From 8271863fe5abb6d706d25f1dec87160f91bb28ff Mon Sep 17 00:00:00 2001
From: Yukihiro Matsumoto <matz@ruby-lang.org>
Date: Tue, 16 Oct 2012 23:46:34 +0900
Subject: Kernel#block_given? always gave false

---
 src/kernel.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/kernel.c b/src/kernel.c
index cf3ee2344..43820173c 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -235,6 +235,12 @@ mrb_f_block_given_p_m(mrb_state *mrb, mrb_value self)
   bp = mrb->stbase + ci->stackidx + 1;
   ci--;
   if (ci <= mrb->cibase) return mrb_false_value();
+  /* block_given? called within block; check upper scope */
+  if (ci->proc->env && ci->proc->env->stack) {
+    if (ci->proc->env->stack == mrb->stbase || mrb_nil_p(ci->proc->env->stack[1]))
+      return mrb_false_value();
+    return mrb_true_value();
+  }
   if (ci->argc > 0) {
     bp += ci->argc;
   }
-- 
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