port: advance VC6 typeobject frontier and preserve regression coverage

scripts/vc6-obmalloc-insert-to-usedpool-c89.test.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env python3
+"""Guard only insert_to_usedpool's entry locals and original operation order."""
+
+import re
+import sys
+from pathlib import Path
+
+source = Path(sys.argv[1]).read_text()
+match = re.search(
+    r"\ninsert_to_usedpool\(poolp pool\)\s*\{(.*?)\n\}",
+    source, re.S,
+)
+assert match, "insert_to_usedpool definition not found"
+body = re.sub(r"/\*.*?\*/", "", match.group(1), flags=re.S)
+declarations = """
+    uint size;
+    poolp next;
+    poolp prev;
+"""
+assert body.split()[:len(declarations.split())] == declarations.split(), (
+    "insert_to_usedpool must declare size, next, and prev without initializers at function entry"
+)
+
+# Keep the assertion before size evaluation and both lookups, then preserve
+# the four pointer-link writes in their original order.
+expected = declarations + """
+    assert(pool->ref.count > 0);
+    size = pool->szidx;
+    next = usedpools[size + size];
+    prev = next->prevpool;
+    pool->nextpool = next;
+    pool->prevpool = prev;
+    next->prevpool = pool;
+    prev->nextpool = pool;
+"""
+assert body.split() == expected.split(), (
+    "preserve insert_to_usedpool assertion, size/lookup evaluation, and pointer-link mutation order"
+)
+print("obmalloc insert_to_usedpool entry declarations and original operation order: PASS")