From ab99e2c293167935033016750c010047a2aba76a Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby-lang.org>
Date: Fri, 1 Sep 2017 06:50:24 +0900
Subject: Avoid copying over initialized procs using `initialize_copy`; fix
 #3803

It may be better to raise exceptions, but CRuby doesn't.
---
 src/proc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/proc.c b/src/proc.c
index 96b080f9e..10a2c4f33 100644
--- a/src/proc.c
+++ b/src/proc.c
@@ -139,6 +139,10 @@ mrb_proc_cfunc_env_get(mrb_state *mrb, mrb_int idx)
 void
 mrb_proc_copy(struct RProc *a, struct RProc *b)
 {
+  if (a->body.irep) {
+    /* already initialized proc */
+    return;
+  }
   a->flags = b->flags;
   a->body = b->body;
   if (!MRB_PROC_CFUNC_P(a) && a->body.irep) {
-- 
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