cpython/Modules/testcapi_long.h

/* Poor-man's template.  Macros used:
   TESTNAME	name of the test (like test_long_api_inner)
   TYPENAME	the signed type (like long)
   F_S_TO_PY	convert signed to pylong; TYPENAME -> PyObject*
   F_PY_TO_S	convert pylong to signed; PyObject* -> TYPENAME
   F_U_TO_PY	convert unsigned to pylong; unsigned TYPENAME -> PyObject*
   F_PY_TO_U    convert pylong to unsigned; PyObject* -> unsigned TYPENAME
*/

static PyObject *
TESTNAME(PyObject *error(const char*))
{
	const int NBITS = sizeof(TYPENAME) * 8;
	unsigned TYPENAME base;
	PyObject *pyresult;
	int i;

	/* Note:  This test lets PyObjects leak if an error is raised.  Since
	   an error should never be raised, leaks are impossible <wink>. */

	/* Test native -> PyLong -> native roundtrip identity.
	 * Generate all powers of 2, and test them and their negations,
	 * plus the numbers +-1 off from them.
	 */
	base = 1;
	for (i = 0;
	     i < NBITS + 1;  /* on last, base overflows to 0 */
	     ++i, base <<= 1)
	{
		int j;
		for (j = 0; j < 6; ++j) {
			TYPENAME in, out;
			unsigned TYPENAME uin, uout;

			/* For 0, 1, 2 use base; for 3, 4, 5 use -base */
			uin = j < 3 ? base
				    : (unsigned TYPENAME)(-(TYPENAME)base);

			/* For 0 & 3, subtract 1.
			 * For 1 & 4, leave alone.
			 * For 2 & 5, add 1.
			 */
			uin += (unsigned TYPENAME)(TYPENAME)(j % 3 - 1);

			pyresult = F_U_TO_PY(uin);
			if (pyresult == NULL)
				return error(
				 "unsigned unexpected null result");

			uout = F_PY_TO_U(pyresult);
			if (uout == (unsigned TYPENAME)-1 && PyErr_Occurred())
				return error(
					"unsigned unexpected -1 result");
			if (uout != uin)
				return error(
					"unsigned output != input");
			UNBIND(pyresult);

			in = (TYPENAME)uin;
			pyresult = F_S_TO_PY(in);
			if (pyresult == NULL)
				return error(
					"signed unexpected null result");

			out = F_PY_TO_S(pyresult);
			if (out == (TYPENAME)-1 && PyErr_Occurred())
				return error(
					"signed unexpected -1 result");
			if (out != in)
				return error(
					"signed output != input");
			UNBIND(pyresult);
		}
	}

	/* Overflow tests.  The loop above ensured that all limit cases that
	 * should not overflow don't overflow, so all we need to do here is
	 * provoke one-over-the-limit cases (not exhaustive, but sharp).
	 */
	{
		PyObject *one, *x, *y;
		TYPENAME out;
		unsigned TYPENAME uout;

		one = PyLong_FromLong(1);
		if (one == NULL)
			return error(
				"unexpected NULL from PyLong_FromLong");

		/* Unsigned complains about -1? */
		x = PyNumber_Negative(one);
		if (x == NULL)
			return error(
				"unexpected NULL from PyNumber_Negative");

		uout = F_PY_TO_U(x);
		if (uout != (unsigned TYPENAME)-1 || !PyErr_Occurred())
			return error(
				"PyLong_AsUnsignedXXX(-1) didn't complain");
		PyErr_Clear();
		UNBIND(x);

		/* Unsigned complains about 2**NBITS? */
		y = PyLong_FromLong((long)NBITS);
		if (y == NULL)
			return error(
				"unexpected NULL from PyLong_FromLong");

		x = PyNumber_Lshift(one, y); /* 1L << NBITS, == 2**NBITS */
		UNBIND(y);
		if (x == NULL)
			return error(
				"unexpected NULL from PyNumber_Lshift");

  		uout = F_PY_TO_U(x);
		if (uout != (unsigned TYPENAME)-1 || !PyErr_Occurred())
			return error(
				"PyLong_AsUnsignedXXX(2**NBITS) didn't "
				"complain");
		PyErr_Clear();

		/* Signed complains about 2**(NBITS-1)?
		   x still has 2**NBITS. */
		y = PyNumber_Rshift(x, one); /* 2**(NBITS-1) */
		UNBIND(x);
		if (y == NULL)
			return error(
				"unexpected NULL from PyNumber_Rshift");

		out = F_PY_TO_S(y);
		if (out != (TYPENAME)-1 || !PyErr_Occurred())
			return error(
				"PyLong_AsXXX(2**(NBITS-1)) didn't "
				"complain");
		PyErr_Clear();

		/* Signed complains about -2**(NBITS-1)-1?;
		   y still has 2**(NBITS-1). */
		x = PyNumber_Negative(y);  /* -(2**(NBITS-1)) */
		UNBIND(y);
		if (x == NULL)
			return error(
				"unexpected NULL from PyNumber_Negative");

		y = PyNumber_Subtract(x, one); /* -(2**(NBITS-1))-1 */
		UNBIND(x);
		if (y == NULL)
			return error(
				"unexpected NULL from PyNumber_Subtract");

		out = F_PY_TO_S(y);
		if (out != (TYPENAME)-1 || !PyErr_Occurred())
			return error(
				"PyLong_AsXXX(-2**(NBITS-1)-1) didn't "
				"complain");
		PyErr_Clear();
		UNBIND(y);

		Py_XDECREF(x);
		Py_XDECREF(y);
		Py_DECREF(one);
	}

	Py_INCREF(Py_None);
	return Py_None;
}