I was glancing over Annex F of the C11 spec today and I was curious if
the macro `__STDC_IEC_559__` indicating compliance is defined.
There is an open bug  about this. Richard Smith back in 2013 said
 (in a related bug) that Clang does not support Annex F. Is that
It seems with Clang (3.9) on Linux with glibc 2.24 that the
`__STDC_IEC_559__` macro is defined by glibc itself by
`/usr/include/stdc-predef.h` (gets included by clang if a glibc header
gets included like `stdio.h`).
This interaction with glibc seems like a bug so I've created a bug
report . Even though the bug is in glibc itself we need to come up
with a way to communicate clang's support for Annex F to glibc.