%d min=%d hour=%d mday=%d mon=%d year=%d 
wday=%d yday=%d isdst=%d\n",
+        (long long)t_, htm->tm_sec, htm->tm_min, htm->tm_hour, htm->tm_mday, htm->tm_mon, 
htm->tm_year, htm->tm_wday, htm->tm_yday, htm->tm_isdst);
+    assert (t_ == t);
+    assert (memcmp (htm, &tm1, sizeof(tm1)) == 0);
+
+    t32 = t;
+    htm = _localtime32 (&t32);
+    tm2 = *htm;
+    printf ("_localtime32(%d): sec=%d min=%d hour=%d mday=%d mon=%d year=%d wday=%d 
yday=%d isdst=%d\n",
+        t32, htm->tm_sec, htm->tm_min, htm->tm_hour, htm->tm_mday, htm->tm_mon, 
htm->tm_year, htm->tm_wday, htm->tm_yday, htm->tm_isdst);
+    t32_ = _mktime32 (htm);
+    printf ("_mktime32(): %d   sec=%d min=%d hour=%d mday=%d mon=%d year=%d wday=%d 
yday=%d isdst=%d\n",
+        t32_, htm->tm_sec, htm->tm_min, htm->tm_hour, htm->tm_mday, htm->tm_mon, 
htm->tm_year, htm->tm_wday, htm->tm_yday, htm->tm_isdst);
+    assert (t32_ == t32);
+    assert (memcmp (htm, &tm2, sizeof(tm2)) == 0);
+
+    t64 = t;
+    htm = _localtime64 (&t64);
+    tm3 = *htm;
+    printf ("_localtime64(%lld): sec=%d min=%d hour=%d mday=%d mon=%d year=%d 
wday=%d yday=%d isdst=%d\n",
+        t64, htm->tm_sec, htm->tm_min, htm->tm_hour, htm->tm_mday, htm->tm_mon, 
htm->tm_year, htm->tm_wday, htm->tm_yday, htm->tm_isdst);
+    t64_ = _mktime64 (htm);
+    printf ("_mktime64(): %lld   sec=%d min=%d hour=%d mday=%d mon=%d year=%d 
wday=%d yday=%d isdst=%d\n",
+        t64_, htm->tm_sec, htm->tm_min, htm->tm_hour, htm->tm_mday, htm->tm_mon, 
htm->tm_year, htm->tm_wday, htm->tm_yday, htm->tm_isdst);
+    assert (t64_ == t64);
+    assert (memcmp (htm, &tm3, sizeof(tm3)) == 0);
+
+    assert (memcmp (&tm1, &tm2, sizeof(tm1)) == 0);
+    assert (memcmp (&tm2, &tm3, sizeof(tm2)) == 0);
+  }
+
+  /* ctime, localtime and mktime returns time string in local timezone, so set 
local timezone to UTC to have test timezone independent */
  putenv ("TZ=UTC");

In addition to setting TZ=UTC here, is it possible to set some other 
well-known timezone that would be available everywhere, which we could use 
for some testcases for cases closer to the DST switchover time? We could 
do that for both mktime and localtime IMO.

In itself, these test additions probably are fine though - the above would 
be nice extras. But given that corner case handling close to DST 
switchovers, I think it would be good to actually check such a case.

So this patchset in itself looks ok, except for the one issue I found in 
2/7.

// Martin

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