From f7624d984bb8c2d879606f1257b317331ad3d7d2 Mon Sep 17 00:00:00 2001
From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Fri, 17 May 2013 02:07:00 +0000
Subject: [PATCH] eval_intern.h: jmpbuf must be accessible

* eval_intern.h (TH_PUSH_TAG): ensure jmpbuf to be accessible before
  pushing tag to get rid of unaccessible tag by stack overflow.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40791 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 ChangeLog     |  5 +++++
 eval_intern.h | 11 +++++++++++
 2 files changed, 16 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index 273ef3b28a..5611194e9f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri May 17 11:06:48 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* eval_intern.h (TH_PUSH_TAG): ensure jmpbuf to be accessible before
+	  pushing tag to get rid of unaccessible tag by stack overflow.
+
 Thu May 16 17:15:32 2013  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* vm_eval.c (rb_catch_obj): add volatile to tag to prevent crash
diff --git a/eval_intern.h b/eval_intern.h
index 190ef9195c..596d45ac82 100644
--- a/eval_intern.h
+++ b/eval_intern.h
@@ -91,9 +91,20 @@ extern int select_large_fdset(int, fd_set *, fd_set *, fd_set *, struct timeval
       rb_fiber_start(); \
   } while (0)
 
+/*
+  ensure tag to be accessible, `buf' is at the beginning.
+  the end is `prev' which is written in TH_PUSH_TAG().
+*/
+#if defined(__GNUC__) && __GNUC__ >= 4
+/* suppress -Wstrict-aliasing, and should be inlined */
+# define ENSURE_TAG_WRITABLE(tag) MEMZERO((tag).buf, int, 1)
+#else
+# define ENSURE_TAG_WRITABLE(tag) (*(volatile int *)(tag).buf = 0)
+#endif
 #define TH_PUSH_TAG(th) do { \
   rb_thread_t * const _th = (th); \
   struct rb_vm_tag _tag; \
+  ENSURE_TAG_WRITABLE(_tag); \
   _tag.tag = 0; \
   _tag.prev = _th->tag; \
   _th->tag = &_tag;