How to link C lib against python for embedding under Windows?

Question

Hi,

I am working on an application written in C. One part of the application should embed python and there is my current problem. I try to link my source to the Python library but it does not work.

As I use MinGW I have created the python26.a file from python26.lib with dlltool and put the *.a file in C:/Program Files (x86)/python/2.6/libs.

Therefore, I compile the file with this command:

gcc -shared -o mod_python.dll mod_python.o "-LC:\Program Files (x86)\python\2.6\libs" -lpython26 -Wl,--out-implib,libmod_python.a -Wl,--output-def,mod_python.def

and I get those errors:

Creating library file: libmod_python.a
mod_python.o: In function `module_init':
mod_python.c:34: undefined reference to `__imp__Py_Initialize'
mod_python.c:35: undefined reference to `__imp__PyEval_InitThreads'
... and so on ...

• My Python "root" folder is C:\Program Files (x86)\python\2.6
• The Devsystem is a Windows Server 2008
• GCC Information: Reading specs from C:/Program Files (x86)/MinGW/bin/../lib/gcc/mingw32/3.4.5/specs Configured with: ../gcc-3.4.5-20060117-3/configure --with-gcc --with-gnu-ld --with-gnu-as --host=mingw32 --target=mingw32 --prefix=/mingw --enable-threads --disable-nls --enable-languages=c,c++,f77,ada,objc,java --disable-win32-registry --disable-shared --enable-sjlj-exceptions --enable-libgcj --disable-java-awt --without-x --enable-java-gc=boehm --disable-libgcj-debug --enable-interpreter --enable-hash-synchronization --enable-libstdcxx-debug Thread model: win32 gcc version 3.4.5 (mingw-vista special r3)

What I do wrong? How I get it compiled and linked :-)?

Cheers, gregor

---

Edit: I forgot to write information about my Python installation: It's the official python.org installation 2.6.1

... and how I created the python.a file:

dlltool -z python.def --export-all-symbols -v c:\windows\system32\python26.dll

dlltool --dllname c:\Windows\system32\python26.dll --def python.def -v --output-lib python26.a

Answer 1

Python (at least my distribution) comes with a "python-config" program that automatically creates the correct compiler and linker options for various situations. However, I have never used it on Windows. Perhaps this tool can help you though?

Answer 2

IIRC, dlltool does not always work. Having python 2.6 + Wow makes things even more less likely to work. For numpy, here is how I did it. Basically, I use obdump.exe to build the table from the dll, which I parse to generate the .def. You should check whether your missing symbols are in the .def, or otherwise it won't work.

Answer 3

Well on Windows the python distribution comes already with a libpython26.a in the libs subdir so there is no need to generate .a files using dll tools.

I did try a little example with a single C file toto.c:

$ gcc -shared -o ./toto.dll ./toto.c -I/Python26/include/ -L/Python26/libs -lpython26

And it works like a charm. Hope it will help :-)