Commit 1ef150cf authored May 20, 2022 by Ammar Faizi Committed by Paul E. McKenney Jun 20, 2022

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

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>

parent a111daf0

tools/include/nolibc/stdlib.h

+3 −4

Original line number	Diff line number	Diff line
		@@ -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))