From bb8abf62d3cb783b6b8ffeffb67c5ff519332c20 Mon Sep 17 00:00:00 2001
From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Tue, 14 Jul 2015 23:59:23 +0000
Subject: gc.h: evaluate the macro argument only once

* gc.h (RUBY_MARK_UNLESS_NULL): evaluate the argument only once
  to get rid of inadvertent side effects.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51247 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 gc.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

(limited to 'gc.h')

diff --git a/gc.h b/gc.h
index 19c712b44d..d1021df444 100644
--- a/gc.h
+++ b/gc.h
@@ -57,7 +57,10 @@ rb_gc_debug_body(const char *mode, const char *msg, int st, void *ptr)
 #define RUBY_GC_INFO if(0)printf
 #endif
 
-#define RUBY_MARK_UNLESS_NULL(ptr) if(RTEST(ptr)){rb_gc_mark(ptr);}
+#define RUBY_MARK_UNLESS_NULL(ptr) do { \
+    VALUE markobj = (ptr); \
+    if (RTEST(markobj)) {rb_gc_mark(markobj);} \
+} while (0)
 #define RUBY_FREE_UNLESS_NULL(ptr) if(ptr){ruby_xfree(ptr);(ptr)=NULL;}
 
 #if STACK_GROW_DIRECTION > 0
-- 
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