From 9e0a91d0640600f2dfd7fc1d5fae6667019c9ca5 Mon Sep 17 00:00:00 2001
From: Jeremy Evans <code@jeremyevans.net>
Date: Tue, 4 Jan 2022 09:13:19 -0800
Subject: Don't segfault if Warning.warn is undefined

Check that there is a method entry for the method before passing
it to rb_method_entry_arity.

Fixes [Bug #18458]
---
 error.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'error.c')

diff --git a/error.c b/error.c
index 6a60919d5c..c7c5159927 100644
--- a/error.c
+++ b/error.c
@@ -317,7 +317,8 @@ rb_warning_warn(VALUE mod, VALUE str)
 static int
 rb_warning_warn_arity(void)
 {
-    return rb_method_entry_arity(rb_method_entry(rb_singleton_class(rb_mWarning), id_warn));
+    const rb_method_entry_t *me = rb_method_entry(rb_singleton_class(rb_mWarning), id_warn);
+    return me ? rb_method_entry_arity(me) : 1;
 }
 
 static VALUE
-- 
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