Warn on a finalizer that captures the object to be finalized

Also improve specs and documentation for finalizers and more clearly
recommend a safe code pattern to use them.

1 files changed, 12 insertions, 0 deletions

diff --git a/proc.c b/proc.c
index 3f92ceb365..96c84d20a8 100644
--- a/proc.c
+++ b/proc.c
@@ -2739,6 +2739,18 @@ rb_obj_method_arity(VALUE obj, ID id)
     return rb_mod_method_arity(CLASS_OF(obj), id);
 }
 
+VALUE
+rb_callable_receiver(VALUE callable) {
+    if (rb_obj_is_proc(callable)) {
+        VALUE binding = rb_funcall(callable, rb_intern("binding"), 0);
+        return rb_funcall(binding, rb_intern("receiver"), 0);
+    } else if (rb_obj_is_method(callable)) {
+        return method_receiver(callable);
+    } else {
+        return Qundef;
+    }
+}
+
 const rb_method_definition_t *
 rb_method_def(VALUE method)
 {