{"abstract":"Interior pointers into moved objects end up offset by the distance the object moved.","category":"Garbage collector invariants","checks":6,"contract":"Relocate frame slots after a moving collection. Each frame has a safepoint pc and a slot list; maps[pc] gives a reference bitmask (bit i set means slot i holds a reference; bit 0 is slot 0) and derived pointers [derived_slot, base_slot], which hold base + offset and are not in the mask. moves maps old object addresses to new ones (unmoved objects are absent or map to themselves). Reference slots are relocated, derived slots become new base + (old derived - old base), and every other slot is left untouched. A pc without a map returns [\"no-stackmap\", pc].","contract_signature":"frames, maps, moves","evaluation_group":"w2-garbage-collector-invariants-stack-map-relocation","failed_approach":"Using the derived value itself as the base treats it as an exact object pointer.","family":"w2-garbage-collector-invariants-stack-map-relocation-derived-base-value","id":"FA-90601","implementations":{"attempt":{"sha256":"6e7425046cbc958aabeb576846444e38162491203f5ca45252c2296cf1e8a53c","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(frames, maps, moves):\n    out = []\n    for f in frames:\n        key = f['pc']\n        if key not in maps:\n            return ['no-stackmap', key]\n        m = maps[key]\n        old = list(f['slots'])\n        slots = list(old)\n        for i in range(len(slots)):\n            if m['refs'] >> i & 1 and old[i] is not None:\n                slots[i] = moves.get(old[i], old[i])\n        for dslot, bslot in m['derived']:\n            base = old[dslot]\n            slots[dslot] = moves.get(base, base) + (old[dslot] - base)\n        out.append(slots)\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncases = [[('regression: references, integers and derived pointers',\n   ([{'pc': 10, 'slots': [1000, 8, 2000, 1016, 1000, 1992]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5016, 2000: 2400, 3000: 3000}),\n   [[5016, 8, 2400, 5032, 1000, 2392]]),\n  ('integer that looks like a moved address',\n   ([{'pc': 20, 'slots': [2000, 1000, 3001]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5016, 2000: 2400, 3000: 3000}),\n   [[2000, 5016, 3001]]),\n  ('derived pointer below its base',\n   ([{'pc': 30, 'slots': [None, 2000, 1989]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5016, 2000: 2400, 3000: 3000}),\n   [[None, 2400, 2389]]),\n  ('several frames',\n   ([{'pc': 20, 'slots': [5, 2000, 9]}, {'pc': 30, 'slots': [1000, 3000, 3005]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5016, 2000: 2400, 3000: 3000}),\n   [[5, 2400, 9], [5016, 3000, 3005]]),\n  ('missing stack map',\n   ([{'pc': 20, 'slots': [1, 2, 3]}, {'pc': 12, 'slots': []}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5016, 2000: 2400, 3000: 3000}),\n   ['no-stackmap', 12]),\n  ('control: null reference slots',\n   ([{'pc': 20, 'slots': [1, None, 0]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5016, 2000: 2400, 3000: 3000}),\n   [[1, None, 0]])],\n [('regression: references, integers and derived pointers',\n   ([{'pc': 10, 'slots': [1000, 9, 2000, 1016, 1000, 1992]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5032, 2000: 2400, 3000: 3000}),\n   [[5032, 9, 2400, 5048, 1000, 2392]]),\n  ('integer that looks like a moved address',\n   ([{'pc': 20, 'slots': [2000, 1000, 3002]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5032, 2000: 2400, 3000: 3000}),\n   [[2000, 5032, 3002]]),\n  ('derived pointer below its base',\n   ([{'pc': 30, 'slots': [None, 2000, 1988]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5032, 2000: 2400, 3000: 3000}),\n   [[None, 2400, 2388]]),\n  ('several frames',\n   ([{'pc': 20, 'slots': [5, 2000, 9]}, {'pc': 30, 'slots': [1000, 3000, 3006]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5032, 2000: 2400, 3000: 3000}),\n   [[5, 2400, 9], [5032, 3000, 3006]]),\n  ('missing stack map',\n   ([{'pc': 20, 'slots': [1, 2, 3]}, {'pc': 13, 'slots': []}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5032, 2000: 2400, 3000: 3000}),\n   ['no-stackmap', 13]),\n  ('control: null reference slots',\n   ([{'pc': 20, 'slots': [2, None, 0]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5032, 2000: 2400, 3000: 3000}),\n   [[2, None, 0]])],\n [('regression: references, integers and derived pointers',\n   ([{'pc': 10, 'slots': [1000, 10, 2000, 1016, 1000, 1992]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5048, 2000: 2400, 3000: 3000}),\n   [[5048, 10, 2400, 5064, 1000, 2392]]),\n  ('integer that looks like a moved address',\n   ([{'pc': 20, 'slots': [2000, 1000, 3003]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5048, 2000: 2400, 3000: 3000}),\n   [[2000, 5048, 3003]]),\n  ('derived pointer below its base',\n   ([{'pc': 30, 'slots': [None, 2000, 1987]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5048, 2000: 2400, 3000: 3000}),\n   [[None, 2400, 2387]]),\n  ('several frames',\n   ([{'pc': 20, 'slots': [5, 2000, 9]}, {'pc': 30, 'slots': [1000, 3000, 3007]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5048, 2000: 2400, 3000: 3000}),\n   [[5, 2400, 9], [5048, 3000, 3007]]),\n  ('missing stack map',\n   ([{'pc': 20, 'slots': [1, 2, 3]}, {'pc': 14, 'slots': []}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5048, 2000: 2400, 3000: 3000}),\n   ['no-stackmap', 14]),\n  ('control: null reference slots',\n   ([{'pc': 20, 'slots': [3, None, 0]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5048, 2000: 2400, 3000: 3000}),\n   [[3, None, 0]])],\n [('regression: references, integers and derived pointers',\n   ([{'pc': 10, 'slots': [1000, 11, 2000, 1016, 1000, 1992]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5064, 2000: 2400, 3000: 3000}),\n   [[5064, 11, 2400, 5080, 1000, 2392]]),\n  ('integer that looks like a moved address',\n   ([{'pc': 20, 'slots': [2000, 1000, 3004]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5064, 2000: 2400, 3000: 3000}),\n   [[2000, 5064, 3004]]),\n  ('derived pointer below its base',\n   ([{'pc': 30, 'slots': [None, 2000, 1986]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5064, 2000: 2400, 3000: 3000}),\n   [[None, 2400, 2386]]),\n  ('several frames',\n   ([{'pc': 20, 'slots': [5, 2000, 9]}, {'pc': 30, 'slots': [1000, 3000, 3008]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5064, 2000: 2400, 3000: 3000}),\n   [[5, 2400, 9], [5064, 3000, 3008]]),\n  ('missing stack map',\n   ([{'pc': 20, 'slots': [1, 2, 3]}, {'pc': 15, 'slots': []}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5064, 2000: 2400, 3000: 3000}),\n   ['no-stackmap', 15]),\n  ('control: null reference slots',\n   ([{'pc': 20, 'slots': [4, None, 0]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5064, 2000: 2400, 3000: 3000}),\n   [[4, None, 0]])],\n [('regression: references, integers and derived pointers',\n   ([{'pc': 10, 'slots': [1000, 12, 2000, 1016, 1000, 1992]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5080, 2000: 2400, 3000: 3000}),\n   [[5080, 12, 2400, 5096, 1000, 2392]]),\n  ('integer that looks like a moved address',\n   ([{'pc': 20, 'slots': [2000, 1000, 3005]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5080, 2000: 2400, 3000: 3000}),\n   [[2000, 5080, 3005]]),\n  ('derived pointer below its base',\n   ([{'pc': 30, 'slots': [None, 2000, 1985]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5080, 2000: 2400, 3000: 3000}),\n   [[None, 2400, 2385]]),\n  ('several frames',\n   ([{'pc': 20, 'slots': [5, 2000, 9]}, {'pc': 30, 'slots': [1000, 3000, 3009]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5080, 2000: 2400, 3000: 3000}),\n   [[5, 2400, 9], [5080, 3000, 3009]]),\n  ('missing stack map',\n   ([{'pc': 20, 'slots': [1, 2, 3]}, {'pc': 16, 'slots': []}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5080, 2000: 2400, 3000: 3000}),\n   ['no-stackmap', 16]),\n  ('control: null reference slots',\n   ([{'pc': 20, 'slots': [5, None, 0]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5080, 2000: 2400, 3000: 3000}),\n   [[5, None, 0]])]]\nfor label, args, expected in cases[N - 1]:\n    check(label, solve(*args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"f5243bd109ce037dda3f81a89ed7d95b79794ebb3fd50054488f9defbee717d9","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(frames, maps, moves):\n    out = []\n    for f in frames:\n        key = f['pc']\n        if key not in maps:\n            return ['no-stackmap', key]\n        m = maps[key]\n        old = list(f['slots'])\n        slots = list(old)\n        for i in range(len(slots)):\n            if m['refs'] >> i & 1 and old[i] is not None:\n                slots[i] = moves.get(old[i], old[i])\n        for dslot, bslot in m['derived']:\n            base = slots[bslot]\n            slots[dslot] = moves.get(base, base) + (old[dslot] - base)\n        out.append(slots)\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncases = [[('regression: references, integers and derived pointers',\n   ([{'pc': 10, 'slots': [1000, 8, 2000, 1016, 1000, 1992]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5016, 2000: 2400, 3000: 3000}),\n   [[5016, 8, 2400, 5032, 1000, 2392]]),\n  ('integer that looks like a moved address',\n   ([{'pc': 20, 'slots': [2000, 1000, 3001]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5016, 2000: 2400, 3000: 3000}),\n   [[2000, 5016, 3001]]),\n  ('derived pointer below its base',\n   ([{'pc': 30, 'slots': [None, 2000, 1989]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5016, 2000: 2400, 3000: 3000}),\n   [[None, 2400, 2389]]),\n  ('several frames',\n   ([{'pc': 20, 'slots': [5, 2000, 9]}, {'pc': 30, 'slots': [1000, 3000, 3005]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5016, 2000: 2400, 3000: 3000}),\n   [[5, 2400, 9], [5016, 3000, 3005]]),\n  ('missing stack map',\n   ([{'pc': 20, 'slots': [1, 2, 3]}, {'pc': 12, 'slots': []}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5016, 2000: 2400, 3000: 3000}),\n   ['no-stackmap', 12]),\n  ('control: null reference slots',\n   ([{'pc': 20, 'slots': [1, None, 0]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5016, 2000: 2400, 3000: 3000}),\n   [[1, None, 0]])],\n [('regression: references, integers and derived pointers',\n   ([{'pc': 10, 'slots': [1000, 9, 2000, 1016, 1000, 1992]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5032, 2000: 2400, 3000: 3000}),\n   [[5032, 9, 2400, 5048, 1000, 2392]]),\n  ('integer that looks like a moved address',\n   ([{'pc': 20, 'slots': [2000, 1000, 3002]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5032, 2000: 2400, 3000: 3000}),\n   [[2000, 5032, 3002]]),\n  ('derived pointer below its base',\n   ([{'pc': 30, 'slots': [None, 2000, 1988]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5032, 2000: 2400, 3000: 3000}),\n   [[None, 2400, 2388]]),\n  ('several frames',\n   ([{'pc': 20, 'slots': [5, 2000, 9]}, {'pc': 30, 'slots': [1000, 3000, 3006]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5032, 2000: 2400, 3000: 3000}),\n   [[5, 2400, 9], [5032, 3000, 3006]]),\n  ('missing stack map',\n   ([{'pc': 20, 'slots': [1, 2, 3]}, {'pc': 13, 'slots': []}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5032, 2000: 2400, 3000: 3000}),\n   ['no-stackmap', 13]),\n  ('control: null reference slots',\n   ([{'pc': 20, 'slots': [2, None, 0]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5032, 2000: 2400, 3000: 3000}),\n   [[2, None, 0]])],\n [('regression: references, integers and derived pointers',\n   ([{'pc': 10, 'slots': [1000, 10, 2000, 1016, 1000, 1992]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5048, 2000: 2400, 3000: 3000}),\n   [[5048, 10, 2400, 5064, 1000, 2392]]),\n  ('integer that looks like a moved address',\n   ([{'pc': 20, 'slots': [2000, 1000, 3003]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5048, 2000: 2400, 3000: 3000}),\n   [[2000, 5048, 3003]]),\n  ('derived