#!/usr/bin/env python3
"""Guard VC6-compatible default allocator copies, fields, and call order."""

import re
import sys
from pathlib import Path

source = Path(sys.argv[1]).read_text()
# Preserve ctx/malloc/calloc/realloc/free and WITH_PYMALLOC selection.
macros = source[source.index("#define MALLOC_ALLOC"):source.index("typedef struct {", source.index("#define MALLOC_ALLOC"))]
expected_macros = """
#define MALLOC_ALLOC {NULL, _PyMem_RawMalloc, _PyMem_RawCalloc, _PyMem_RawRealloc, _PyMem_RawFree}
#ifdef WITH_PYMALLOC
#  define PYMALLOC_ALLOC {NULL, _PyObject_Malloc, _PyObject_Calloc, _PyObject_Realloc, _PyObject_Free}
#endif
#define PYRAW_ALLOC MALLOC_ALLOC
#ifdef WITH_PYMALLOC
#  define PYOBJ_ALLOC PYMALLOC_ALLOC
#else
#  define PYOBJ_ALLOC MALLOC_ALLOC
#endif
#define PYMEM_ALLOC PYOBJ_ALLOC
"""
assert macros.split() == expected_macros.split(), (
    "default allocator fields or WITH_PYMALLOC selection changed"
)

match = re.search(
    r"\npymem_set_default_allocator\([^)]*\)\s*\{(.*?)\n\}", source, re.S
)
assert match, "pymem_set_default_allocator definition not found"
body = re.sub(r"/\*.*?\*/", "", match.group(1), flags=re.S)
declaration = "PyMemAllocatorEx new_alloc;"
if body.count(declaration) != 1 or not body.lstrip().startswith(declaration):
    sys.exit("new_alloc must be declared once without initializer at function entry")

expected = """
    if (old_alloc != NULL) {
        PyMem_GetAllocator(domain, old_alloc);
    }
    switch(domain)
    {
    case PYMEM_DOMAIN_RAW:
    {
        PyMemAllocatorEx alloc = PYRAW_ALLOC;
        new_alloc = alloc;
        break;
    }
    case PYMEM_DOMAIN_MEM:
    {
        PyMemAllocatorEx alloc = PYMEM_ALLOC;
        new_alloc = alloc;
        break;
    }
    case PYMEM_DOMAIN_OBJ:
    {
        PyMemAllocatorEx alloc = PYOBJ_ALLOC;
        new_alloc = alloc;
        break;
    }
    default:
        return -1;
    }
    PyMem_SetAllocator(domain, &new_alloc);
    if (debug) {
        _PyMem_SetupDebugHooksDomain(domain);
    }
    return 0;
"""
if body.replace(declaration, "").split() != expected.split():
    sys.exit("default allocator switch, assignments, or call order changed")
print("obmalloc default allocator C89 assignments, allocator semantics, and execution order: PASS")