* font.c (valid_font_driver) [ENABLE_CHECKING]: New function

intended to find bogus pointers in font objects (Bug#16140).
* font.h (valid_font_driver) [ENABLE_CHECKING]: Add prototype.
* alloc.c (cleanup_vector): Use valid_font_driver in eassert.
(compact_font_cache_entry, compact_font_caches) [!HAVE_NTGUI]:
Disable for MS-Windows due to Bug#15876; apparently this
requires more or less substantial changes in fontset code.
* xfont.c (xfont_close):
* xftfont.c (xftfont_close): Call x_display_info_for_display
to check whether 'Display *' is valid (Bug#16093 and probably
Bug#16069).

6 files changed, 58 insertions, 5 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index d5c84d04807..7b8a624d629 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,17 @@
+2013-12-16  Dmitry Antipov  <dmantipov@yandex.ru>
+
+	* font.c (valid_font_driver) [ENABLE_CHECKING]: New function
+	intended to find bogus pointers in font objects (Bug#16140).
+	* font.h (valid_font_driver) [ENABLE_CHECKING]: Add prototype.
+	* alloc.c (cleanup_vector): Use valid_font_driver in eassert.
+	(compact_font_cache_entry, compact_font_caches) [!HAVE_NTGUI]:
+	Disable for MS-Windows due to Bug#15876; apparently this
+	requires more or less substantial changes in fontset code.
+	* xfont.c (xfont_close):
+	* xftfont.c (xftfont_close): Call x_display_info_for_display
+	to check whether 'Display *' is valid (Bug#16093 and probably
+	Bug#16069).
+
 2013-12-15  Eli Zaretskii  <eliz@gnu.org>
 
 	* fileio.c (Fexpand_file_name) [WINDOWSNT]: Fix conditionals.
diff --git a/src/alloc.c b/src/alloc.c
index aeda42637cd..447b465a076 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -2877,7 +2877,11 @@ cleanup_vector (struct Lisp_Vector *vector)
   if (PSEUDOVECTOR_TYPEP (&vector->header, PVEC_FONT)
       && ((vector->header.size & PSEUDOVECTOR_SIZE_MASK)
 	  == FONT_OBJECT_MAX))
-    ((struct font *) vector)->driver->close ((struct font *) vector);
+    {
+      /* Attempt to catch subtle bugs like Bug#16140.  */
+      eassert (valid_font_driver (((struct font *) vector)->driver));
+      ((struct font *) vector)->driver->close ((struct font *) vector);
+    }
 }
 
 /* Reclaim space used by unmarked vectors.  */
@@ -5299,6 +5303,10 @@ total_bytes_of_live_objects (void)
 
 #ifdef HAVE_WINDOW_SYSTEM
 
+/* This code has a few issues on MS-Windows, see Bug#15876 and Bug#16140.  */
+
+#if !defined (HAVE_NTGUI)
+
 /* Remove unmarked font-spec and font-entity objects from ENTRY, which is
    (DRIVER-TYPE NUM-FRAMES FONT-CACHE-DATA ...), and return changed entry.  */
 
@@ -5337,6 +5345,8 @@ compact_font_cache_entry (Lisp_Object entry)
   return entry;
 }
 
+#endif /* not HAVE_NTGUI */
+
 /* Compact font caches on all terminals and mark
    everything which is still here after compaction.  */
 
@@ -5348,7 +5358,7 @@ compact_font_caches (void)
   for (t = terminal_list; t; t = t->next_terminal)
     {
       Lisp_Object cache = TERMINAL_FONT_CACHE (t);
-
+#if !defined (HAVE_NTGUI)
       if (CONSP (cache))
 	{
 	  Lisp_Object entry;
@@ -5356,6 +5366,7 @@ compact_font_caches (void)
 	  for (entry = XCDR (cache); CONSP (entry); entry = XCDR (entry))
 	    XSETCAR (entry, compact_font_cache_entry (XCAR (entry)));
 	}
+#endif /* not HAVE_NTGUI */
       mark_object (cache);
     }
 }
diff --git a/src/font.c b/src/font.c
index fb56b3d3fb3..db55549be8c 100644
--- a/src/font.c
+++ b/src/font.c
@@ -148,7 +148,27 @@ static Lisp_Object font_charset_alist;
    here.  */
 static struct font_driver_list *font_driver_list;
 
-
+#ifdef ENABLE_CHECKING
+
+/* Used to catch bogus pointers in font objects.  */
+
+bool
+valid_font_driver (struct font_driver *drv)
+{
+  Lisp_Object tail, frame;
+  struct font_driver_list *fdl;
+
+  for (fdl = font_driver_list; fdl; fdl = fdl->next)
+    if (fdl->driver == drv)
+      return true;
+  FOR_EACH_FRAME (tail, frame)
+    for (fdl = XFRAME (frame)->font_driver_list; fdl; fdl = fdl->next)
+      if (fdl->driver == drv)
+	return true;
+  return false;
+}
+
+#endif /* ENABLE_CHECKING */
 
 /* Creators of font-related Lisp object.  */
 
diff --git a/src/font.h b/src/font.h
index 2c7456a2f29..8fb80a9b617 100644
--- a/src/font.h
+++ b/src/font.h
@@ -787,6 +787,9 @@ extern int font_unparse_fcname (Lisp_Object font, int pixel_size,
                                 char *name, int bytes);
 extern void register_font_driver (struct font_driver *driver, struct frame *f);
 extern void free_font_driver_list (struct frame *f);
+#ifdef ENABLE_CHECKING
+extern bool valid_font_driver (struct font_driver *);
+#endif
 extern Lisp_Object font_update_drivers (struct frame *f, Lisp_Object list);
 extern Lisp_Object font_range (ptrdiff_t, ptrdiff_t, ptrdiff_t *,
 			       struct window *, struct face *,
diff --git a/src/xfont.c b/src/xfont.c
index d4d6ee7c10f..df69c9141bd 100644
--- a/src/xfont.c
+++ b/src/xfont.c
@@ -894,7 +894,10 @@ xfont_close (struct font *font)
 {
   struct xfont_info *xfi = (struct xfont_info *) font;
 
-  if (xfi->xfont)
+  /* This function may be called from GC when X connection is gone
+     (Bug#16093), and an attempt to free font resourses on invalid
+     display may lead to X protocol errors or segfaults.  */
+  if (xfi->xfont && x_display_info_for_display (xfi->display))
     {
       block_input ();
       XFreeFont (xfi->display, xfi->xfont);
diff --git a/src/xftfont.c b/src/xftfont.c
index 37b33b3ead8..178981c4958 100644
--- a/src/xftfont.c
+++ b/src/xftfont.c
@@ -491,7 +491,9 @@ xftfont_close (struct font *font)
     }
 #endif
 
-  if (xftfont_info->xftfont)
+  /* See comment in xfont_close.  */
+  if (xftfont_info->xftfont
+      && x_display_info_for_display (xftfont_info->display))
     {
       block_input ();
       XftUnlockFace (xftfont_info->xftfont);