[libcxx-commits] [PATCH] D55840: P0722R3: Implement library support for destroying delete

Tue Feb 12 09:30:35 PST 2019

ldionne added a comment.
Herald added a subscriber: jdoerfert.

In D55840#1382153 <https://reviews.llvm.org/D55840#1382153>, @EricWF wrote:

> Question:
>
> In C++20 we should declare `destroying_delete_t`, even if `__cpp_impl_destroying_delete` isn't defined.
>  But in that case should be define `__cpp_lib_destroying_delete`? The library has the type, but users
>  can't actually perform destroying delete.
>
> Since `__cpp_impl_destroyng_delete` isn't for users, but `__cpp_lib_destroying_delete` is, then I don't think we should define it unless the compiler actually provides the language feature.

I think I agree. We should only define `__cpp_lib_destroying_delete` when the feature can be used sanely. TBH, I don't think that's a question the committee even thought about when introducing feature-test macros? There has to be an expected behaviour for us stdlib implementers here.

Repository:
  rCXX libc++

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https://reviews.llvm.org/D55840