[Bug c/68868] atomic_init emits an unnecessary fence

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68868

--- Comment #2 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
On Sat, 12 Dec 2015, msebor at gcc dot gnu.org wrote:

> +      __typeof__ (VALUE) __tmp = (VALUE);                         \

Using typeof like this is incorrect; it results in multiple evaluation if 
VALUE has a variably modified type.  You have to use __auto_type in such a 
case, as elsewhere in stdatomic.h.