On Wed, Sep 05, 2018 at 08:48:00AM +0200, Michal Hocko wrote: > Hi Kirill, > while looking at something unrelated I have stumbled over %subj and I > simply do not understand how BUILD_BUG_ON_INVALID is supposed to work > for page flags checks which are dynamic by definition. > BUILD_BUG_ON_INVALID is noop without any side effects unless __CHECKER__ > is enabled when it evaluates to ((void )(sizeof((__force long )(e)))). You've read it backwards. BUILD_BUG_ON_INVALID() is not if __CHECKER__ is enabled. > How is this supposed to work? Am I just confused or BUILD_BUG_ON_INVALID > is simply not a good fit here and all you wanted is the no side-effect > nature of it? Without CONFIG_DEBUG_VM_PGFLAGS() is basically nop. BUILD_BUG_ON_INVALID() here is fance version of nop that check that what you've wrote inside parses fine. That's it. -- Kirill A. Shutemov
