SWIG - C++ code in python

Question

I tried to import the SWING generated module, but I got an ImportError:

>>> import ava
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "ava.py", line 28, in <module>
    _ava = swig_import_helper()
  File "ava.py", line 24, in swig_import_helper
    _mod = imp.load_module('_ava', fp, pathname, description)
ImportError: ./_ava.so: undefined symbol: _Z7turn_aiPPiiii
>>>

I followed SWIG's tutorial (http://www.swig.org/tutorial.html) and I compiled my main.cpp like this:

swig -python -c++ ava.i
c++ -fPIC -c ava_wrap.cxx -I/usr/include/python2.7/
c++ -shared ava_wrap.o -o _ava.so

and I tried to extern my functions to c:

extern "C" {
  bool isEnd(int** t, int x, int y, int K, int J);
  void tout(int** t, int K);
  koord turn(int** t, int player, int K, int J);
  koord turn_ai(int** t, int player, int K, int J);
  bool isPat(int** t, int K);
  ai_res turn_ai_3x3_v2(int** t, int turn);
  ai_res turn_ai_pre(int** t, int turn, int K, int J, int dep);
  ai_res turn_ai_(int** t, int turn, int K, int J, int ab, int dep);
  bool isSeparated(int** t, int K, int i, int j);
  std::vector<koord> stepsFun(int** t, int K);
  bool isEmpty(int** t, int K);
  int value(int** t, int K);
  int fofug();
}

Now I modified my ava.i from /* ava.i */ %module ava %{ /* Put header files here or function declarations like below */ #include "koord.h" extern koord turn_ai(int** t, int player, int K, int J); %} %include "koord.h" extern koord turn_ai(int** t, int player, int K, int J); to /* ava.i */ %module ava %{ /* Put header files here or function declarations like below */ #include "koord.h" extern "C" koord turn_ai(int** t, int player, int K, int J); %} %include "koord.h" extern "C" koord turn_ai(int** t, int player, int K, int J); — buduboti
– buduboti, Commented May 24, 2018 at 12:39
But it's still the same error, just the end is now undefined symbol: turn_ai — buduboti
– buduboti, Commented May 24, 2018 at 12:42

Catalin P · Accepted Answer · 2018-07-21 04:52:43Z

1

The problem is with the c++ commands. Your _ava.so contains the SWIG wrappers, but is missing the implementations for turn_ai etc.

Look carefully at the SWIG Tutorial, there are example.c and example.o which contain implementations of fact, my_mod, etc.

answered Jul 21, 2018 at 4:52

Catalin P

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