From a7b0ab3769d9f7f13d47c2c6f23298c87b88eee8 Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby-lang.org>
Date: Wed, 5 Apr 2017 22:28:46 +0900
Subject: Save block argument position in e->cioff; fix #3593

---
 src/kernel.c | 10 ++++++++--
 src/vm.c     |  5 +++++
 2 files changed, 13 insertions(+), 2 deletions(-)

(limited to 'src')

diff --git a/src/kernel.c b/src/kernel.c
index 8670e0651..5ac0a3774 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -157,8 +157,14 @@ mrb_f_block_given_p_m(mrb_state *mrb, mrb_value self)
         /* top-level does not have block slot (alway false) */
         if (sp == mrb->c->stbase)
           return mrb_false_value();
-        ci = mrb->c->cibase + e->cioff;
-        bp = ci[1].stackent + 1;
+        if (e->cioff < 0) {
+          /* use saved block arg position */
+          bp = &e->stack[-e->cioff];
+        }
+        else {
+          ci = mrb->c->cibase + e->cioff;
+          bp = ci[1].stackent + 1;
+        }
       }
     }
     if (ci->argc > 0) {
diff --git a/src/vm.c b/src/vm.c
index 518323cf7..f67e73533 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -257,8 +257,13 @@ mrb_env_unshare(mrb_state *mrb, struct REnv *e)
 {
   size_t len = (size_t)MRB_ENV_STACK_LEN(e);
   mrb_value *p = (mrb_value *)mrb_malloc(mrb, sizeof(mrb_value)*len);
+  ptrdiff_t cioff = e->cioff;
 
   MRB_ENV_UNSHARE_STACK(e);
+  if (!e->c) {
+    /* save block argument position (negated) */
+    e->cioff = -mrb->c->cibase[cioff].argc-1;
+  }
   if (len > 0) {
     stack_copy(p, e->stack, len);
   }
-- 
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