From 4eddbcf2626b1394e1eb1a9c3928002bb346e178 Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Fri, 11 Aug 2006 07:09:28 +0000
Subject:  r7325@Kushana:  nickm | 2006-08-10 23:37:31 -0700  Use gcc offsetof
 where available.

svn:r7021
---
 src/common/util.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

(limited to 'src/common/util.h')

diff --git a/src/common/util.h b/src/common/util.h
index 7c0cc1c5a..da5d31904 100644
--- a/src/common/util.h
+++ b/src/common/util.h
@@ -91,8 +91,12 @@ extern int dmalloc_free(const char *file, const int line, void *pnt,
 #define tor_memdup(s, n)       _tor_memdup(s, n DMALLOC_ARGS)
 
 /** Return the offset of <b>member</b> within the type <b>tp</b>, in bytes */
-#define STRUCT_OFFSET(tp, member) \
-  ((off_t) (((char*)&((tp*)0)->member)-(char*)0))
+#ifdef __GNUC__
+#define STRUCT_OFFSET(tp, member) __builtin_offsetof(tp, member)
+#else
+ #define STRUCT_OFFSET(tp, member) \
+   ((off_t) (((char*)&((tp*)0)->member)-(char*)0))
+#endif
 
 /* String manipulation */
 #define HEX_CHARACTERS "0123456789ABCDEFabcdef"
-- 
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