[gdm] Only call backtrace() if execinfo.h exists

[Ray Strode <halfline src gnome org>]

commit 82b84fae0912c82cbef7d3b6bfedf934db8047b8
Author: Daniel Macks <dmacks netspace org>
Date:   Thu Jul 16 23:04:21 2009 -0400

    Only call backtrace() if execinfo.h exists
    
    This fixes a build problem on OSX.
    
    See http://bugzilla.gnome.org/show_bug.cgi?id=568491

 common/gdm-signal-handler.c |    8 ++++++--
 configure.ac                |    6 ++++++
 2 files changed, 12 insertions(+), 2 deletions(-)
---
diff --git a/common/gdm-signal-handler.c b/common/gdm-signal-handler.c
index b9362b3..6b7b615 100644
--- a/common/gdm-signal-handler.c
+++ b/common/gdm-signal-handler.c
@@ -27,7 +27,9 @@
 #include <unistd.h>
 #include <string.h>
 #include <signal.h>
+#if HAVE_EXECINFO_H
 #include <execinfo.h>
+#endif
 #include <syslog.h>
 #include <sys/wait.h>
 #include <sys/stat.h>
@@ -160,6 +162,7 @@ signal_io_watch (GIOChannel       *ioc,
 static void
 fallback_get_backtrace (void)
 {
+#ifdef HAVE_EXECINFO_H
         void *  frames[64];
         size_t  size;
         char ** strings;
@@ -173,9 +176,10 @@ fallback_get_backtrace (void)
                 }
                 free (strings);
                 syslog (LOG_CRIT, "******************* END **********************************");
-        } else {
-                g_warning ("GDM crashed, but symbols couldn't be retrieved.");
+                return;
         }
+#endif
+        g_warning ("GDM crashed, but symbols couldn't be retrieved.");
 }
 
 
diff --git a/configure.ac b/configure.ac
index 22fff72..f8feddc 100644
--- a/configure.ac
+++ b/configure.ac
@@ -899,6 +899,12 @@ AC_SUBST(RBAC_LIBS)
 
 
 dnl ---------------------------------------------------------------------------
+dnl check for backtrace support
+dnl ---------------------------------------------------------------------------
+
+AC_CHECK_HEADERS(execinfo.h)
+
+dnl ---------------------------------------------------------------------------
 dnl - Define some variables to represent the directories we use.
 dnl ---------------------------------------------------------------------------