Messages in this thread | | | Date | Wed, 2 Feb 2022 12:53:23 -0800 | From | Kees Cook <> | Subject | Re: [PATCH] include: drop pointless __compiler_offsetof indirection |
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On Wed, Feb 02, 2022 at 11:21:47AM +0100, Rasmus Villemoes wrote: > (1) compiler_types.h is unconditionally included via an -include > flag (see scripts/Makefile.lib), and it defines __compiler_offsetof > unconditionally. So testing for definedness of __compiler_offsetof is > mostly pointless. > > (2) Every relevant compiler provides __builtin_offsetof (even sparse > has had that for 14 years), and if for whatever reason one would end > up picking up the poor man's fallback definition (C file compiler with > completely custom CFLAGS?), newer clang versions won't treat the > result as an Integer Constant Expression, so if used in place where > such is required (static initializer or static_assert), one would > get errors like > > t.c:11:16: error: static_assert expression is not an integral constant expression > t.c:11:16: note: cast that performs the conversions of a reinterpret_cast is not allowed in a constant expression > t.c:4:33: note: expanded from macro 'offsetof' > #define offsetof(TYPE, MEMBER) ((size_t)&((TYPE *)0)->MEMBER) > > So just define offsetof unconditionally and directly in terms of > __builtin_offsetof. > > Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Yes please. :)
Reviewed-by: Kees Cook <keescook@chromium.org>
-- Kees Cook
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