A minimal Python module in C, with MinGW makefile

cpytest.c

#define PY_SSIZE_T_CLEAN
#include <Python.h>

#include <stddef.h>

PyObject *cpytest_add(PyObject *module, PyObject *args)
{
    PyObject *lhs, *rhs;
    if (!PyArg_ParseTuple(args, "OO", &lhs, &rhs))
        return NULL;

    return PyNumber_Add(lhs, rhs);
}

PyObject *cpytest_addi(PyObject *module, PyObject *args)
{
    long lhs, rhs;
    if (!PyArg_ParseTuple(args, "ll", &lhs, &rhs))
        return NULL;

    return PyLong_FromLong(lhs + rhs);
}

PyMethodDef cpytest_methods[] = {
    { "add", cpytest_add, METH_VARARGS, "add two things" },
    { "addi", cpytest_addi, METH_VARARGS, "add two integers" },
    { NULL, NULL, 0, NULL },
};

struct PyModuleDef cpytest = {
    PyModuleDef_HEAD_INIT,
    "cpytest",
    NULL,
    -1,
    cpytest_methods
};

PyMODINIT_FUNC
PyInit_cpytest(void)
{
    return PyModule_Create(&cpytest);
}

Makefile

CC=gcc
COPTS=-Wall -pedantic -std=c99 -O2 -static
PYROOT=C:/Users/Derrick/local
PYVER=36
PYINCLUDEDIR=$(PYROOT)/Python$(PYVER)/include
PYLIBDIR=$(PYROOT)/Python$(PYVER)/libs

cpytest.pyd: cpytest.c
	$(CC) $(COPTS) -shared -I$(PYINCLUDEDIR) -L$(PYLIBDIR) -o $@ $^ -lpython$(PYVER)