mingw: use {gm,local}time_s as backend for {gm,local}time_r

sgn · gitster · commit 0109d676f9d4 · 2019-12-01T22:26:25.000-08:00
Since Windows doesn't provide gmtime_r(3) and localtime_r(3),
we're providing a compat version by using non-reentrant gmtime(3) and
localtime(3) as backend. Then, we copy the returned data into the
buffer.

By doing that, in case of failure, we will dereference a NULL pointer
returned by gmtime(3), and localtime(3), and we always return a valid
pointer instead of NULL.

Drop the memcpy(3) by using gmtime_s(), and use localtime_s() as the
backend on Windows, and make sure we will return NULL in case of
failure.

Cc: Johannes Sixt &lt;j6t@kdbg.org&gt;
Cc: Johannes Schindelin &lt;Johannes.Schindelin@gmx.de&gt;
Signed-off-by: Doan Tran Cong Danh &lt;congdanhqx@gmail.com&gt;
Signed-off-by: Junio C Hamano &lt;gitster@pobox.com&gt;
diff --git a/compat/mingw.c b/compat/mingw.c
@@ -986,16 +986,16 @@ int pipe(int filedes[2])
 
 struct tm *gmtime_r(const time_t *timep, struct tm *result)
 {
-	/* gmtime() in MSVCRT.DLL is thread-safe, but not reentrant */
-	memcpy(result, gmtime(timep), sizeof(struct tm));
-	return result;
+	if (gmtime_s(result, timep) == 0)
+		return result;
+	return NULL;
 }
 
 struct tm *localtime_r(const time_t *timep, struct tm *result)
 {
-	/* localtime() in MSVCRT.DLL is thread-safe, but not reentrant */
-	memcpy(result, localtime(timep), sizeof(struct tm));
-	return result;
+	if (localtime_s(result, timep) == 0)
+		return result;
+	return NULL;
 }
 
 char *mingw_getcwd(char *pointer, int len)

Original file line number	Diff line number	Diff line change
`@@ -986,16 +986,16 @@ int pipe(int filedes[2])`
`986`	`986`
`987`	`987`	`struct tm gmtime_r(const time_t timep, struct tm *result)`
`988`	`988`	`{`
`989`		`- /* gmtime() in MSVCRT.DLL is thread-safe, but not reentrant */`
`990`		`- memcpy(result, gmtime(timep), sizeof(struct tm));`
`991`		`- return result;`
	`989`	`+ if (gmtime_s(result, timep) == 0)`
	`990`	`+ return result;`
	`991`	`+ return NULL;`
`992`	`992`	`}`
`993`	`993`
`994`	`994`	`struct tm localtime_r(const time_t timep, struct tm *result)`
`995`	`995`	`{`
`996`		`- /* localtime() in MSVCRT.DLL is thread-safe, but not reentrant */`
`997`		`- memcpy(result, localtime(timep), sizeof(struct tm));`
`998`		`- return result;`
	`996`	`+ if (localtime_s(result, timep) == 0)`
	`997`	`+ return result;`
	`998`	`+ return NULL;`
`999`	`999`	`}`
`1000`	`1000`
`1001`	`1001`	`char mingw_getcwd(char pointer, int len)`