aaron.ballman added a comment. In D143524#4150289 <https://reviews.llvm.org/D143524#4150289>, @v.g.vassilev wrote:
> In D143524#4150286 <https://reviews.llvm.org/D143524#4150286>, @aaron.ballman > wrote: > >> In D143524#4148024 <https://reviews.llvm.org/D143524#4148024>, @v.g.vassilev >> wrote: >> >>> Indeed the warning is noisy but it will potentially fix broken code which >>> were unable to diagnose before. Especially that in some cases where static >>> templates in header files are used as an idiom. In theory this approach can >>> extend to cases described in https://wg21.link/p2691 where our inability to >>> diagnose/fix these cases leads to some design decisions which may not be >>> optimal. >> >> We need to ensure the diagnostic is not so noisy that people disable it, >> though. That means a low false positive rate and a straight-forward way to >> silence the diagnostic on a case-by-case basis. > > I agree, so far I have not seen false positives. All issues (except for > `-Wctad-maybe-unsupported` as mentioned above) seemed real. Do you have a > particular example in mind? The concrete example I have is the one under discussion from the test cases, but I was also speaking about the libc++ work that's going on as well. In general, it's best to try the diagnostic on some large-scale C++ projects to see what kind of results you get (compiling projects like LLVM, Qt, Kokkos, Chromium, etc). That usually helps spot other situations like `-Wctad-maybe-unused` etc. ================ Comment at: clang/test/SemaCXX/warn-func-not-needed.cpp:13 namespace test1_template { -template <typename T> static void f() {} +template <typename T> static void f() {} // expected-warning {{unused function template}} template <> void f<int>() {} // expected-warning {{function 'f<int>' is not needed and will not be emitted}} ---------------- v.g.vassilev wrote: > aaron.ballman wrote: > > v.g.vassilev wrote: > > > aaron.ballman wrote: > > > > Why is this unused? `f<long>()` in `foo()` should cause this to be > > > > used, right? > > > > > > > > How should a user silence this diagnostic without disabling it entirely? > > > Nobody uses `foo`. > > Ah, good point on `foo` not being used, but the question still stands -- > > how does the user silence this diagnostic? It's not at all uncommon to have > > a primary template with specializations where the TU only uses either the > > primary or a specialization, but not both (and certainly not all > > specializations). > @philnik used `[[maybe_unused]]` which seemed reasonable to me for silencing > the diagnostic. Maybe take a look at the changes done here: > https://reviews.llvm.org/D144667 That's reasonable if the interface is one the user controls, such as one within a .cpp file. But the situation I'm worried about is where the primary template and specializations live in a header file that's shared between multiple TUs. I don't think it's reasonable to expect users to put `[[maybe_unused]]` on the primary template and all specializations in that situation. Repository: rC Clang CHANGES SINCE LAST ACTION https://reviews.llvm.org/D143524/new/ https://reviews.llvm.org/D143524 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
