[gtk+] Use AC_USE_SYSTEM_EXTENSIONS to get _GNU_SOURCE, _XOPEN_SOURCE etc.

[Simon McVittie <smcv src gnome org>]

commit d329544e703f3dd95be961e1d3778ee1b0dce81b
Author: Simon McVittie <smcv debian org>
Date:   Sun Aug 17 15:00:54 2014 +0100

    Use AC_USE_SYSTEM_EXTENSIONS to get _GNU_SOURCE, _XOPEN_SOURCE etc.
    
    Similar to Bug #684123 in GLib.
    
    Bug: https://bugzilla.gnome.org/show_bug.cgi?id=641638
    Bug-Debian: https://bugs.debian.org/756476
    Reviewed-by: Matthias Clasen

 configure.ac                                     |    2 ++
 gdk/wayland/gdkdevice-wayland.c                  |    1 -
 gtk/fnmatch.c                                    |    7 -------
 gtk/gtkscalebutton.c                             |    3 ---
 gtk/gtksearchenginesimple.c                      |    8 --------
 modules/printbackends/cups/gtkprintbackendcups.c |    4 ----
 6 files changed, 2 insertions(+), 23 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 4406403..a814abe 100644
--- a/configure.ac
+++ b/configure.ac
@@ -227,6 +227,8 @@ LT_INIT([disable-static win32-dll])
 # Create libtool early, because it's used in configure
 LT_OUTPUT
 
+# Define _GNU_SOURCE etc. where appropriate, e.g. for strptime() on glibc
+AC_USE_SYSTEM_EXTENSIONS
 # Make sure we use 64-bit versions of various file stuff.
 AC_SYS_LARGEFILE
 
diff --git a/gdk/wayland/gdkdevice-wayland.c b/gdk/wayland/gdkdevice-wayland.c
index 37c6a94..efe413a 100644
--- a/gdk/wayland/gdkdevice-wayland.c
+++ b/gdk/wayland/gdkdevice-wayland.c
@@ -15,7 +15,6 @@
  * License along with this library. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#define _GNU_SOURCE
 #include <unistd.h>
 #include <fcntl.h>
 #include <errno.h>
diff --git a/gtk/fnmatch.c b/gtk/fnmatch.c
index e67052b..87582ca 100644
--- a/gtk/fnmatch.c
+++ b/gtk/fnmatch.c
@@ -35,13 +35,6 @@
 
 #include <glib.h>
 
-/* We need to make sure that all constants are defined
- * to properly compile this file
- */
-#ifndef _GNU_SOURCE
-#define _GNU_SOURCE
-#endif
-
 static gunichar
 get_char (const char **str)
 {
diff --git a/gtk/gtkscalebutton.c b/gtk/gtkscalebutton.c
index b4bda76..c979f61 100644
--- a/gtk/gtkscalebutton.c
+++ b/gtk/gtkscalebutton.c
@@ -36,9 +36,6 @@
 
 #include "gtkscalebutton.h"
 
-#ifndef _WIN32
-#define _GNU_SOURCE
-#endif
 #include <math.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/gtk/gtksearchenginesimple.c b/gtk/gtksearchenginesimple.c
index 1475058..4d8ff2f 100644
--- a/gtk/gtksearchenginesimple.c
+++ b/gtk/gtksearchenginesimple.c
@@ -21,14 +21,6 @@
 
 #include "config.h"
 
-/* these must be defined even when HAVE_GNU_FTW is not defined
- * because (really) old versions of GNU libc have ftw.h but do
- * export ftw() and friends only if _XOPEN_SOURCE and _GNU_SOURCE
- * are defined. see bug #444097.
- */
-#define _XOPEN_SOURCE 600
-#define _GNU_SOURCE
-
 #ifdef HAVE_FTW_H
 #include <ftw.h>
 #endif
diff --git a/modules/printbackends/cups/gtkprintbackendcups.c 
b/modules/printbackends/cups/gtkprintbackendcups.c
index a49bb2d..69abd49 100644
--- a/modules/printbackends/cups/gtkprintbackendcups.c
+++ b/modules/printbackends/cups/gtkprintbackendcups.c
@@ -17,10 +17,6 @@
  * License along with this library. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifdef __linux__
-#define _GNU_SOURCE
-#endif
-
 #include "config.h"
 #include <ctype.h>
 #include <unistd.h>