#!/usr/bin/env python3
"""Check custom_mro's C89 declaration and lookup/decref evaluation order."""
import re
from pathlib import Path

source = Path("cpython/Objects/typeobject.c").read_text()
start = source.index("type_mro_modified(PyTypeObject *type, PyObject *bases) {")
end = source.index("\n}", start)
function = source[start:end]
start = function.index("    if (custom) {")
end = function.index("\n    n = PyTuple_GET_SIZE(bases);", start)
block = function[start:end]
assert re.match(
    r"if \(custom\) \{\s*PyObject \*mro_meth, \*type_mro_meth;\s*"
    r"int custom_mro;\s*mro_meth =",
    block.strip(),
), "custom_mro must be declared in the opening declaration block"
assert len(re.findall(r"\bint\s+custom_mro\b", function)) == 1, (
    "declare custom_mro exactly once"
)
expected = """
    if (custom) {
        PyObject *mro_meth, *type_mro_meth;
        int custom_mro;
        mro_meth = lookup_maybe_method(
            (PyObject *)type, &_Py_ID(mro), &unbound);
        if (mro_meth == NULL) {
            goto clear;
        }
        type_mro_meth = lookup_maybe_method(
            (PyObject *)&PyType_Type, &_Py_ID(mro), &unbound);
        if (type_mro_meth == NULL) {
            Py_DECREF(mro_meth);
            goto clear;
        }
        custom_mro = (mro_meth != type_mro_meth);
        Py_DECREF(mro_meth);
        Py_DECREF(type_mro_meth);
        if (custom_mro) {
            goto clear;
        }
    }
"""
assert block.split() == expected.split(), (
    "preserve both successful lookups before custom_mro assignment, "
    "then decrefs and conditional, including lookup failure handling"
)
print("type_mro_modified custom_mro C89 declaration and evaluation order: PASS")