[coreboot-gerrit] Change in coreboot[master]: commonlib: Use __builtin_offsetof with supported compilers

[Alex James (Code Review)]

Alex James has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/36249 )

Change subject: commonlib: Use __builtin_offsetof with supported compilers
......................................................................

commonlib: Use __builtin_offsetof with supported compilers

Use __builtin_offsetof (which is treated as a constant expression) with
Clang & GCC. This also allows check_member to work with Clang.

Signed-off-by: Alex James 
Change-Id: I8b5cb4110c13ee42114ecf65932d7f1e5636210e
---
M src/commonlib/include/commonlib/helpers.h
1 file changed, 3 insertions(+), 5 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/49/36249/1

diff --git a/src/commonlib/include/commonlib/helpers.h b/src/commonlib/include/commonlib/helpers.h
index 4429ea4..b5e08b4 100644
--- a/src/commonlib/include/commonlib/helpers.h
+++ b/src/commonlib/include/commonlib/helpers.h
@@ -107,17 +107,15 @@
 #define MHz (1000 * KHz)
 #define GHz (1000 * MHz)

-#ifndef offsetof
+#ifdef __ROMCC__
 #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
+#else
+#define offsetof(TYPE, MEMBER) __builtin_offsetof(TYPE, MEMBER)
 #endif

-#if !defined(__clang__)
 #define check_member(structure, member, offset) _Static_assert( \
    offsetof(struct structure, member) == offset, \
    "`struct " #structure "` offset for `" #member "` is not " #offset)
-#else
-#define check_member(structure, member, offset)
-#endif

/**
  * container_of - cast a member of a structure out to the containing structure