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Re: [std-proposals] import std and streams macros

From: SM <hubble.stein_at_[hidden]>
Date: Sun, 3 Mar 2024 15:42:06 +0900
Hello again,

Attached is a draft for introduction of global variables for C streams in
import std;.



On Mon, Feb 19, 2024 at 2:48 AM Arthur O'Dwyer <arthur.j.odwyer_at_[hidden]>

> On Sun, Feb 18, 2024 at 12:38 PM SM via Std-Proposals <
> std-proposals_at_[hidden]> wrote:
>> Hello everyone,
>> I encountered this issue and suggest the following ideas.
>> [...]
>> In C++23, import std was introduced to facilitate the use of standard
>> libraries.
>> However, it does not expose macros, so a user have to include the
>> corresponding header files again, for example:
>> #include <cstdio> // for stderr
>> [...]
>> To resolve other C streams macros, I propose global variables, std::in,
>> std::out, and std::err as substitutes for stdin, stdout, and stderr,
>> respectively.
>> The following papers try to solve the similar macro issues:
>> 1. P2654 Macros And Standard Library Modules - import should suffice
>> <https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2023/p2654r0.pdf>
>> 2. P2884 assert Should Be A Keyword In C++26 - Supporting standard C++23
>> macros in module std
>> <https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2023/p2884r0.pdf>
>> 3. P2883 offsetof Should Be A Keyword In C++26 - Supporting standard
>> C++23 macros in module std
>> <https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2023/p2883r0.pdf>
> Rather than coming up with a different ad-hoc solution for each macro in
> the Standard Library (assert, offsetof, stdin,...), we should be looking
> for a solution that Just Works for all macros. "Just keep using #include"
> is the most obvious solution; but maybe someone can find another. I don't
> think a shotgun approach of ad-hoc solutions is the right way to go, at all.
> (I'd had a vague idea that this was the problem that `import std.compat;`
> was intended to solve; but no, that just puts entities into the global
> namespace in addition to `std`. It doesn't do anything about macros.)
> The same question was asked on StackOverflow last January. No answers yet,
> except for the obvious one of "just keep using #include":
> https://stackoverflow.com/questions/75041883/how-to-use-standard-library-macros-with-std-module-in-c23
> ("Just keep using #include" is not a bad idea, btw. It's certainly what I
> recommend for production codebases, now and for the foreseeable future.)
> my $.02,
> –Arthur

Received on 2024-03-03 06:42:45