[libcxx-commits] [PATCH] D138307: [libc++] Remove default definition of std::char_traits

[Louis Dionne via Phabricator via libcxx-commits]

ldionne added a comment.

In D138307#3946939 <https://reviews.llvm.org/D138307#3946939>, @ldionne wrote:

> In D138307#3946938 <https://reviews.llvm.org/D138307#3946938>, @jyknight wrote:
>
>> This breaks Apache Arrow, which makes a basic_string_view<unsigned long>, here:
>> https://github.com/apache/arrow/blob/91ee6dad722ee154d63eea86ce5644e1e658b53b/cpp/src/arrow/util/bitmap.h#L53
>>
>> [...]
>>
>> Also breaks v8, which uses a std::basic_string<uint16_t> member, https://github.com/v8/v8/blob/0afe3f519821449f00c746df3747543d3458bb68/src/inspector/string-16.h#L113
>
> That is intended, they should fix their usage of `std::string`. If they really want to use `std::string` for these "character types", then they can define `struct MyChar { unsigned long c_; };` and then specialize `std::char_traits<MyChar>`.

One thing we could do is instead deprecate the whole base template (but still provide an implementation) so as to give folks two releases to get off of it. I'm pretty skeptical about `std::string` working as intended for `unsigned long`, but whatever. @tahonermann What would you think about that?


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  https://reviews.llvm.org/D138307/new/

https://reviews.llvm.org/D138307