bug#32038: 27.0.50; Emacs hangs when using :propertize mode line construct and not providing a property value

[Jonathan Kyle Mitchell <kyle@jonathanmitchell.org>]

[-- Attachment #1: Type: text/plain, Size: 404 bytes --]

found 32038 26.1
tags 32038 + patch
quit

I think I found a way to make redisplay ignore any malformed property list by
putting a single check around Fset_text_properties in xdisp.c. The text of the
modeline is still set according to the provided string, but the property list
is ignored if it doesn't have an even number of elements. It doesn't
infinitely loop anymore given a malformed property list.


[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: verify plist before use patch --]
[-- Type: text/x-patch, Size: 1263 bytes --]

From 17eab01494e92e4f9582c56e73ae49278158b016 Mon Sep 17 00:00:00 2001
From: Jonathan Kyle Mitchell <kyle@jonathanmitchell.org>
Date: Tue, 3 Jul 2018 21:44:21 -0500
Subject: [PATCH] Verify plist is a plist before use

Do not blindly use a plist that came from Lisp to set text properties.  This
causes Fset_text_properties to go into an infinite loop during redisplay when
it catches the error in the global error handler (bug#32038).
* src/xdisp.c (display_mode_element):
---
 src/xdisp.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/xdisp.c b/src/xdisp.c
index 9b4febdd61..5f52a5ba6c 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -23610,8 +23610,12 @@ display_mode_element (struct it *it, int depth, int field_width, int precision,
 			= Fdelq (aelt, mode_line_proptrans_alist);
 
 		    elt = Fcopy_sequence (elt);
-		    Fset_text_properties (make_number (0), Flength (elt),
-					  props, elt);
+		    if (EQ (Fmod (Flength (props), make_number (2)),
+			    make_number (0)))
+		      {
+			Fset_text_properties (make_number (0), Flength (elt),
+					      props, elt);
+		      }
 		    /* Add this item to mode_line_proptrans_alist.  */
 		    mode_line_proptrans_alist
 		      = Fcons (Fcons (elt, props),
-- 
2.17.1


[-- Attachment #3: Type: text/plain, Size: 27 bytes --]


--
Jonathan Kyle Mitchell