cdef public api char* say_hi():
    return "hello from python!"

#include <Python.h>
#include "hello.h"

int main() {
  Py_Initialize();
  char *hi = say_hi();
  printf("%sn", hi);
  Py_Finalize();
}

gcc `python2-config --cflags --ldflags` -o compiledhi sayhi.c

Undefined symbols for architecture x86_64:
  "_say_hi", referenced from:
      _main in sayhi-302608.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

gcc `python3-config --cflags --ldflags` -o compiledhi sayhi.c

#include <Python.h>
#include "hello_api.h"

int main() {
  Py_Initialize();
  import_hello();
  char *hi = say_hi();
  printf("%sn", hi);
  Py_Finalize();
}