enforce the compiler requirement in header

[JeffGarland]

The compiler requirement enforcement should be done like this example. It can also be done in cmake, but I prefer this approach in case someone pulls headers without the cmake.

https://github.com/bemanproject/scope/blob/main/include/beman/scope/scope.hpp#L12-L15

[ashu3103]

Hi @JeffGarland,

I'm self-assigning this issue, I hope I'm not violating any community rules

[JeffGarland]

No rule violations at all -- you're the primary author here so please take issues and resolve them at will! w.r.t best practices I recommend creating a branch with the issue number in the primary repo to do the work. Then when you issue a PR it will automatically close the issue and the relationship will be clear. Note some like to fork the repo into their own, but you have write access here so that seems like unecessary overhead.

w.r.t. policy if you haven't already look over the guidance docs https://bemanproject.org/docs/ -- and please feel free to ask questions on either the discord or discourse.

[ashu3103]

Alright, Thanks!

[ashu3103]

Hi @JeffGarland,

We wish to restrict users to c++23 and therefore I'm applying the condition:
#if __cplusplus < 202302L

But something unexpected is happening, I'm getting #define __cplusplus 202100L instead (output of command: g++ -dM -E -x c++ /dev/null | grep -F __cplusplus and my gcc version is 13.3.0 btw), however their official docs says:

__cplusplus

This macro is defined when the C++ compiler is in use. You can use __cplusplus to test whether a header is 
compiled by a C compiler or a C++ compiler. This macro is similar to __STDC_VERSION__, in that it expands to a 
version number. Depending on the language standard selected, the value of the macro is 199711L for the 1998 C++ 
standard, 201103L for the 2011 C++ standard, 201402L for the 2014 C++ standard, 201703L for the 2017 C++ 
standard, 202002L for the 2020 C++ standard, 202302L for the 2023 C++ standard, or an unspecified value strictly 
larger than 202302L for the experimental languages enabled by -std=c++26 and -std=gnu++26.

I was thinking of the following alternatives:

• make the check less strict: #if __cplusplus < 202100L
• enforce higher gcc versions like 14+ (because some on the internet claim gcc < 14 doesn't properly support C++23)
• use feature flags instead of __cplusplus directive like (check presence of __cpp_lib_ranges)

What do you suggest?

[ashu3103]

Also, do we (The Beman project) have a tool that can test the library with different compilers and versions options (like gcc/clang/MSVC etc) under sandbox environment (which we can even integrate in README)?