Embedding Python in C, linking fails with undefined reference to `Py_Initialize'

Miguellissimo picture Miguellissimo · Dec 28, 2014 · Viewed 16.8k times · Source

I am trying to compile the example from the docs https://docs.python.org/2.7/extending/embedding.html and my code looks exactly like the one under 5.1:

#include <Python.h>

int
main(int argc, char *argv[])
{
  Py_SetProgramName(argv[0]);
  Py_Initialize();
  PyRun_SimpleString("from time import time, ctime\n"
                     "print 'Today is', ctime(time())\n");

  Py_Finalize();
  return 0;
}

I use the following command to compile it which works fine for me and gives me the desired object file:

gcc -c $(python2.7-config --cflags) embedpy.c

To link it I use the following command which ends up in the following error:

gcc $(/usr/bin/python2.7-config --ldflags) embedpy.o
embedpy.o: In function `main':
/home/miguellissimo/embedpy.c:6: undefined reference to `Py_SetProgramName'
/home/miguellissimo/embedpy.c:7: undefined reference to `Py_Initialize'
/home/miguellissimo/embedpy.c:8: undefined reference to `PyRun_SimpleStringFlags'
/home/miguellissimo/embedpy.c:11: undefined reference to `Py_Finalize'
collect2: error: ld returned 1 exit status

I can't find out what I am doing wrong or what I forget to get the example working.

PS: The python2.7-config command gives the following output on my Xubuntu machine:

>>> python2.7-config --cflags 
-I/usr/include/python2.7 -I/usr/include/x86_64-linux-gnu/python2.7  -fno-stri
ct-aliasing -D_FORTIFY_SOURCE=2 -g -fstack-protector --param=ssp-buffer-size=
4 -Wformat -Werror=format-security  -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-pr
ototypes

>>> python2.7-config --ldflags
-L/usr/lib/python2.7/config-x86_64-linux-gnu -L/usr/lib -lpthread -ldl  -luti
l -lm  -lpython2.7 -Xlinker -export-dynamic -Wl,-O1 -Wl,-Bsymbolic-functions 

Answer

nos picture nos · Dec 28, 2014

Libraries have to come after the object files when you are linking, so do:

gcc  embedpy.o $(/usr/bin/python2.7-config --ldflags)