aaron.ballman added inline comments.
================ Comment at: lib/Sema/SemaDeclAttr.cpp:2054 - } - // If this is spelled as the standard C++17 attribute, but not in C++17, warn ---------------- Quuxplusone wrote: > @aaron.ballman writes: > > I don't think we're currently diagnosing static data members of classes as > > being unused in the first place; are there plans to implement that > > functionality so that someone might want to write the attribute there? > > FWIW, "plans to implement that functionality" (in Clang) is not the only > reason to accept the attribute. Someone might write the attribute in their > codebase that currently compiles with some //other// compiler which > implements the functionality (or at least does not reject it); it would be > mildly unfortunate if that made their codebase non-portable-to-Clang. (Only > "mildly" because the diagnostic being removed here is just a warning; the > user could suppress it if they really needed to.) > > Here's an example of code that compiles cleanly with GCC but gives an > arguably "false positive" diagnostic when compiled with Clang. > https://wandbox.org/permlink/UG4kG5XTBn12xfuu > Now, admittedly, both GCC and Clang produce a "false negative" re the unused > private static member `y`; but that false negative might get fixed in the > future. The user writes their code //today// and it must compile //today//. :) > Agreed; that's why the analysis isn't a requirement for accepting this patch. I was mostly just curious if there were plans to extend that functionality or not. ================ Comment at: test/CXX/dcl.dcl/dcl.attr/dcl.attr.unused/p2.cpp:5 int I [[maybe_unused]]; - static int SI [[maybe_unused]]; // expected-warning {{'maybe_unused' attribute only applies to variables, functions, methods, types, enumerations, enumerators, labels, and non-static data members}} + static int SI [[maybe_unused]]; }; ---------------- Quuxplusone wrote: > aaron.ballman wrote: > > cpplearner wrote: > > > lebedev.ri wrote: > > > > As the code comment noted, > > > > http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/n4659.pdf, page > > > > 199: > > > > ``` > > > > 2 The attribute may be applied to the declaration of a class, a > > > > typedef-name, a variable, a **non-static** data > > > > member, a function, an enumeration, or an enumerator. > > > > ``` > > > That section says that [[maybe_unused]] can be applied to a non-static > > > data member, which doesn't mean it can't be applied to a static data > > > member. > > > > > > And I'm arguing that since a static data member is a variable, > > > [dcl.attr.unused]p2 actually allows [[maybe_unused]] to be applied to a > > > static data member. > > Yes -- through twisty standardese, a static data member of a class might be > > a variable. This test case, however, is only a declaration and not a > > definition (which means it's not an object, which means it's not a > > variable). Should the attribute still appertain in this case? > The attribute does currently apply to declarations as well as definitions, > although you have to be a real language lawyer to observe it. > https://wandbox.org/permlink/WBLWBdd42rv95UaS Good point. Also, declaration vs definition doesn't really matter when I think about it -- the whole point is to tell you "hey, this is unused" and give the programmer a way to say "maybbbbbe it's unused, but shut up about it anyway." Definition vs declaration doesn't much matter in that case. Repository: rC Clang https://reviews.llvm.org/D45403 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
