From: Paul Eggert <eggert@cs.ucla.edu>
Date: Mon, 4 Jul 2022 21:21:35 +0000 (-0500)
Subject: Fix core dump with x-get-local-selection
X-Git-Tag: emacs-29.0.90~1447^2~1189
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=6d415d5f0b616fc36f3e5c47a42b6af19eb3d82a;p=emacs.git

Fix core dump with x-get-local-selection

* src/xselect.c (Fx_get_local_selection): Check that VALUE has 4
elements, since x_get_local_selection can dump core otherwise.
This pacifies gcc -Wanalyzer-null-dereference, which found the
problem.
---

diff --git a/src/xselect.c b/src/xselect.c
index 2521dc171c0..1fda300c431 100644
--- a/src/xselect.c
+++ b/src/xselect.c
@@ -2325,9 +2325,13 @@ run.  */)
   Lisp_Object name, timestamp, frame, result;
 
   CHECK_SYMBOL (target);
-  name = Fnth (make_fixnum (0), value);
-  timestamp = Fnth (make_fixnum (2), value);
-  frame = Fnth (make_fixnum (3), value);
+
+  /* Check that VALUE has 4 elements, for x_get_local_selection.  */
+  Lisp_Object v = value; CHECK_CONS (v);
+  name = XCAR (v); v = XCDR (v); CHECK_CONS (v);
+  v = XCDR (v); CHECK_CONS (v);
+  timestamp = XCAR (v); v = XCDR (v); CHECK_CONS (v);
+  frame = XCAR (v);
 
   CHECK_SYMBOL (name);
   CONS_TO_INTEGER (timestamp, Time, time);