merge revision(s) 9e0a91d0640600f2dfd7fc1d5fae6667019c9ca5: [Backport #18458]

	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 ++-
	 test/ruby/test_exception.rb | 8 ++++++++
	 2 files changed, 10 insertions(+), 1 deletion(-)

1 files changed, 2 insertions, 1 deletions

diff --git a/error.c b/error.c
index 926ec5adb9..a870d0200b 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