Peter Maydell <peter.mayd...@linaro.org> writes: > On Fri, 26 Jun 2020 at 14:57, Paolo Bonzini <pbonz...@redhat.com> wrote: >> >> From: Eric Blake <ebl...@redhat.com> >> >> I'm not aware of any immediate bugs in qemu where a second runtime >> evaluation of the arguments to MIN() or MAX() causes a problem, but >> proactively preventing such abuse is easier than falling prey to an >> unintended case down the road. At any rate, here's the conversation >> that sparked the current patch: >> https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg05718.html > > Hi; the changes in this patch seem to confuse Coverity. > >> +#undef MIN >> +#define MIN(a, b) \ >> + ({ \ >> + typeof(1 ? (a) : (b)) _a = (a), _b = (b); \ >> + _a < _b ? _a : _b; \ >> + }) >> +#define MIN_CONST(a, b) \ >> + __builtin_choose_expr( \ >> + __builtin_constant_p(a) && __builtin_constant_p(b), \ >> + (a) < (b) ? (a) : (b), \ >> + ((void)0)) >> +#undef MAX >> +#define MAX(a, b) \ >> + ({ \ >> + typeof(1 ? (a) : (b)) _a = (a), _b = (b); \ >> + _a > _b ? _a : _b; \ >> + }) >> +#define MAX_CONST(a, b) \ >> + __builtin_choose_expr( \ >> + __builtin_constant_p(a) && __builtin_constant_p(b), \ >> + (a) > (b) ? (a) : (b), \ >> + ((void)0)) > > In particular, where MIN_CONST or MAX_CONST are used to > define values that must be const, eg in qemu-file.c: > 50 DECLARE_BITMAP(may_free, MAX_IOV_SIZE); > or in hcd-xhci.h: > 217 USBPort uports[MAX_CONST(MAXPORTS_2, MAXPORTS_3)]; > > Coverity reports: > > CID 1429992 (#1 of 1): Unrecoverable parse warning (PARSE_ERROR)1. > expr_not_constant: expression must have a constant value > > Can we do something (eg providing fallback less-intelligent > versions of the macro ifdef __COVERITY__) to help it?
Perhaps we can solve the issue with scripts/coverity-model.c. Unfortunately, I can't spare the time to try right now. > (This is the cause of CID 1429992, 1429995, 1429997, > 1429999. Parse errors are unfortunate because Coverity > abandons analysis of the affected function entirely, > and analysis of its callers is also limited.) Bummer. I recommend to revert until we figure out how not to break Coverity.
