Messages in this thread | | | Date | Fri, 20 May 2022 06:19:15 +0200 | From | Willy Tarreau <> | Subject | Re: [PATCH v1 1/2] tools/nolibc/stdlib: Support overflow checking for older compiler versions |
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Hi Ammar,
On Fri, May 20, 2022 at 12:21:15AM +0700, Ammar Faizi wrote: > diff --git a/tools/include/nolibc/stdlib.h b/tools/include/nolibc/stdlib.h > index 8fd32eaf8037..92378c4b9660 100644 > --- a/tools/include/nolibc/stdlib.h > +++ b/tools/include/nolibc/stdlib.h > @@ -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)) {
Ah, that approach is even better than mine, I'm seeing that on x86 the compiler simply checks the overflow flag after the multiply, that's perfect!
Acked-by: Willy Tarreau <w@1wt.eu>
Willy
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