On Thu, Apr 2, 2015 at 4:08 AM, Florian Weimer <fwei...@redhat.com> wrote: > 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. >
If you take this way, malloc of 1 byte can return 1-byte aligned memory. -- H.J.
