Re: unexmacosx.c and limits.h problem

[Paul Eggert <eggert@cs.ucla.edu>]

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Eli Zaretskii wrote:
> Which to me sounds like lib/limits.h is not a good place to define
> these constants, or at least Emacs shouldn't rely on Gnulib's limits.h
> to do its magic on all systems.

The ISO technical spec says the settings should go into <limits.h>, and if we 
put them somewhere else that will just make things more confusing in the long run.

I installed the attached patch, which should fix the immediate problem.

The fundamental problem here is that Emacs <config.h> over the years has bloated 
to contain many things that it should not. <config.h> should always be included 
first -- this is a key assumption of Autoconf and Gnulib -- and should contain 
only stuff that can appear in an included-first file. It should therefore not 
contain things like "#include <stdlib.h>" that can cause trouble in the cases 
we're talking about.

It's understandable why config.h has bloated, as it's a convenient catchall for 
stuff that has to be visible "everywhare" at the C level. The 
visibility-"everywhere" problem needs to be addressed in some other way, that's 
all. I'll look into fixing this.

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From 8fdc22328b0932f2360f722e36a7f1ac7e5e5a20 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Sat, 17 Sep 2016 11:05:07 -0700
Subject: [PATCH] Define _GNU_SOURCE in files delaying config.h

Problem reported by Richard Copley in:
http://lists.gnu.org/archive/html/emacs-devel/2016-09/msg00440.html
* src/w32.c, src/w32notify.c, src/w32proc.c (_GNU_SOURCE):
Define early.
---
 src/unexmacosx.c | 5 +----
 src/w32.c        | 3 +++
 src/w32notify.c  | 3 +++
 src/w32proc.c    | 3 +++
 4 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/unexmacosx.c b/src/unexmacosx.c
index 2ba67df..185a9d1 100644
--- a/src/unexmacosx.c
+++ b/src/unexmacosx.c
@@ -85,11 +85,8 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
    be changed accordingly.
 */
 
-/* Make symbols like LLONG_WIDTH visible when the Gnulib <limits.h>
-   is included before <config.h>.  */
-#ifndef _GNU_SOURCE
+/* Enable GNU extensions in gnulib replacement headers.  */
 #define _GNU_SOURCE 1
-#endif
 
 /* config.h #define:s malloc/realloc/free and then includes stdlib.h.
    We want the undefined versions, but if config.h includes stdlib.h
diff --git a/src/w32.c b/src/w32.c
index 1db3426..6cb8e74 100644
--- a/src/w32.c
+++ b/src/w32.c
@@ -21,6 +21,9 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
    Geoff Voelker (voelker@cs.washington.edu)                         7-29-94
 */
 
+/* Enable GNU extensions in gnulib replacement headers.  */
+#define _GNU_SOURCE 1
+
 #include <mingw_time.h>
 #include <stddef.h> /* for offsetof */
 #include <stdlib.h>
diff --git a/src/w32notify.c b/src/w32notify.c
index d4a113a..15e8a86 100644
--- a/src/w32notify.c
+++ b/src/w32notify.c
@@ -81,6 +81,9 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
    thread to exit.  The main thread waits for some time for the worker
    thread to exit, and if it doesn't, terminates it forcibly.  */
 
+/* Enable GNU extensions in gnulib replacement headers.  */
+#define _GNU_SOURCE 1
+
 #include <stddef.h>
 #include <errno.h>
 
diff --git a/src/w32proc.c b/src/w32proc.c
index 90cef32..e23b1b3 100644
--- a/src/w32proc.c
+++ b/src/w32proc.c
@@ -22,6 +22,9 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
      Adapted from alarm.c by Tim Fleehart
 */
 
+/* Enable GNU extensions in gnulib replacement headers.  */
+#define _GNU_SOURCE 1
+
 #include <mingw_time.h>
 #include <stdio.h>
 #include <stdlib.h>
-- 
2.7.4