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 <s...@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(). Rasmus
