Re: [PATCH] genksyms: Ignore module scoped _Static_assert()

[Rasmus Villemoes]

On 01/12/2020 20.56, Nick Desaulniers wrote:
> On Tue, Dec 1, 2020 at 9:04 AM Marco Elver <elver@xxxxxxxxxx> wrote:
>>
>> On Tue, Dec 01, 2020 at 04:14PM +0000, Christoph Hellwig wrote:
>>> Why not use the kernels own BUILD_BUG_ON instead of this idiom?
>>
> And to proactively address the inevitable: why do we have both?  We
> looked into wholesale replacing BUILD_BUG_ON's implementation with
> _Static_assert, but found that they differ slightly in the handling of
> integer constant expressions; BUILD_BUG_ON was reliant on some
> compiler optimizations in expressions making use of
> __builtin_constant_p that cannot be evaluated when the compiler
> performs the _Static_assert check. 

... and _Static_assert() is a declaration, so even many of the
BUILD_BUG_ON() that have a bona fide ICE cannot be converted because
declaration-after-statement.

Rasmus