On 04/02/2015 01:06 PM, H.J. Lu wrote: > On Thu, Apr 2, 2015 at 1:46 AM, Florian Weimer <fwei...@redhat.com> wrote: >> On 04/02/2015 10:40 AM, Andrew Haley wrote: >> >>> So, max_align_t is an object type, and therefore malloc returns a >>> pointer suitable for max_align_t. >> >> Then the GCC definition of max_align_t is incorrect, it should be 8 on >> x86_64 GNU/Linux, because traditionally, that's what mallocs implement >> for this architecture. (dlmalloc in glibc is an exception.) >> > > x86-64 psABI specifies that a memory >= 16 bytes is 16-byte aligned. > If malloc doesn't do it, it is a broken.
My concern is different. I think _Alignof (max_align_t) == 16 (as it is in GCC now) implies that malloc return values for sizes less than 16 bytes are 16-byte-aligned, too, which is not required by the x86-64 psABI. -- Florian Weimer / Red Hat Product Security
