commit 928fbfa8b71b7486ea1a53d59bcd5c42887d5f7b
author Olivier Houchard <ohouchard@haproxy.com> Wed Jan 24 18:17:06 2018 +0100
committer Willy Tarreau <w@1wt.eu> Mon Feb 05 14:24:50 2018 +0100
tree b52863216e6324ba1f00cc288d4223db73d5b9dd
parent 25ae45a078f1b2efca7931d6cf6392aa5a0a9775

MINOR: compiler: introduce offsetoff().

Add a offsetof() macro, if it is no there already.

include/common/compiler.h

diff --git a/include/common/compiler.h b/include/common/compiler.h
index a13aad5..125c473 100644
--- a/include/common/compiler.h
+++ b/include/common/compiler.h
@@ -107,5 +107,23 @@
 #endif
 #endif
 
+#ifndef __GNUC_PREREQ__
+#if defined(__GNUC__) && !defined(__INTEL_COMPILER)
+#define __GNUC_PREREQ__(ma, mi) \
+        (__GNUC__ > (ma) || __GNUC__ == (ma) && __GNUC_MINOR__ >= (mi))
+#else
+#define __GNUC_PREREQ__(ma, mi) 0
+#endif
+#endif
+
+#ifndef offsetof
+#if __GNUC_PREREQ__(4, 1)
+#define offsetof(type, field)  __builtin_offsetof(type, field)
+#else
+#define offsetof(type, field) \
+        ((__size_t)(__uintptr_t)((const volatile void *)&((type *)0)->field))
+#endif
+#endif
+
 
 #endif /* _COMMON_COMPILER_H */