On 5/11/21 5:03 AM, Hyeonggon Yoo wrote: > On Mon, May 10, 2021 at 04:44:09PM +0100, Matthew Wilcox wrote: >> On Tue, May 11, 2021 at 12:02:30AM +0900, Hyeonggon Yoo wrote: >> > @@ -382,8 +385,8 @@ static __always_inline unsigned int kmalloc_index(size_t size) >> > if (size <= 8 * 1024 * 1024) return 23; >> > if (size <= 16 * 1024 * 1024) return 24; >> > if (size <= 32 * 1024 * 1024) return 25; >> > - if (size <= 64 * 1024 * 1024) return 26; >> > - BUG(); >> > + >> > + BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()"); >> >> we're being encouraged to use static_assert() these days. >> https://en.cppreference.com/w/c/language/_Static_assert >> > > can you tell me difference between static_assert and BUILD_BUG_ON? > it seems that mm subsystem does not make use of it now. Some difference is explained in include/linux/build_bug.h near static_assert definition. But importantly it seems it's not possible to place static_assert(false) in place of the BUG() because it will trigger despite not being reachable. BUILD_BUG_ON_MSG(1 "..."); worked as expected for me.
