From: Eli Zaretskii <eliz@gnu.org>
Date: Sat, 23 Dec 2017 11:59:07 +0000 (+0200)
Subject: Avoid crashes when ':eval' deletes our frame
X-Git-Tag: emacs-26.0.91~76
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=720ed0b5334c9667b2fdc4d3f5e8975865e9f962;p=emacs.git

Avoid crashes when ':eval' deletes our frame

* src/xdisp.c (display_mode_element): Signal an error if
':eval' somehow deletes the frame whose window we are
redisplaying. (Bug#29726)
---

diff --git a/src/xdisp.c b/src/xdisp.c
index 538c3e6b87e..f6e98daa329 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -23685,6 +23685,14 @@ display_mode_element (struct it *it, int depth, int field_width, int precision,
 	      {
 		Lisp_Object spec;
 		spec = safe__eval (true, XCAR (XCDR (elt)));
+		/* The :eval form could delete the frame stored in the
+		   iterator, which will cause a crash if we try to
+		   access faces and other fields (e.g., FRAME_KBOARD)
+		   on that frame.  This is a nonsensical thing to do,
+		   and signaling an error from redisplay might be
+		   dangerous, but we cannot continue with an invalid frame.  */
+		if (!FRAME_LIVE_P (it->f))
+		  signal_error (":eval deleted the frame being displayed", elt);
 		n += display_mode_element (it, depth, field_width - n,
 					   precision - n, spec, props,
 					   risky);