Quoting Peter Maydell (2015-07-21 06:42:41) > On 5 June 2015 at 16:20, Paolo Bonzini <pbonz...@redhat.com> wrote: > > On 05/06/2015 17:08, Peter Maydell wrote: > >>> > Can someone add a checkpatch rule that forbids shifting left U or UL > >>> > constants (i.e. only ULL)? That would alleviate my concerns with these > >>> > ubsan warnings. > >> > >> ...but things like "(1U << 31)" are entirely valid. > > > > They're only valid until someone does a ~ on them. I think it's > > reasonable to forbid them in our coding standards, if we want to fix > > ubsan's warning of (1 << 31). > > > > I don't think it's reasonable for compiler writers to exploit the > > undefinedness of (1 << 31) anyway, and if it were possible to shut up > > ubsan about this particular kind of undefined behavior, I would prefer it. > > I just checked, and it isn't possible to suppress this particular > shift warning without also turning off others that we would want > to retain. > > The ppc code is still provoking this sanitizer warning in my > test runs :-(
Was I being silly by not just doing this is the first place? -#define DRC_INDEX_ID_MASK (~(~0 << DRC_INDEX_TYPE_SHIFT)) +#define DRC_INDEX_ID_MASK ((1 << DRC_INDEX_TYPE_SHIFT) - 1) Will send a proper patch to list in a moment. > > thanks > -- PMM >
