https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69560
--- Comment #20 from joseph at codesourcery dot com <joseph at codesourcery dot com> --- I consider it part of the ABI that long long __attribute__((__aligned__(__alignof__(long long)))), as in the definition of max_align_t (and similarly in gnulib's max_align_t definition, for example), is 8-byte-aligned on x86.