http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49595
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-06-30 17:42:59 UTC --- sizeof(intmax_t) is fixed by various LP64 ABIs and cannot be changed I believe the stock answer is that __int128 is not a C99 extended integer type, so isn't one of the types that intmax_t can represent the value of