On 01/12/2020 20.56, Nick Desaulniers wrote: > On Tue, Dec 1, 2020 at 9:04 AM Marco Elver <[email protected]> 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
