Also can i just check if the founddecl and the decl being used are different - and if so, call diagnoseusedecl on both - or does one have to be a specialization of the other? (do u have an example in mind where it is not a specilaization)
Thanks! Sent from my iPhone On Jun 13, 2013, at 8:03 PM, Faisalv <[email protected]> wrote: > > > Sent from my iPhone > > On Jun 13, 2013, at 7:36 PM, Richard Smith <[email protected]> wrote: > >> On Thu, Jun 13, 2013 at 3:40 PM, Faisalv <[email protected]> wrote: >>> >>> >>> On Jun 13, 2013, at 4:30 PM, Richard Smith <[email protected]> wrote: >>> >>>> Hi Faisal, >>>> >>>> On Thu, Jun 13, 2013 at 11:30 AM, Faisal Vali <[email protected]> wrote: >>>>> While implementing return type deduction for generic lambdas, I stumbled >>>>> upon >>>>> a bug which led to clang mishandling the following code: >>>>> >>>>> struct Lambda { >>>>> template<class T> auto operator()(T t) { >>>>> return 5; >>>>> } >>>>> template<class T> auto foo(T t) { return t; } >>>>> }; >>>>> void test() { >>>>> Lambda L; >>>>> int i = L(3); >>>>> } >>>>> >>>>> >>>>> The issue (as i understand it) was that in some contexts only the >>>>> function template (and not the specialization) would get passed to >>>>> DiagnoseUseOfDecl (which deduces the return type of the function). So >>>>> the specialization would flow through to Codegen with auto as its >>>>> return type. >>>>> >>>>> So, with that in mind, this patch implements a trivial fix. >>>>> >>>>> What do you think Richard? Is there a better way to address this bug? >>>> >>>> I was aware of this issue, but got snowed under with other things. >>>> This bug is not limited to 'auto' type deduction; the other code in >>>> DiagnoseUseOfDecl suffers the same way. For instance: >>>> >>>> struct Lambda { >>>> template<class T> static __attribute__((unused)) int foo(T) { >>>> return 5; >>>> } >>>> }; >>>> int bar() { >>>> Lambda L; >>>> return L.foo(3); >>>> } >>>> >>>> ... does not warn that the function is marked 'unused' but is used, >>>> but if you call it as Lambda::foo(3), it does warn. >>>> >>>> I think the right fix here is to pass both the declaration found by >>>> name lookup and the declaration that is actually used into >>>> DiagnoseUseOfDecl. >>>> >>> >>> What if i just call diagnoseuseofdecl again on the used specialization >>> instead of adding a parameter to it? >> >> If this is the only call which has the problem, then that would be OK. >> I suspect there are other cases, though, and there are probably cases >> which have the opposite bug (passing only the used decl and not the >> found decl). As a quick fix, making two calls would work, but it's >> probably not what we want in the longer term. > > > If its ok w u, for now id rather do the quick fix, place the appropriate > fixmes - and then try and return to this once generic lambdas are starting to > be reasonably usable (plus i still have to figure out that pesky non-odr use, > rvalue emission issue - which also i'm going to deprioritize a lil in favor > of usable generic lambdas for now). Thoughts? _______________________________________________ cfe-commits mailing list [email protected] http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
