[Bug c/66970] Add __has_builtin() macro

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66970

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #24 from Martin Sebor <msebor at gcc dot gnu.org> ---
Committed in r277544.

Unlike in Clang, arguments to the GCC __has_builtin operator are subject to
macro expansion.  Also unlike in Clang (as of today), in GCC __has_builtin
(__is_aggregate) && __has_builtin (__builtin_launder) && __has_builtin
(__builtin_offsetof) evaluates to non-zero.