port: advance VC6 compatibility frontier

scripts/vc6-bytearray-join-c89.test.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python3
+"""Source-level C89 and ownership-order check for bytearray_join."""
+import re
+import sys
+from pathlib import Path
+
+if len(sys.argv) != 2:
+    raise SystemExit("usage: vc6-bytearray-join-c89.test.py bytearrayobject.c")
+source = Path(sys.argv[1]).read_text()
+signature = "bytearray_join(PyByteArrayObject *self, PyObject *iterable_of_bytes)"
+start = source.index(signature)
+body_start = source.index("{", start)
+body_end = source.index("\n}", body_start)
+body = source[body_start + 1:body_end]
+
+if not body.lstrip().startswith("PyObject *ret;"):
+    raise SystemExit("ret must be declared in bytearray_join's opening declaration group")
+if len(re.findall(r"\bPyObject\s*\*\s*ret\s*;", body)) != 1:
+    raise SystemExit("bytearray_join must declare ret exactly once")
+if re.search(r"\bPyObject\s*\*\s*ret\s*=", body):
+    raise SystemExit("bytearray_join must assign ret separately from its declaration")
+pattern = re.compile(
+    r"self->ob_exports\+\+;.*?"
+    r"ret\s*=\s*stringlib_bytes_join\(\s*\(PyObject\*\)self,\s*"
+    r"iterable_of_bytes\s*\);\s*"
+    r"self->ob_exports--;\s*(?://[^\n]*\s*)?return ret;",
+    re.DOTALL,
+)
+if not pattern.search(body):
+    raise SystemExit("bytearray_join export/join/unexport/return order changed")
+print("bytearray_join C89 declaration and export order: PASS")