From: Eli Zaretskii <eliz@gnu.org>
Date: Mon, 29 Mar 2021 10:39:43 +0000 (+0300)
Subject: Protect add-variable-watcher from incorrect usage
X-Git-Tag: emacs-28.0.90~3102
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=a1e454d6df011f2a02d3b4900dd33d1d3717c6ef;p=emacs.git

Protect add-variable-watcher from incorrect usage

* src/data.c (Fadd_variable_watcher): Avoid crashes if SYMBOL
isn't.  (Bug#47462)
---

diff --git a/src/data.c b/src/data.c
index 0fa491b17a1..3667b03c0e4 100644
--- a/src/data.c
+++ b/src/data.c
@@ -1589,6 +1589,7 @@ All writes to aliases of SYMBOL will call WATCH-FUNCTION too.  */)
   (Lisp_Object symbol, Lisp_Object watch_function)
 {
   symbol = Findirect_variable (symbol);
+  CHECK_SYMBOL (symbol);
   set_symbol_trapped_write (symbol, SYMBOL_TRAPPED_WRITE);
   map_obarray (Vobarray, harmonize_variable_watchers, symbol);