From: Eli Zaretskii <eliz@gnu.org>
Date: Sat, 17 Oct 2015 12:10:58 +0000 (+0300)
Subject: Avoid crashes when redisplayng a window changes faces or fonts
X-Git-Tag: emacs-25.0.90~1099
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=1431f667504b610471257802aa2f2f4f0d8443de;p=emacs.git

Avoid crashes when redisplayng a window changes faces or fonts

* src/xdisp.c (redisplay_internal): If redisplaying the selected
window or one of the frames turns on the frame's 'redisplay' flag,
redisplay again.  (Bug#21428)

* src/frame.c (x_set_font): Set the frame's 'fonts_changed' flag.
---

diff --git a/src/frame.c b/src/frame.c
index 98a7a57a988..6d596a48e23 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -3651,6 +3651,10 @@ x_set_font (struct frame *f, Lisp_Object arg, Lisp_Object oldval)
   /* Attempt to hunt down bug#16028.  */
   SET_FRAME_GARBAGED (f);
 
+  /* This is important if we are called by some Lisp as part of
+     redisplaying the frame, see redisplay_internal.  */
+  f->fonts_changed = true;
+
   recompute_basic_faces (f);
 
   do_pending_window_change (0);
diff --git a/src/xdisp.c b/src/xdisp.c
index a793157f086..986e13f43b5 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -13810,6 +13810,7 @@ redisplay_internal (void)
 	      bool gcscrollbars
 		/* Only GC scrollbars when we redisplay the whole frame.  */
 		= f->redisplay || !REDISPLAY_SOME_P ();
+	      bool f_redisplay_flag = f->redisplay;
 	      /* Mark all the scroll bars to be removed; we'll redeem
 		 the ones we want when we redisplay their windows.  */
 	      if (gcscrollbars && FRAME_TERMINAL (f)->condemn_scroll_bars_hook)
@@ -13853,6 +13854,20 @@ redisplay_internal (void)
 			goto retry_frame;
 		    }
 
+		  /* If the frame's redisplay flag was not set before
+		     we went about redisplaying its windows, but it is
+		     set now, that means we employed some redisplay
+		     optimizations inside redisplay_windows, and
+		     bypassed producing some screen lines.  But if
+		     f->redisplay is now set, it might mean the old
+		     faces are no longer valid (e.g., if redisplaying
+		     some window called some Lisp which defined a new
+		     face or redefined an existing face), so trying to
+		     use them in update_frame will segfault.
+		     Therefore, we must redisplay this frame.  */
+		  if (!f_redisplay_flag && f->redisplay)
+		    goto retry_frame;
+
 		  /* Prevent various kinds of signals during display
 		     update.  stdio is not robust about handling
 		     signals, which can cause an apparent I/O error.  */
@@ -13906,8 +13921,10 @@ redisplay_internal (void)
       /* Compare desired and current matrices, perform output.  */
 
     update:
-      /* If fonts changed, display again.  */
-      if (sf->fonts_changed)
+      /* If fonts changed, display again.  Likewise if redisplay_window_1
+	 above caused some change (e.g., a change in faces) that requires
+	 considering the entire frame again.  */
+      if (sf->fonts_changed || sf->redisplay)
 	goto retry;
 
       /* Prevent freeing of realized faces, since desired matrices are