[gdm/wip/longjmp-off-a-short-bridge] wip! Add some gross longjmp code that I don't want to use

[Ray Strode <halfline src gnome org>]

commit 87448650f98d1677772f73dd8b5796af68650941
Author: Ray Strode <rstrode redhat com>
Date:   Mon Dec 12 10:37:40 2016 -0500

    wip! Add some gross longjmp code that I don't want to use

 daemon/gdm-xerrors.c |   43 ++++++++++++++++++++++++++++++++++++++++++-
 daemon/gdm-xerrors.h |    5 +++++
 2 files changed, 47 insertions(+), 1 deletions(-)
---
diff --git a/daemon/gdm-xerrors.c b/daemon/gdm-xerrors.c
index 44f567e..1fdfbc2 100644
--- a/daemon/gdm-xerrors.c
+++ b/daemon/gdm-xerrors.c
@@ -24,6 +24,7 @@
 #include <glib/gstdio.h>
 #include <errno.h>
 #include <stdlib.h>
+#include <setjmp.h>
 
 #include "gdm-xerrors.h"
 
@@ -36,6 +37,11 @@ struct _GdmErrorTrap
         int error_code;
 };
 
+struct _GdmIOErrorTrap
+{
+        int (*old_handler) (Display *);
+};
+
 static int          gdm_x_error                  (Display     *display,
                                                   XErrorEvent *error);
 static int          gdm_x_io_error               (Display     *display);
@@ -47,7 +53,6 @@ static GSList *gdm_error_trap_free_list = NULL;      /* Free list */
 
 static int                _gdm_error_warnings = TRUE;
 static int                _gdm_error_code = 0;
-
 void
 gdm_xerrors_init (void)
 {
@@ -240,3 +245,39 @@ gdm_error_trap_pop (void)
 
         return result;
 }
+
+static jmp_buf gdm_jmp_buf;
+
+static enum {
+    NO_EXCEPTION = 0,
+    EXCEPTION = 1,
+    FINISHED = 2
+} gdm_jmp_state;
+
+#define TRY if ((gdm_jmp_state = setjmp (gdm_jmp_buf)) == NO_EXCEPTION)
+#define EXCEPT if (gdm_jmp_state == NO_EXCEPTION) longjmp (gdm_jmp_buf, FINISHED); else
+
+#define THROW() longjmp (gdm_jmp_buf, EXCEPTION)
+
+static int
+gdm_trapped_x_io_error (Display *display)
+{
+        THROW ();
+}
+
+void
+gdm_trap_xserver_hangup (GdmTrappedFunc trapped_func,
+                         gpointer       data)
+{
+        int (*old_handler) (Display *) = NULL;
+
+        TRY {
+                old_handler = XSetIOErrorHandler (gdm_trapped_x_io_error);
+
+                trapped_func (data);
+
+                XSetIOErrorHandler (old_handler);
+        } EXCEPT {
+                XSetIOErrorHandler (old_handler);
+        }
+}
diff --git a/daemon/gdm-xerrors.h b/daemon/gdm-xerrors.h
index fc7981e..d2208a1 100644
--- a/daemon/gdm-xerrors.h
+++ b/daemon/gdm-xerrors.h
@@ -31,9 +31,14 @@ typedef void (* GdmXErrorHandler) (Display     *dpy,
                                    XErrorEvent *error,
                                    gpointer     data);
 
+typedef void (* GdmTrappedFunc) (gpointer *data);
+
 void      gdm_xerrors_init    (void);
 
 void      gdm_error_trap_push (void);
 gint      gdm_error_trap_pop  (void);
 
+void      gdm_trap_xserver_hangup (GdmTrappedFunc trapped_func,
+                                   gpointer       data);
+
 #endif