[Bug c/49595] on amd64, sizeof(__int128_t) > sizeof(intmax_t)

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49595

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-06-30 18:29:02 UTC ---
(In reply to comment #3)
> Since the standard specifies intmax_t in terms of a "signed integer type", it
> therefore includes any implementation-defined extended signed integer types,

Yes.

> including __int128_t.

You're assuming __int128 is an implementation-defined extended integer type.
If GCC chooses to call __int128 some other type that doesn't fall under the C99
definition of "implementation defined integer type" then intmax_t doesn't have
to be able to represent its values.

Of course this is cheating by playing wordgames, but sizeof(intmax_t) can't
change and people want to be able to use __int128