pointer below its base',\n   ([{'pc': 30, 'slots': [None, 2000, 1987]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5048, 2000: 2400, 3000: 3000}),\n   [[None, 2400, 2387]]),\n  ('several frames',\n   ([{'pc': 20, 'slots': [5, 2000, 9]}, {'pc': 30, 'slots': [1000, 3000, 3007]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5048, 2000: 2400, 3000: 3000}),\n   [[5, 2400, 9], [5048, 3000, 3007]]),\n  ('missing stack map',\n   ([{'pc': 20, 'slots': [1, 2, 3]}, {'pc': 14, 'slots': []}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5048, 2000: 2400, 3000: 3000}),\n   ['no-stackmap', 14]),\n  ('control: null reference slots',\n   ([{'pc': 20, 'slots': [3, None, 0]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5048, 2000: 2400, 3000: 3000}),\n   [[3, None, 0]])],\n [('regression: references, integers and derived pointers',\n   ([{'pc': 10, 'slots': [1000, 11, 2000, 1016, 1000, 1992]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5064, 2000: 2400, 3000: 3000}),\n   [[5064, 11, 2400, 5080, 1000, 2392]]),\n  ('integer that looks like a moved address',\n   ([{'pc': 20, 'slots': [2000, 1000, 3004]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5064, 2000: 2400, 3000: 3000}),\n   [[2000, 5064, 3004]]),\n  ('derived pointer below its base',\n   ([{'pc': 30, 'slots': [None, 2000, 1986]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5064, 2000: 2400, 3000: 3000}),\n   [[None, 2400, 2386]]),\n  ('several frames',\n   ([{'pc': 20, 'slots': [5, 2000, 9]}, {'pc': 30, 'slots': [1000, 3000, 3008]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5064, 2000: 2400, 3000: 3000}),\n   [[5, 2400, 9], [5064, 3000, 3008]]),\n  ('missing stack map',\n   ([{'pc': 20, 'slots': [1, 2, 3]}, {'pc': 15, 'slots': []}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5064, 2000: 2400, 3000: 3000}),\n   ['no-stackmap', 15]),\n  ('control: null reference slots',\n   ([{'pc': 20, 'slots': [4, None, 0]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5064, 2000: 2400, 3000: 3000}),\n   [[4, None, 0]])],\n [('regression: references, integers and derived pointers',\n   ([{'pc': 10, 'slots': [1000, 12, 2000, 1016, 1000, 1992]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5080, 2000: 2400, 3000: 3000}),\n   [[5080, 12, 2400, 5096, 1000, 2392]]),\n  ('integer that looks like a moved address',\n   ([{'pc': 20, 'slots': [2000, 1000, 3005]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5080, 2000: 2400, 3000: 3000}),\n   [[2000, 5080, 3005]]),\n  ('derived pointer below its base',\n   ([{'pc': 30, 'slots': [None, 2000, 1985]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5080, 2000: 2400, 3000: 3000}),\n   [[None, 2400, 2385]]),\n  ('several frames',\n   ([{'pc': 20, 'slots': [5, 2000, 9]}, {'pc': 30, 'slots': [1000, 3000, 3009]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5080, 2000: 2400, 3000: 3000}),\n   [[5, 2400, 9], [5080, 3000, 3009]]),\n  ('missing stack map',\n   ([{'pc': 20, 'slots': [1, 2, 3]}, {'pc': 16, 'slots': []}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5080, 2000: 2400, 3000: 3000}),\n   ['no-stackmap', 16]),\n  ('control: null reference slots',\n   ([{'pc': 20, 'slots': [5, None, 0]}],\n    {10: {'derived': [[3, 0], [5, 2]], 'refs': 5},\n     20: {'derived': [], 'refs': 2},\n     30: {'derived': [[2, 1]], 'refs': 3}},\n    {1000: 5080, 2000: 2400, 3000: 3000}),\n   [[5, None, 0]])]]\nfor label, args, expected in cases[N - 1]:\n    check(label, solve(*args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":"A deterministic, bounded teaching model of one garbage-collector mechanism with stipulated rules; it is not a production collector and claims no conformance to any particular runtime. