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

[Rich Felker]

On Sat, Feb 28, 2015 at 02:03:11PM -0800, Paul Pluzhnikov wrote:
> Greetings,
> 
> Tested on Linux/x86_64 with gcc-4.8 and 5.0.

No objection, but I'm curious if there's any practical benefit of
this. I can't think of many situations where knowledge that
&errno!=NULL would assist the compiler in optimizing or diagnostics.

Rich