Re: [RFC PATCH 1/2] build_bug.h: add wrapper for _Static_assert

[Tom Rini <trini@konsulko.com>]

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On Tue, May 18, 2021 at 11:19:46AM +0200, Rasmus Villemoes wrote:

> [Linux commit 6bab69c65013bed5fce9f101a64a84d0385b3946]
> 
> BUILD_BUG_ON() is a little annoying, since it cannot be used outside
> function scope.  So one cannot put assertions about the sizeof() a
> struct next to the struct definition, but has to hide that in some more
> or less arbitrary function.
> 
> Since gcc 4.6 (which is now also the required minimum), there is support
> for the C11 _Static_assert in all C modes, including gnu89.  So add a
> simple wrapper for that.
> 
> _Static_assert() requires a message argument, which is usually quite
> redundant (and I believe that bug got fixed at least in newer C++
> standards), but we can easily work around that with a little macro
> magic, making it optional.
> 
> For example, adding
> 
>   static_assert(sizeof(struct printf_spec) == 8);
> 
> in vsprintf.c and modifying that struct to violate it, one gets
> 
> ./include/linux/build_bug.h:78:41: error: static assertion failed: "sizeof(struct printf_spec) == 8"
>  #define __static_assert(expr, msg, ...) _Static_assert(expr, "" msg "")
> 
> godbolt.org suggests that _Static_assert() has been support by clang
> since at least 3.0.0.
> 
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
> Reviewed-by: Simon Glass <sjg@chromium.org>

Applied to u-boot/next, thanks!

-- 
Tom

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