python - c pointers and ctypes -

so, have c++ class wrap in c can use in python using ctypes. declaration of c++ class:

// test.h class test { public:    static double add(double a, double b); };   //test.cpp #include "stdafx.h" #include "test.h"  double test::add(double a, double b) {    return + b; } 

c wrap:

// cdll.h #ifndef wrapdll_exports #define wrapdll_api __declspec(dllexport)  #else #define wrapdll_api __declspec(dllimport)  #endif  #include "test.h" extern "c" {    wrapdll_api struct testc;     wrapdll_api testc* newtest();    wrapdll_api double addc(testc* pc, double a, double b); }  //cdll.cpp #include "stdafx.h" #include "cdll.h"  testc* newtest() {    return (testc*) new test; }  double addc(testc* pc, double a, double b) {    return ((test*)pc)->add(a, b); } 

python script:

import ctypes t = ctypes.cdll('../debug/cdll.dll') = t.newtest() t.addc(a, 2, 3) 

result of t.addc(a, 2, 3) negative integer. there problem pointer, not know problem. have ideas?

as addc static function pointer not problem.

you need pass double values addc, , double type back:

t.addc.restype = c_double t.addc(a, c_double(2), c_double(3)) 

the documentation ctype explains this.