Re: unexmacosx.c and limits.h problem

[Eli Zaretskii <eliz@gnu.org>]

> From: Richard Copley <rcopley@gmail.com>
> Date: Sat, 17 Sep 2016 12:31:36 +0100
> Cc: Paul Eggert <eggert@cs.ucla.edu>, Bob Halley <halley@play-bow.org>, 
> 	Emacs Development <emacs-devel@gnu.org>
> 
> >>> >> +#ifndef _GNU_SOURCE
> >>> >> +#define _GNU_SOURCE 1
> >>> >> +#endif
> >>> >
> >>> >
> >>> > Thanks, I installed that into Emacs master.
> >>>
> >>> The Windows build is broken too (with MSYS2), presumably for a similar
> >>> reason.
> >>
> >> It isn't broken here.  Can you show the error messages?
> >
> > Sure, give me a few minutes. Did you reconfigure? You need the
> > generated limits.h.
> 
> Also, this is with 64-bit GCC 6.1.0.
> 
> In file included from G:/emacs/repo/emacs/src/w32.c:87:0:
> G:/emacs/repo/emacs/src/lisp.h:93:26: error: 'LLONG_WIDTH' undeclared
> here (not in a function)
>  enum { EMACS_INT_WIDTH = LLONG_WIDTH };
>                           ^~~~~~~~~~~
> 
> In file included from G:/emacs/repo/emacs/src/w32proc.c:54:0:
> G:/emacs/repo/emacs/src/lisp.h:93:26: error: 'LLONG_WIDTH' undeclared
> here (not in a function)
>  enum { EMACS_INT_WIDTH = LLONG_WIDTH };
>                           ^~~~~~~~~~~

I don't understand how this could happen.  Take w32proc.c, for
example: it includes config.h _before_ lisp.h, and on my system
config.h has these:

  /* Enable GNU extensions on systems that have them.  */
  #ifndef _GNU_SOURCE
  # define _GNU_SOURCE 1
  #endif
  [...]
  /* Enable extensions specified by ISO/IEC TS 18661-1:2014.  */
  #ifndef __STDC_WANT_IEC_60559_BFP_EXT__
  # define __STDC_WANT_IEC_60559_BFP_EXT__ 1
  #endif

So by the time limits.h gets included (via lib/stdint.h, which is
included by nt/inc/stdint.h, which is included by nt/inc/ms-w32.h),
both _GNU_SOURCE and __STDC_WANT_IEC_60559_BFP_EXT__ are already
defined, and the definitions of LLONG_WIDTH in lib/limits.h should
have been processed.

Which part(s) of this don't work on your system, and why?

To find out what happens during preprocessing, I did this:

  cd src
  make w32proc.o -W w32proc.c V=1

Then I copied the command displayed by Make, replaced -c with -E,
appended "-o w32proc.ii", ran the command, and looked inside
w32proc.ii to see how the preprocessor included the various headers
and defined the macros.

(My GCC version is 5.3.0, and this is a 32-bit build with wide ints.)