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tools/nolibc/stdlib: Support overflow checking for older compiler versions

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Previously, we used __builtin_mul_overflow() to check for overflow in
the multiplication operation in the calloc() function. However, older
compiler versions don't support this built-in. This patch changes the
overflow checking mechanism to make it work on any compiler version
by using a division method to check for overflow. No functional change
intended. While in there, remove the unused variable `void *orig`.

Link: https://lore.kernel.org/lkml/20220330024114.GA18892@1wt.eu
Suggested-by: Willy Tarreau <w@1wt.eu>
Cc: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org>
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
Acked-by: Willy Tarreau <w@1wt.eu>
Reviewed-by: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Ammar Faizi 2022-05-20 00:21:15 +07:00 committed by Paul E. McKenney
parent a111daf0c5
commit 1ef150cf40
1 changed files with 3 additions and 4 deletions
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7
tools/include/nolibc/stdlib.h
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@ -128,10 +128,9 @@ void *malloc(size_t len)
static __attribute__((unused))
void *calloc(size_t size, size_t nmemb)
{
void *orig;
size_t res = 0;
size_t x = size * nmemb;
if (__builtin_expect(__builtin_mul_overflow(nmemb, size, &res), 0)) {
if (__builtin_expect(size && ((x / size) != nmemb), 0)) {
SET_ERRNO(ENOMEM);
return NULL;
}
@ -140,7 +139,7 @@ void *calloc(size_t size, size_t nmemb)
* No need to zero the heap, the MAP_ANONYMOUS in malloc()
* already does it.
*/
return malloc(res);
return malloc(x);
}
static __attribute__((unused))