#!/usr/bin/env python3
"""Guard _PyMem_DebugCheckAddress's C89 locals and validation order."""

import re
import sys
from pathlib import Path

source = Path(sys.argv[1]).read_text()
match = re.search(
    r"\n_PyMem_DebugCheckAddress\(const char \*func, char api, const void \*p\)\s*\{(.*?)\n\}",
    source, re.S,
)
assert match, "_PyMem_DebugCheckAddress definition not found"
body = re.sub(r"/\*.*?\*/", "", match.group(1), flags=re.S)
declarations = """
    const uint8_t *q;
    size_t nbytes;
    const uint8_t *tail;
    int i;
    char id;
"""
assert body.split()[:len(declarations.split())] == declarations.split(), (
    "_PyMem_DebugCheckAddress must declare all locals without initializers at function entry"
)

# Keep the pointer cast after the assertion, and validate the leading pad
# before reading the size or checking the tail of a possibly corrupt block.
expected = declarations + """
    assert(p != NULL);
    q = (const uint8_t *)p;
    id = (char)q[-SST];
    if (id != api) {
        _PyObject_DebugDumpAddress(p);
        _Py_FatalErrorFormat(func,
                             "bad ID: Allocated using API '%c', "
                             "verified using API '%c'",
                             id, api);
    }
    for (i = SST-1; i >= 1; --i) {
        if (*(q-i) != PYMEM_FORBIDDENBYTE) {
            _PyObject_DebugDumpAddress(p);
            _Py_FatalErrorFunc(func, "bad leading pad byte");
        }
    }
    nbytes = read_size_t(q - 2*SST);
    tail = q + nbytes;
    for (i = 0; i < SST; ++i) {
        if (tail[i] != PYMEM_FORBIDDENBYTE) {
            _PyObject_DebugDumpAddress(p);
            _Py_FatalErrorFunc(func, "bad trailing pad byte");
        }
    }
"""
assert body.split() == expected.split(), (
    "preserve _PyMem_DebugCheckAddress assertion, cast evaluation point, "
    "and complete validation/diagnostic order"
)
print("obmalloc _PyMem_DebugCheckAddress C89 declarations and original validation order: PASS")