port: advance VC6 typeobject frontier and preserve regression coverage

scripts/vc6-tupleobject-alloc-c89.test.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+"""Check tuple_alloc's C89 declaration and validation/allocation order."""
+import re
+import sys
+from pathlib import Path
+
+source = Path(sys.argv[1] if len(sys.argv) > 1 else "cpython/Objects/tupleobject.c")
+match = re.search(
+    r"static PyTupleObject \*\ntuple_alloc\(Py_ssize_t size\)\n\{(.*?)\n\}",
+    source.read_text(),
+    re.S,
+)
+assert match, "tuple_alloc definition not found"
+body = match.group(1)
+assert re.match(r"\s*PyTupleObject \*op;", body), (
+    "tuple_alloc: op must be declared without initializer before the size check; "
+    "declaration after statement is not C89 compatible"
+)
+expected = """
+    PyTupleObject *op;
+    if (size < 0) {
+        PyErr_BadInternalCall();
+        return NULL;
+    }
+#ifdef Py_DEBUG
+    assert(size != 0);    // The empty tuple is statically allocated.
+#endif
+
+    op = maybe_freelist_pop(size);
+    if (op == NULL) {
+        /* Check for overflow */
+        if ((size_t)size > ((size_t)PY_SSIZE_T_MAX - (sizeof(PyTupleObject) -
+                    sizeof(PyObject *))) / sizeof(PyObject *)) {
+            return (PyTupleObject *)PyErr_NoMemory();
+        }
+        op = PyObject_GC_NewVar(PyTupleObject, &PyTuple_Type, size);
+        if (op == NULL)
+            return NULL;
+    }
+    return op;
+"""
+assert re.sub(r"\s+", "", body) == re.sub(r"\s+", "", expected), (
+    "preserve size validation, debug assertion, single freelist lookup, overflow "
+    "check, GC allocation, error/return order, and absence of refcount operations"
+)
+print("tuple_alloc C89 declaration and validation/allocation order: PASS")