aaron.ballman added reviewers: rsmith, aaron.ballman. aaron.ballman added inline comments.
================ Comment at: clang/test/Parser/objc-static-assert.mm:1 +// RUN: %clang_cc1 -fsyntax-only -verify -Wno-objc-root-class %s + ---------------- erik.pilkington wrote: > thakis wrote: > > aaron.ballman wrote: > > > thakis wrote: > > > > aaron.ballman wrote: > > > > > Can you try explicitly specifying C++98 as the underlying language > > > > > standard mode? I feel like `_Static_assert()` will continue to work > > > > > there (because we made it a language extension in all modes) but > > > > > `static_assert()` may fail (because that's gated on C++11 support). > > > > > If that turns out to be the case, then I think `objc_static_assert` > > > > > should be more complex than expanding to `true`, or we should talk > > > > > about supporting `static_assert()` in all C++ language modes like we > > > > > do for `_Static_assert()`. > > > > Correct, with -std=c++98 static_assert isn't available but > > > > _Static_assert still is. If you want, I can add a test for this, but > > > > this is covered by regular c++ tests already. > > > > > > > > I think the has_feature() should stay as-is though: Else you have no > > > > way to know if _Static_assert works in obj-c mode, and you can check if > > > > static_assert works by checkout has_feature && __cplusplus >= 201103L > > > > if you still care about c++98. > > > > > > > > (And adding one feature each for static_assert and _Static_assert seems > > > > like overkill.) > > > > Correct, with -std=c++98 static_assert isn't available but > > > > _Static_assert still is. If you want, I can add a test for this, but > > > > this is covered by regular c++ tests already. > > > > > > Please do (if we don't change the availability of `static_assert()`), > > > because the test currently relies on the unwritten -std option in order > > > to pass. > > > > > > > I think the has_feature() should stay as-is though: Else you have no > > > > way to know if _Static_assert works in obj-c mode, and you can check if > > > > static_assert works by checkout has_feature && __cplusplus >= 201103L > > > > if you still care about c++98. > > > > > > I don't think this is the correct approach. Testing for `static_assert()` > > > support should not leave the user guessing at what the correct spelling > > > is. > > > > > > > (And adding one feature each for static_assert and _Static_assert seems > > > > like overkill.) > > > > > > Definitely agreed there. > > > > > > I think the correct way forward is to support `static_assert()` in all > > > language modes like we already do for `_Static_assert()`, then > > > `objc_static_assert` becomes useful as-is. I cannot think of a reason why > > > we would want to allow `_Static_assert()` in C++ but not allow > > > `static_assert()`. > > I updated the test. > > > > Accepting `static_assert()` independent of language mode seems pretty > > unrelated to this patch here, so I don't want to do this. > > > > If you don't like the current has_feature approach, I'm all ears for other > > approaches. The current approach allows you to detect if clang can handle > > static_assert in objc objects, and codebases that still care about c++98 > > will have a static_assert wrapping macro keyed off __cplusplus already, so > > that part will transparently just work as well. And codebases that are > > c++11 and newer are in a good position too. I think the current setup is > > pretty good. (But I'm happy to hear better suggestions.) > > Accepting static_assert() independent of language mode seems pretty > > unrelated to this patch here, so I don't want to do this. > > Yeah, we shouldn't be treating `static_assert` as a keyword in C++98 or C, I > think. It would break code. > > > If you don't like the current has_feature approach, I'm all ears for other > > approaches. The current approach allows you to detect if clang can handle > > static_assert in objc objects, and codebases that still care about c++98 > > will have a static_assert wrapping macro keyed off __cplusplus already, so > > that part will transparently just work as well. And codebases that are > > c++11 and newer are in a good position too. I think the current setup is > > pretty good. (But I'm happy to hear better suggestions.) > > This is pretty weird. This feature flag doesn't actually correspond to any > feature, just the possibility of the existence of a feature (there isn't any > way you could use this `__has_feature` portably without also including > another `__has_feature` check). I think the most internally consistent way of > doing this is to have two flags, as you mentioned above, > `objc_c_static_assert` and `objc_cxx_static_assert`. > > Just to keep the bikeshed going, maybe it should be spelt > `objc_interface_c_static_assert` or something, to show that it doesn't > control static_assert in ObjC, but static_assert in interfaces in ObjC. > Yeah, we shouldn't be treating static_assert as a keyword in C++98 or C, I > think. It would break code. That depends on how we implemented the feature (we could parse the token as an identifier and check the spelling in situations where static_assert() can grammatically appear, for instance). I do have a hunch that this should be possible to support, though it's nontrivial and I don't expect @thakis to do it as part of this feature. > I think the most internally consistent way of doing this is to have two > flags, as you mentioned above, objc_c_static_assert and > objc_cxx_static_assert. Yeah, as much as I didn't like the idea at first blush, I'm starting to think it's the best way forward. I don't want to ever explain why `__has_feature(objc_static_assert)` return true with `-std=c++98` and yet `static_assert(true, "");` fails to compile while `_Static_assert(true, "")` succeeds. That's inexplicable behavior, IMO. Having two feature test macros alleviates that concern. > Just to keep the bikeshed going, maybe it should be spelt > objc_interface_c_static_assert or something, to show that it doesn't control > static_assert in ObjC, but static_assert in interfaces in ObjC. That seems reasonable to me. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D59223/new/ https://reviews.llvm.org/D59223 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
