CPython testing

.gitignore

*.o
*.o
primes.*.so

Makefile

PYTHON = python

CPYARCH = $(shell $(PYTHON) -c \
	'import sys;i=sys.implementation;print(i.cache_tag+"-"+i._multiarch)')
PYTHONLIB = python$(shell $(PYTHON) --version | cut -d' ' -f2 | cut -d'.' -f1,2)

# Warnings
CFLAGS += -Wno-unused-result -Wsign-compare -Wall -Wformat -Werror=format-security
# Debugging
CFLAGS += -DNDEBUG -g
# Optimisation
CFLAGS += -fwrapv -O3 -march=x86-64 -mtune=generic -fno-plt -flto=auto -ffat-lto-objects
LDFLAGS += -Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now -flto=auto
# Build flags
CFLAGS += -pipe
# Hardening
CFLAGS += -Wp,-D_FORTIFY_SOURCE=2 -fstack-clash-protection -fcf-protection

.PHONY: run
run: primestest.py primes.$(CPYARCH).so
	$(PYTHON) $<

primes.$(CPYARCH).so: primesmodule.o primes.o
	$(CC) -shared $(LDFLAGS) $^ -o $@

primesmodule.o: primesmodule.c primes.h
	$(CC) $(CFLAGS) -fPIC -I/usr/include/$(PYTHONLIB) -c $< -o $@

primes.o: primes.c primes.h

.PHONY: clean
clean:
	rm -f *.o *.so

primes.c

#include <math.h>

#include "primes.h"

int
is_prime(int n)
{
	int bound;

	if (n < 2 || (n > 2 && n % 2 == 0))
		return 0;

	bound = sqrt(n);

	for (int i = 3; i <= bound; i += 2) {
		if (n % i == 0)
			return 0;
	}

	return 1;
}

primes.h

int is_prime(int n);

primesmodule.c

#define PY_SSIZE_T_CLEAN
#include <Python.h>

#include "primes.h"

static PyObject *
primes_is_prime(PyObject *self, PyObject *args)
{
	int n;

	if (!PyArg_ParseTuple(args, "i", &n))
		return NULL;

	if (is_prime(n)) {
		Py_INCREF(Py_True);
		return Py_True;
	} else {
		Py_INCREF(Py_False);
		return Py_False;
	}
}

static PyMethodDef PrimesMethods[] = {
	{"is_prime", primes_is_prime, METH_VARARGS, "Prime test"},
	{NULL, NULL, 0, NULL}
};

static struct PyModuleDef primesmodule = {
	PyModuleDef_HEAD_INIT,
	"primes",
	NULL,
	-1,
	PrimesMethods
};

PyMODINIT_FUNC
PyInit_primes(void)
{
	return PyModule_Create(&primesmodule);
}

primestest.py

import primes

for i in range(1, 21):
    print(i, primes.is_prime(i), sep = "\t")