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"w2-garbage-collector-invariants-stack-map-relocation-derived-base-value","generated_at":"2026-09-29T14:51:28.357418+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Precise collectors rely on stack maps; misreading them corrupts registers or keeps stale pointers.","root_cause":"The derived computation reads the base slot after it has been relocated.","sha256":"02e564c69386712e169814e7a43f172a5836bc3ef42f977483fc5fb5bb89b385","title":"Stack maps: derived pointers rebased on the already-relocated base · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":40.894,"exit_code":1,"observations":[{"actual":[[5016,8,2400,1016,1000,1992]],"check":"regression: references, integers and derived pointers","expected":[[5016,8,2400,5032,1000,2392]],"passed":false},{"actual":[[2000,5016,3001]],"check":"integer that looks like a moved address","expected":[[2000,5016,3001]],"passed":true},{"actual":[[null,2400,1989]],"check":"derived pointer below its base","expected":[[null,2400,2389]],"passed":false},{"actual":[[5,2400,9],[5016,3000,3005]],"check":"several frames","expected":[[5,2400,9],[5016,3000,3005]],"passed":true},{"actual":["no-stackmap",12],"check":"missing stack map","expected":["no-stackmap",12],"passed":true},{"actual":[[1,null,0]],"check":"control: null reference slots","expected":[[1,null,0]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"regression: references, integers and derived pointers\", \"actual\": [[5016, 8, 2400, 1016, 1000, 1992]], \"expected\": [[5016, 8, 2400, 5032, 1000, 2392]], \"passed\": false}, {\"check\": \"integer that looks like a moved address\", \"actual\": [[2000, 5016, 3001]], \"expected\": [[2000, 5016, 3001]], \"passed\": true}, {\"check\": \"derived pointer below its base\", \"actual\": [[null, 2400, 1989]], \"expected\": [[null, 2400, 2389]], \"passed\": false}, {\"check\": \"several frames\", \"actual\": [[5, 2400, 9], [5016, 3000, 3005]], \"expected\": [[5, 2400, 9], [5016, 3000, 3005]], \"passed\": true}, {\"check\": \"missing stack map\", \"actual\": [\"no-stackmap\", 12], \"expected\": [\"no-stackmap\", 12], \"passed\": true}, {\"check\": \"control: null reference slots\", \"actual\": [[1, null, 0]], \"expected\": [[1, null, 0]], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.543,"exit_code":1,"observations":[{"actual":[[5016,8,2400,1016,1000,1992]],"check":"regression: references, integers and derived pointers","expected":[[5016,8,2400,5032,1000,2392]],"passed":false},{"actual":[[2000,5016,3001]],"check":"integer that looks like a moved address","expected":[[2000,5016,3001]],"passed":true},{"actual":[[null,2400,1989]],"check":"derived pointer below its base","expected":[[null,2400,2389]],"passed":false},{"actual":[[5,2400,9],[5016,3000,3005]],"check":"several frames","expected":[[5,2400,9],[5016,3000,3005]],"passed":true},{"actual":["no-stackmap",12],"check":"missing stack map","expected":["no-stackmap",12],"passed":true},{"actual":[[1,null,0]],"check":"control: null reference slots","expected":[[1,null,0]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"regression: references, integers and derived pointers\", \"actual\": [[5016, 8, 2400, 1016, 1000, 1992]], \"expected\": [[5016, 8, 2400, 5032, 1000, 2392]], \"passed\": false}, {\"check\": \"integer that looks like a moved address\", \"actual\": [[2000, 5016, 3001]], \"expected\": [[2000, 5016, 3001]], \"passed\": true}, {\"check\": \"derived pointer below its base\", \"actual\": [[null, 2400, 1989]], \"expected\": [[null, 2400, 2389]], \"passed\": false}, {\"check\": \"several frames\", \"actual\": [[5, 2400, 9], [5016, 3000, 3005]], \"expected\": [[5, 2400, 9], [5016, 3000, 3005]], \"passed\": true}, {\"check\": \"missing stack map\", \"actual\": [\"no-stackmap\", 12], \"expected\": [\"no-stackmap\", 12], \"passed\": true}, {\"check\": \"control: null reference slots\", \"actual\": [[1, null, 0]], \"expected\": [[1, null, 0]], \"passed\": true}], \"passed\": false}\n"}},"member_only":{"stages":["fixed"],"fields":["implementations.fixed","verification.fixed","harness","repair"],"note":"The verified repair, its recorded checks, the repair description, and the scoring harness are available to members."}}