Calling Cython function from C code raises segmentation fault

Question

I\'m trying to call cython (cdef) function in C program. When the cdef function contains python statements, e.g. print(0.5), or python (def) functions, calling the (cdef) fu

Answer 1

I guess you are using Cython 0.29. Since 0.29, PEP-489 multi-phase module initialisation has been enabled for Python versions >=3.5. This means, using PyInit_XXX is no longer sufficient, as you are experiencing.

Cython's documentation suggest to use inittab mechanism, i.e. your main-function should look something like:

#include "Python.h"
#include "transcendentals.h"
#include 
#include 

int main(int argc, char **argv) {
  int status=PyImport_AppendInittab("transcendentals", PyInit_transcendentals);
  if(status==-1){
    return -1;//error
  } 
  Py_Initialize();
  PyObject *module = PyImport_ImportModule("transcendentals");

  if(module==NULL){
     Py_Finalize();
     return -1;//error
  }

  printf("pi**e: %f\n", pow(PI, get_e()));
  Py_Finalize();
  return 0;
}

Another possibility to restore the old behavior would be to define macro CYTHON_PEP489_MULTI_PHASE_INIT=0 and thus overriding the default by e.g. passing -DCYTHON_PEP489_MULTI_PHASE_INIT=0 to gcc on the command line.