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From 735cc1af7595890d9cd567f36dabaf41fae4210e Mon Sep 17 00:00:00 2001
From: Mamoru TASAKA <mtasaka@fedoraproject.org>
Date: Mon, 11 Jul 2016 16:53:14 +0900
Subject: [PATCH] XIO: print C backtrace on error

For debugging purpose, show C backtrace with XIO
error happens.
---
 driver/xscreensaver.c | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/driver/xscreensaver.c b/driver/xscreensaver.c
index 76969f2..04c2669 100644
--- a/driver/xscreensaver.c
+++ b/driver/xscreensaver.c
@@ -148,10 +148,15 @@
 # include "config.h"
 #endif
 
+#include <features.h>
 #include <stdio.h>
 #include <ctype.h>
 #include <X11/Xlib.h>
 
+#ifdef __GNU_LIBRARY__
+#include <execinfo.h>
+#endif
+
 #ifdef ENABLE_NLS
 # include <locale.h>
 # include <libintl.h>
@@ -504,6 +509,41 @@ startup_ehandler (String name, String type, String class,
   exit (1);
 }
 
+static void
+show_cstyle_backtrace(void)
+{
+#ifdef __GNU_LIBRARY__
+  void *bt_array[128];
+  size_t bt_size;
+
+  bt_size = backtrace(bt_array, countof(bt_array));
+  fprintf(stderr, "C backtrace:\n");
+  backtrace_symbols_fd(bt_array, bt_size, STDERR_FILENO);
+#endif
+}
+
+static int (*default_xio_ehandler)(Display *dpy) = 0;
+
+static int
+show_debug_info_xio_ehandler(Display *dpy)
+{
+  show_cstyle_backtrace();
+  if (default_xio_ehandler){
+    (*default_xio_ehandler)(dpy);
+  }
+  return 0;
+}
+
+static void
+hack_IOErrorHandler(void)
+{
+#ifdef __GNU_LIBRARY__
+  XIOErrorHandler old_handler;
+  old_handler = XSetIOErrorHandler(show_debug_info_xio_ehandler);
+  default_xio_ehandler = old_handler;
+#endif
+}
+
 
 /* The zillions of initializations.
  */
@@ -1570,6 +1610,7 @@ main (int argc, char **argv)
 
   initialize_stderr (si);
   handle_signals (si);
+  hack_IOErrorHandler();
 
   make_splash_dialog (si);
 
-- 
2.7.4