From: Rich Felker <dalias@aerifal.cx>
Date: Wed, 5 Dec 2012 05:00:42 +0000 (-0500)
Subject: use __builtin_offsetof to implement offsetof when possible
X-Git-Url: http://nsz.repo.hu/git/?p=musl;a=commitdiff_plain;h=a7c1f9727a099da0d4722d4cf81056acd205158b

use __builtin_offsetof to implement offsetof when possible

apparently recent gcc versions have intentionally broken the
traditional definition by treating it as a non-constant expression.
the traditional definition may also be problematic for c++ programs.
---

diff --git a/include/stddef.h b/include/stddef.h
index dbf5a4ae..a5bb9ecc 100644
--- a/include/stddef.h
+++ b/include/stddef.h
@@ -14,6 +14,10 @@
 
 #include <bits/alltypes.h>
 
+#if __GNUC__ > 3
+#define offsetof(type, member) __builtin_offsetof(type, member)
+#else
 #define offsetof(type, member) ((size_t)( (char *)&(((type *)0)->member) - (char *)0 ))
+#endif
 
 #endif