[patch] For BZ #17328, mark __errno_location with __attribute__((returns_nonnull)) for gcc >=4.9.0

[Rich Felker]

On Tue, Mar 03, 2015 at 03:42:48AM +0000, Joseph Myers wrote:
> On Mon, 2 Mar 2015, Roland McGrath wrote:
> 
> > Then a savvy user could '#undef errno' to use the TLS version.  We could
> 
> I don't think we should encourage users to #undef errno (something 
> undefined in ISO C, and that wouldn't work with current glibc).

Agree. This is a really nasty idea. If such a feature is to be
exposed, it should be via a feature test macro, not UB hacks.

Rich