Replace runtime C++ version detection with compile-time extraction from argv

[anutosh491]

Description

Fixes #348

Type of change

Please tick all options which are relevant.

• Bug fix
• New feature
• Added/removed dependencies
• Required documentation updates

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.81%. Comparing base (6dcf09a) to head (9c8c5c1).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #349      +/-   ##
==========================================
+ Coverage   81.78%   81.81%   +0.02%     
==========================================
  Files          20       20              
  Lines         950      957       +7     
  Branches       87       89       +2     
==========================================
+ Hits          777      783       +6     
- Misses        173      174       +1     

Files with missing lines	Coverage Δ
src/xinterpreter.cpp	89.94% <100.00%> (-0.17%)	⬇️

Files with missing lines	Coverage Δ
src/xinterpreter.cpp	89.94% <100.00%> (-0.17%)	⬇️

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[github-actions]

clang-tidy made some suggestions

[anutosh491]

Thanks for the review !

[vgvassilev]

This is incorrect. Please revert this because that makes sure that we the implementation agrees with the flags.

[JohanMabille]

Hi Vassil, not sure to get it. Does that mean that even if the kernel passes the standard version to use to CppCompiler, this latter might use a different version for any reason? Meaning the resulting standard used is different from the specified one?

[vgvassilev]

Hi Vassil, not sure to get it. Does that mean that even if the kernel passes the standard version to use to CppCompiler, this latter might use a different version for any reason? Meaning the resulting standard used is different from the specified one?

Hi Johan. We can have -std=c++20 but also for some versions of clang -std=c++2a which should be almost the same thing. If you add /std:c++20 style of msvc the matrix becomes pretty hard to manage. Then, we had a but in the option parsing which made it very difficult to debug what the user thought it passed and what the interpreter actually was running with. That is very problematic when debugging ABI issues with libraries which are compiled with one version but you don't really know which version your system is running on.

That's why we implemented this approach where we really ask the interpreter runtime what version of c++ it really has. It's a bit annoying but saves a lot of effort if something slightly goes wrong (as it did in the past).