[libcxx-commits] [libcxx] [libcxx][c++26] 2937R0: Freestanding: Remove strtok (PR #146290)

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dywoq wrote:

> > > I don't think this is the right approach here. `_LIBCPP_USING_IF_EXISTS` is there to make `std::strtok` available exactly when `::strtok` is available, which seems like a _much_ more useful way of handling this than arbitrarily disabling it because `-ffreestanding` was set. Generally, I don't think we should check for `-ffreestanding` directly in the headers at any point.
> > 
> > 
> > `__STDC_HOSTED__ == 1 || _LIBCPP_STD_VER < 26` is the thing what [P2937R0](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2023/p2937r0.html) requires. Since `<cstring>` is a freestanding header (not completely),
> 
> This is incorrect. We're simply not required to provide `strtok`. We are allowed to do that though.
> 
> > ```c++
> > using ::strtok _LIBCPP_USING_IF_EXIST;
> > ```
> > 
> > 
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> > must be removed from `<cstring>` in C++26, using macro condition:
> > ```c++
> > #if __STDC_HOSTED__ == 1 || _LIBCPP_STD_VER < 26
> > using ::strtok _LIBCPP_USING_IF_EXISTS;
> > #endif
> > ```
> > 
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> > Different C libraries might have different interpretations of what should be freestanding.
> 
> Which is exactly why we have `_LIBCPP_USING_IF_EXISTS`. If it's available in the global namespace, we import it into `std`. Otherwise we don't. That's what the attribute does.

Okay, if you're sure, I'll remove the condition.


https://github.com/llvm/llvm-project/pull/146290