From 8b162ce9d1003e4e469d8f48cb9a2076fd45b47c Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Thu, 1 Aug 2019 20:08:22 +0900
Subject: [PATCH] Fix assertion failure when VM_CHECK_MODE

Some VM frames (dummy and top pushed by `rb_vm_call_cfunc`) has
iseq but has no pc.
---
 gc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gc.c b/gc.c
index fd30c75618..fb8fa53911 100644
--- a/gc.c
+++ b/gc.c
@@ -1926,7 +1926,7 @@ static void
 gc_event_hook_body(rb_execution_context_t *ec, rb_objspace_t *objspace, const rb_event_flag_t event, VALUE data)
 {
     const VALUE *pc = ec->cfp->pc;
-    if (VM_FRAME_RUBYFRAME_P(ec->cfp)) {
+    if (pc && VM_FRAME_RUBYFRAME_P(ec->cfp)) {
         /* increment PC because source line is calculated with PC-1 */
         ec->cfp->pc++;
     }