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 0fa491b17a114bd745664bd944fa6dc108e69725..3667b03c0e41dff762587a739deeb3848de5436c 100644 (file)
--- 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);