From 5c114c91d4ff31859fcd84cf8bf349b737b90d99 Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby-lang.org>
Date: Mon, 10 Apr 2017 09:46:09 +0900
Subject: Clear unused stack region that may refer freed objects; fix #3596

---
 src/gc.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

(limited to 'src')

diff --git a/src/gc.c b/src/gc.c
index 116fd0bfd..19bc1ad4b 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -544,6 +544,7 @@ mark_context_stack(mrb_state *mrb, struct mrb_context *c)
 {
   size_t i;
   size_t e;
+  mrb_value nil;
 
   if (c->stack == NULL) return;
   e = c->stack - c->stbase;
@@ -553,14 +554,14 @@ mark_context_stack(mrb_state *mrb, struct mrb_context *c)
     mrb_value v = c->stbase[i];
 
     if (!mrb_immediate_p(v)) {
-      if (mrb_basic_ptr(v)->tt == MRB_TT_FREE) {
-        c->stbase[i] = mrb_nil_value();
-      }
-      else {
-        mrb_gc_mark(mrb, mrb_basic_ptr(v));
-      }
+      mrb_gc_mark(mrb, mrb_basic_ptr(v));
     }
   }
+  e = c->stend - c->stbase;
+  nil = mrb_nil_value();
+  for (; i<e; i++) {
+    c->stbase[i] = nil;
+  }
 }
 
 static void
-- 
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