Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: David Brown <david.brown@hesbynett.no>
Newsgroups: comp.lang.c++
Subject: Re: We have a new standard!
Date: Thu, 2 Jan 2025 17:57:06 +0100
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On 02/01/2025 16:35, Michael S wrote:
> On Thu, 2 Jan 2025 13:51:53 +0100
> David Brown <david.brown@hesbynett.no> wrote:
> 
>>
>> Could this all have been done from the start of C++?  In theory, yes
>> - in practice no.  std::format and std::print rely on various modern
>> C++ features, such as compile-time evaluation of functions,
> 
> It does not look like dependence of std::format on compile-time
> evaluation is a requirement of standard rather than implementation
> choice of g++ and of clang++.
> 
> MSVC 19.30.30706 compiles the following code just fine:
> 
> #include <cstdio>
> #include <format>
> 
> int main(int argc, char** argv)
> {
>    if (argc >= 3) {
>      std::string s = std::format(argv[1], argv[2]);
>      printf("%s\n", s.c_str());
>    }
>    return 0;
> }
> 
> When run, it produces expected results.
> 
> Or, may be, it's because this version of MSVC is not fully C++20
> complient.
> 

<https://en.cppreference.com/w/cpp/utility/format/format>

Apparently P2216R3 made compile-time checks for std::format a 
requirement.  I don't know where that fits with standard versions, or 
compiler support.  I am just going by what it says in the reference here.