python – How to tell distutils to use gcc?-ThrowExceptions

Exception or error:

I want to wrap a test project containing C++ and OpenMP code with Cython, and build it with distutils via a file. The content of my file looks like this:

from distutils.core import setup
from distutils.extension import Extension
from Cython.Build import cythonize
from Cython.Distutils import build_ext

modules = [Extension("Interface",
                     ["Interface.pyx", "Parallel.cpp"],
                     language = "c++",

for e in modules:
    e.cython_directives = {"embedsignature" : True}

     cmdclass={"build_ext": build_ext},

The -fopenmp flag is used with gcc to compile and link against OpenMP. However, if I just invoke

cls ~/workspace/CythonOpenMP/src $ python3 build

this flag is not recognized, because the compiler is clang:

running build
running build_ext
skipping 'Interface.cpp' Cython extension (up-to-date)
building 'Interface' extension
cc -Wno-unused-result -fno-common -dynamic -DNDEBUG -g -O3 -Wall -Wstrict-prototypes -I/usr/local/include -I/usr/local/opt/sqlite/include -I/usr/local/Cellar/python3/3.3.0/Frameworks/Python.framework/Versions/3.3/include/python3.3m -c Interface.cpp -o build/temp.macosx-10.8-x86_64-3.3/Interface.o -fopenmp
clang: warning: argument unused during compilation: '-fopenmp'
cc -Wno-unused-result -fno-common -dynamic -DNDEBUG -g -O3 -Wall -Wstrict-prototypes -I/usr/local/include -I/usr/local/opt/sqlite/include -I/usr/local/Cellar/python3/3.3.0/Frameworks/Python.framework/Versions/3.3/include/python3.3m -c Parallel.cpp -o build/temp.macosx-10.8-x86_64-3.3/Parallel.o -fopenmp
clang: warning: argument unused during compilation: '-fopenmp'
Parallel.cpp:24:10: warning: unknown pragma ignored [-Wunknown-pragmas]
        #pragma omp parallel for
1 warning generated.
c++ -bundle -undefined dynamic_lookup -L/usr/local/lib -L/usr/local/opt/sqlite/lib build/temp.macosx-10.8-x86_64-3.3/Interface.o build/temp.macosx-10.8-x86_64-3.3/Parallel.o -o build/lib.macosx-10.8-x86_64-3.3/ -fopenmp
ld: library not found for -lgomp
clang: error: linker command failed with exit code 1 (use -v to see invocation)
error: command 'c++' failed with exit status 1

I’ve unsucessfully tried to specify gcc:

cls ~/workspace/CythonOpenMP/src $ python3 build --compiler=g++-4.7
running build
running build_ext
error: don't know how to compile C/C++ code on platform 'posix' with 'g++-4.7' compiler

How can I tell distutils to use gcc?

How to solve:

Try setting the “CC” environment variable from inside the with os.environ.


Just in case some others are facing the same problem under Windows (where CC environment variable wouldn’t have any effect) :

  • Create file “C:\Python27\Lib\distutils\distutils.cfg” and write this inside :

Code :

compiler = mingw32
  • Remove all instances of “-mno-cygwin” gcc option from file “C:\Python27\Lib\distutils\” :

This :

    self.set_executables(compiler='gcc -mno-cygwin -O -Wall',
                         compiler_so='gcc -mno-cygwin -mdll -O -Wall',
                         compiler_cxx='g++ -mno-cygwin -O -Wall',
                         linker_exe='gcc -mno-cygwin',
                         linker_so='%s -mno-cygwin %s %s'
                                    % (self.linker_dll, shared_option,

Becomes this :

self.set_executables(compiler='gcc -O -Wall',
                     compiler_so='gcc -mdll -O -Wall',
                     compiler_cxx='g++ -O -Wall',
                     linker_so='%s %s %s'
                                % (self.linker_dll, shared_option,

The second point can be necessary in case you are using a recent version of gcc, where the deprecated option -mno-cygwin has been removed.

Hope this will help even if it is not directly related to the OP real needs (but still related to the question’s title…)


I just took a look at the distutils source, and the --compiler option expects “unix”, “msvc”, “cygwin”, “mingw32”, “bcpp”, or “emx”. It checks the compiler name you want by checking the CC environment variable. Try calling build like this:

CC=gcc python build

You don’t need to set CXX, it doesn’t check for that.


According to this wiki, Python versions after 3.4 do not support MinGW anymore.
CPython 3.7 for Windows is compiled with MSC v.1916. When I try to use above-mentioned method with distutils.cfg, I then get an error from distutils: Unknown MS Compiler Version 1916. Looks like it has a hardcoded table of msvcr libraries in its file (which is also responsible for MinGW), and last version known to that file is 1600 from VS2010 / MSVC 10.0.


Try this:

In short, it appears that you should try: python build –compiler=g++ first.

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