How to identify compiler before defining cython extensions?

Question

I'm building a platform independent cython project where I want to pass compiler args based on the compiler being used. I can guess the compiler based on platform or assume it's the same compiler used for Python but it's not guaranteed to match. Normally I inject into the cmdclass arg to setuptool's setup method and wrap the install or build_ext commands to check internal state. But in this case I have to cythonize the extension modules before I reach the wrappers.

Is there any way to determine the compiler inside setup.py before cythonizing the extension modules?

Answer 1

After posting on the cython forums and searching for related issues in distutils I found this post showing how to move the compiler arguments into the build_ext assignment. If I subsequently remove all compiler arguments from the extension class I can now lazy assign them inside the command class as I expected. I can also get install and egg_info command classes to call my new version of the build_ext as well.

from setuptools.command.build_ext import build_ext

BUILD_ARGS = defaultdict(lambda: ['-O3', '-g0'])
for compiler, args in [
        ('msvc', ['/EHsc', '/DHUNSPELL_STATIC']),
        ('gcc', ['-O3', '-g0'])]:
    BUILD_ARGS[compiler] = args
    
class build_ext_compiler_check(build_ext):
    def build_extensions(self):
        compiler = self.compiler.compiler_type
        args = BUILD_ARGS[compiler]
        for ext in self.extensions:
            ext.extra_compile_args = args
        build_ext.build_extensions(self)

...
setup(
    ...
    cmdclass={ 'build_ext': build_ext_compiler_check })

Answer 2

A simple variation of the first answer:

from setuptools import setup, Extension
from distutils.command.build_ext import build_ext

myextension = Extension(
    name = 'packagename',
    sources = [
        'source/debugger.cpp',
    ],
    include_dirs = [ 'source' ],
)

class build_ext_compiler_check(build_ext):
    def build_extensions(self):
        compiler = self.compiler.compiler_type

        # print('\n\ncompiler', compiler)
        if not 'msvc' in compiler:

            for extension in self.extensions:

                if extension == myextension:
                    extension.extra_compile_args.append( '-O0' )
                    extension.extra_compile_args.append( '-std=c++11' )

        super().build_extensions()

setup(
        name = 'packagename',
        version = __version__,
        ext_modules= [ myextension ],
    )