gh-137725: Convert faulthandler to Argument Clinic

[vstinner]

• Issue: Convert faulthandler extension to Argument Clinic #137725

[ZeroIntensity]

I don't understand this test failure. EXCEPTION_ACCESS_VIOLATION should be defined as 0xC0000005 on Windows, which isn't negative.

[colesbury]

EXCEPTION_ACCESS_VIOLATION is >2**31 so when it's cast to a long, which is signed and only 32-bits on Windows, it becomes negative:

cpython/Modules/faulthandler.c

Lines 1330 to 1333 in a10152f

	if (PyModule_AddIntConstant(module, "_EXCEPTION_ACCESS_VIOLATION",
	EXCEPTION_ACCESS_VIOLATION)) {
	return -1;
	}

cpython/Include/modsupport.h

Line 39 in a10152f

PyAPI_FUNC(int) PyModule_AddIntConstant(PyObject *, const char *, long);

[ZeroIntensity]

Ah, and it seems that PyArg_ParseTuple allows negative values for whatever reason (but AC doesn't):

static PyObject *
foo(PyObject *self, PyObject *args)
{
    unsigned int a;
    if (!PyArg_ParseTuple(args, "I", &a)) {
        return NULL;
    }
    printf("a: %u\n", a);

    Py_RETURN_NONE;
}

>>> foo(-1)
a: 4294967295

Yuck.

[vstinner]

I fixed the Windows EXCEPTION constants by using PyLong_FromUnsignedLong(). Constants and _raise_exception() are only defined for test_faulthandler, so it's ok to no longer accept negative values.

[vstinner]

Ok, the CI does now pass. The PR is now ready for a review :-) Sorry, I should have marked it as a draft in the beginning.

[ZeroIntensity]

LGTM

[serhiy-storchaka]

This PR includes also some behavior changes (constants are positive, negative arguments rejected), so I think it may need a NEWS entry.

Or you can keep the old behavior and change it in the following PR.

[vstinner]

This PR includes also some behavior changes (constants are positive, negative arguments rejected), so I think it may need a NEWS entry.

These changes only concern private functions and private constants, so I consider that they should not be documented. End users are not impacted, these functions and constants are only used by tests.

[serhiy-storchaka]

LGTM. 👍

[vstinner]

Merged, thanks for your very useful reviews!