wrapper: avoid undefined behaviour in macOS

0620b39 ("compat: add a mkstemps() compatibility function", 2009-05-31)
included a function based on code from libiberty which would result in
undefined behaviour in platforms where timeval's tv_usec is a 32-bit signed
type as shown by:

wrapper.c:505:31: runtime error: left shift of 594546 by 16 places cannot be represented in type '__darwin_suseconds_t' (aka 'int')

interestingly the version of this code from gcc never had this bug and the
code had a cast that would had prevented the issue (at least in 64-bit
platforms) but was misapplied.

change the cast to uint64_t so it also works in 32-bit platforms.

Signed-off-by: Carlo Marcelo Arenas Belón <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: carenas

wrapper.c

@@ -502,7 +502,7 @@ int git_mkstemps_mode(char *pattern, int suffix_len, int mode)
 	 * Try TMP_MAX different filenames.
 	 */
 	gettimeofday(&tv, NULL);
-	value = ((size_t)(tv.tv_usec << 16)) ^ tv.tv_sec ^ getpid();
+	value = ((uint64_t)tv.tv_usec << 16) ^ tv.tv_sec ^ getpid();
 	filename_template = &pattern[len - 6 - suffix_len];
 	for (count = 0; count < TMP_MAX; ++count) {
 		uint64_t v = value;