bug#23640: 25.1.50; Getting rid of compiler warnings

[Eli Zaretskii]

> From: Ken Brown <kbrown@cornell.edu>
> Date: Sat, 28 May 2016 14:40:36 -0400
> 
> Building master on Cygwin with gcc-5.3.0 yields many "control reaches
> end of non-void function" warnings.  What's the best way to get rid of
> these?  Should I add return statements that will never be reached, like
> this?
> 
> --- a/src/frame.c
> +++ b/src/frame.c
> @@ -263,6 +263,8 @@ See also `frame-live-p'.  */)
>         return Qns;
>       default:
>         emacs_abort ();
> +      /* Pacify compiler.  */
> +      return Qnil;
>       }
>   }

emacs_abort is declared with _Noreturn, so how come GCC doesn't shut
up about "unreachable" code?

FWIW, I'm building master with GCC 5.3.0, and don't see these
warnings.