On Thu, Jan 13, 2022 at 09:08:13AM +0100, Rasmus Villemoes wrote:
On 01/11/2021 02.17, Simon Glass wrote:
Some bright sparks have decided that a cast on a constant cannot be a constant, so offsetof() produces this warning on clang-10:
include/intel_gnvs.h:113:1: error: static_assert expression is not an integral constant expression check_member(acpi_global_nvs, unused2, GNVS_CHROMEOS_ACPI_OFFSET); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/linux/kernel.h:284:2: note: expanded from macro 'check_member' offsetof(struct structure, member) == (offset), \ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/linux/stddef.h:20:32: note: expanded from macro 'offsetof' ^ include/intel_gnvs.h:113:1: note: cast that performs the conversions of a reinterpret_cast is ot allowed in a constant expression include/linux/stddef.h:20:33: note: expanded from macro 'offsetof'
Fix it by using the compiler built-in version, if available.
Signed-off-by: Simon Glass sjg@chromium.org
include/linux/stddef.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/include/linux/stddef.h b/include/linux/stddef.h index c540f6100d4..a7f546fdfe5 100644 --- a/include/linux/stddef.h +++ b/include/linux/stddef.h @@ -1,6 +1,8 @@ #ifndef _LINUX_STDDEF_H #define _LINUX_STDDEF_H
+#include <linux/compiler_types.h>
#undef NULL #if defined(__cplusplus) #define NULL 0 @@ -14,7 +16,11 @@
#ifndef __CHECKER__ #undef offsetof -#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER) +#ifdef __compiler_offsetof +#define offsetof(TYPE, MEMBER) __compiler_offsetof(TYPE, MEMBER) +#else +#define offsetof(TYPE, MEMBER) ((size_t)&((TYPE *)0)->MEMBER) +#endif #endif
Can we please just drop the useless indirections? Any compiler we care about provides __builtin_offsetof(), so just make the whole thing
#undef offsetof #define offsetof(TYPE, MEMBER) __builtin_offsetof(TYPE, MEMBER)
And by "compilers we care about", that includes sparse - it has had __builtin_offsetof ever since 2007.
And we can nuke the __compiler_offsetof definition in compiler_types.h, and if any users exist, just mechanically convert them to offsetof().
We should re-sync this with upstream, but that will keep the indirection you're objecting to here, I think.