Wrap C++ lib with Cython

Question

I'm new to Cython and I'm trying to use Cython to wrap a C/C++ static library. I made a simple example as follow.

Test.h:

#ifndef TEST_H #define TEST_H  int add(int a, int b); int multipy(int a, int b);  #endif 

Test.cpp

#include "test.h" int add(int a, int b) {     return a+b;  }  int multipy(int a, int b) {     return a*b; }  

Then I used g++ to compile and build it.

g++ -c test.cpp -o libtest.o ar rcs libtest.a libtest.o 

So now I got a static library called libtest.a.

Test.pyx:

cdef extern from "test.h":         int add(int a,int b)         int multipy(int a,int b)  print add(2,3) 

Setup.py:

from distutils.core import setup from distutils.extension import Extension from Cython.Distutils import build_ext  ext_modules = [Extension("test",                      ["test.pyx"],                      language='c++',                      include_dirs=[r'.'],                      library_dirs=[r'.'],                      libraries=['libtest']                      )]  setup(   name = 'test',   cmdclass = {'build_ext': build_ext},   ext_modules = ext_modules ) 

The I called:

python setup.py build_ext --compiler=mingw32 --inplace 

The output was:

running build_ext cythoning test.pyx to test.cpp building 'test' extension creating build creating build\temp.win32-2.6 creating build\temp.win32-2.6\Release C:\Program Files\pythonxy\mingw\bin\gcc.exe -mno-cygwin -mdll -O -Wall -I. -IC:\ Python26\include -IC:\Python26\PC -c test.cpp -o build\temp.win32-2.6\Release\test.o writing build\temp.win32-2.6\Release\test.def C:\Program Files\pythonxy\mingw\bin\g++.exe -mno-cygwin -mdll -static --entry _D llMain@12 --output-lib build\temp.win32-2.6\Release\libtest.a --def build\temp.w in32-2.6\Release\test.def -s build\temp.win32-2.6\Release\test.o -L. -LC:\Python 26\libs -LC:\Python26\PCbuild -ltest -lpython26 -lmsvcr90 -o test.pyd g++: build\temp.win32-2.6\Release\libtest.a: No such file or directory error: command 'g++' failed with exit status 1 

I also tried to use libraries=['test'] instead of libraries=['libtest']. It gave me the same errors.

Any clue about this?

Answer 1

If your C++ code is only used by the wrapper, another option is to let the setup compile your .cpp file, like this:

from distutils.core import setup from distutils.extension import Extension from Cython.Distutils import build_ext  ext_modules = [Extension("test",                      ["test.pyx", "test.cpp"],                      language='c++',                      )]  setup(   name = 'test',   cmdclass = {'build_ext': build_ext},   ext_modules = ext_modules ) 

For linking to a static library you have to use the extra_objects argument in your Extension:

from distutils.core import setup from distutils.extension import Extension from Cython.Distutils import build_ext  ext_modules = [Extension("test",                      ["test.pyx"],                      language='c++',                      extra_objects=["libtest.a"],                      )]  setup(   name = 'test',   cmdclass = {'build_ext': build_ext},   ext_modules = ext_modules )