[PATCH] Use mingw.h declarations for gmtime_r/localtime_r on msys2

[Mike Hommey <mh@glandium.org>]

Older versions of msys2 had _POSIX_THREAD_SAFE_FUNCTIONS set in
pthread_unistd.h, included from unistd.h. That would enable the
declarations for gmtime_r and localtime_r in time.h.

That's not the case anymore, and gmtime_r and localtime_r end up
being undeclared, which subsequently leads to "miscompilations", for
example, in datestamp(), where the result of localtime_r would be
truncated and sign-extended before being passed to tm_to_time_t, leading
to segfaults at runtime.

Signed-off-by: Mike Hommey <mh@glandium.org>
---
 compat/mingw.h | 2 --
 1 file changed, 2 deletions(-)

A possible alternative fix would be to e.g. add `#define _POSIX_C_SOURCE
200112L` to git-compat-util.h and add `ifndef __MINGW64_VERSION_MAJOR`
around the definitions of `gmtime_r` and `localtime_r` in
compat/mingw.c, since, after all, they are available there.

diff --git a/compat/mingw.h b/compat/mingw.h
index c9a52ad64a..4fd989980c 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -204,10 +204,8 @@ int pipe(int filedes[2]);
 unsigned int sleep (unsigned int seconds);
 int mkstemp(char *template);
 int gettimeofday(struct timeval *tv, void *tz);
-#ifndef __MINGW64_VERSION_MAJOR
 struct tm *gmtime_r(const time_t *timep, struct tm *result);
 struct tm *localtime_r(const time_t *timep, struct tm *result);
-#endif
 int getpagesize(void);	/* defined in MinGW's libgcc.a */
 struct passwd *getpwuid(uid_t uid);
 int setitimer(int type, struct itimerval *in, struct itimerval *out);
-- 
2.33.0