build: Remove usage of deprecated std::aligned_storage/union #9297
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Author victorvianna not on autobuild list. Waiting for curator authorization before starting CI build. |
| @@ -174,7 +133,7 @@ using is_invocable_r = is_invocable_r_impl<void, R, F, Args...>; | |||
| } // namespace inplace_function_detail | |||
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| template <class Signature, size_t Capacity = inplace_function_detail::InplaceFunctionDefaultCapacity, | |||
| size_t Alignment = alignof(inplace_function_detail::aligned_storage_t<Capacity>)> | |||
| size_t Alignment = alignof(std::max_align_t)> | |||
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Alignment will now always be the strictest, it can be improved it seems by replacing usage of aligned_storage with something similar to what is described here: https://stackoverflow.com/questions/71828288/why-is-stdaligned-storage-to-be-deprecated-in-c23-and-what-to-use-instead
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Thanks! Have you checked the godbolt link I added to the PR description? Alignment does not appear to increase in practice.
Also, IIUC the snippets you link use an explicit alignment parameter (i.e. aligned_storage<X, Y> not aligned_storage<X>), so they don't apply here. Even in the official guidance from the c++ committee there's no suggested replacement for aligned_storage<X> (see "Suggested replacement" section).
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p1413r3.pdf
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Thank you for those details! With your change though, in practice there is a difference. See this: https://godbolt.org/z/hjGc8dqM9
Just switch which inplace_function.h gets included at the top, from the current one to your updated one. Alignment increases with this update : /
These are deprecated in c++23. Note: in the one instance where the default Align value was used for std::aligned_storage<Len, Alignment> (i.e. std::aligned_storage<Len>), this patch now adopts alignof(std::max_align_t). According to [1] that should be a behavior change, but in practice it doesn't seem to be when using clang nor gcc. In any case, any change in the alignment would be an increase, which is fine. [1] https://en.cppreference.com/w/cpp/types/aligned_storage [2] https://godbolt.org/z/K5xGcxhjh
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Author victorvianna not on autobuild list. Waiting for curator authorization before starting CI build. |
These are deprecated in c++23.
Note: in the one instance where the default Align value was used for std::aligned_storage<Len, Alignment> (i.e.
std::aligned_storage), this patch now adopts
alignof(std::max_align_t). According to [1] that should be a behavior change, but in practice it doesn't seem to be when using clang nor gcc [2]. In any case, any change in the alignment would be an increase, which is fine.
[1] https://en.cppreference.com/w/cpp/types/aligned_storage
[2] https://godbolt.org/z/K5xGcxhjh