setuptools using CC for compiling C++ files

When compiling an extension like

ext_modules = [
    Extension(
        "_foobar",
        [
           # ...
        ],
        language="C++",
    )
]

setuptools appears to use the CC environment variable when compiling the project. E.g.,

CC=clang++ pip3 install . --user --verbose

will switch to clang++. Since this is a C++ project (as specified in the extension), I would have expected CXX to have an effect, and not CC.

[ryandesign]

So is there something that projects need to configure in order to get C++ files compiled with a C++ compiler, or is that simply not possible in setuptools right now, just as it is not possible in distutils? If it’s just not possible, can it please be made possible? (Maybe the patches in the distutils bug report are a starting point?) It is imperative that users (and package management systems acting on their behalf) be able to tell setuptools which C++ compiler to use to compile C++ files and what additional CXXFLAGS to set when doing so.

[pganssle]

Dear @jaraco and @pganssle it seems that no checks are implemented on the language variable (I can set it to language=‘jadshad’ and the installation process would still work). If you point me in the right direction (where to look in the repo), I would be happy to try to tackle this issue. Thank you.

Can you make a separate issue for this, @filippo82? I don’t want the discussion to be lost in the shuffle of this ticket investigation. I think we need to discuss whether it is feasible to be stricter about the specified language and if so what that would look like.