From 857e384187d8abac2e256f8e97eef3106d982718 Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby-lang.org>
Date: Tue, 4 Feb 2014 14:01:22 +0900
Subject: fibers cannot cross C function boundary; close #1680

---
 mrbgems/mruby-fiber/src/fiber.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/mrbgems/mruby-fiber/src/fiber.c b/mrbgems/mruby-fiber/src/fiber.c
index 757eb235d..43cf76062 100644
--- a/mrbgems/mruby-fiber/src/fiber.c
+++ b/mrbgems/mruby-fiber/src/fiber.c
@@ -218,9 +218,15 @@ static mrb_value
 fiber_yield(mrb_state *mrb, mrb_value self)
 {
   struct mrb_context *c = mrb->c;
+  mrb_callinfo *ci;
   mrb_value *a;
-  int len;
+  int i, len;
 
+  for (ci = c->ci; ci >= c->cibase; ci--) {
+    if (ci->acc < 0) {
+      mrb_raise(mrb, E_ARGUMENT_ERROR, "can't cross C function boundary");
+    }
+  }
   if (!c->prev) {
     mrb_raise(mrb, E_ARGUMENT_ERROR, "can't yield from root fiber");
   }
-- 
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