{"abstract":"Infinite sign-extension bits leak into a finite-word complement.","category":"Integer arithmetic","checks":4,"contract":"Integer arguments; denominators, steps, moduli, and bit widths are positive. Unsigned word inputs fit the specified width except where masking is explicitly the operation. Sequence sizes are nonnegative. Fixed width bit complement. Exact operational definition: n ^ ((1<<bits)-1)","contract_signature":"n, bits","evaluation_group":"model-392db5467e61f0aa","failed_approach":"Taking a magnitude is not a finite-word mask.","family":"xn-fixed-width-bit-complement","id":"FA-5396","implementations":{"attempt":{"sha256":"5d91168db5ace3505648d1aec3c4ee2b4b5ff349d74829166e3c7f18960b4a53","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nimport calendar\nimport statistics\nimport itertools\nfrom fractions import Fraction\nfrom datetime import date, datetime, timedelta, timezone\nfrom decimal import Decimal, ROUND_HALF_UP, ROUND_DOWN, ROUND_CEILING, ROUND_FLOOR\n\nN = 1\nobservations = []\ndef solve(n, bits):\n    return abs(~n)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1: (0, 4)', solve(*(0, 4)), 15)\ncheck('fixture 2: (15, 4)', solve(*(15, 4)), 0)\ncheck('fixture 3: (5, 4)', solve(*(5, 4)), 10)\ncheck('fixture 4: (1, 1)', solve(*(1, 1)), 0)\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":"6049788a34b43d7d86b20d8d70ceddd0060e3a8f1d7ec470fe4ae223a2e55ba9","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nimport calendar\nimport statistics\nimport itertools\nfrom fractions import Fraction\nfrom datetime import date, datetime, timedelta, timezone\nfrom decimal import Decimal, ROUND_HALF_UP, ROUND_DOWN, ROUND_CEILING, ROUND_FLOOR\n\nN = 1\nobservations = []\ndef solve(n, bits):\n    return ~n\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1: (0, 4)', solve(*(0, 4)), 15)\ncheck('fixture 2: (15, 4)', solve(*(15, 4)), 0)\ncheck('fixture 3: (5, 4)', solve(*(5, 4)), 10)\ncheck('fixture 4: (1, 1)', solve(*(1, 1)), 0)\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":" 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":"xn-fixed-width-bit-complement","generated_at":"2026-09-29T14:37:49.082572+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Small exact fixtures expose this error without platform timing, external services, or probabilistic observations. Integer mathematics results depend on the stated convention.","root_cause":"Infinite sign-extension bits leak into a finite-word complement.","sha256":"b0488800c63bd8666caff041680baf90d72de2a8bcc1dcb006e152dcf99c8d79","title":"Fixed width bit complement · 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":47.006,"exit_code":1,"observations":[{"actual":1,"check":"fixture 1: (0, 4)","expected":15,"passed":false},{"actual":16,"check":"fixture 2: (15, 4)","expected":0,"passed":false},{"actual":6,"check":"fixture 3: (5, 4)","expected":10,"passed":false},{"actual":2,"check":"fixture 4: (1, 1)","expected":0,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: (0, 4)\", \"actual\": 1, \"expected\": 15, \"passed\": false}, {\"check\": \"fixture 2: (15, 4)\", \"actual\": 16, \"expected\": 0, \"passed\": false}, {\"check\": \"fixture 3: (5, 4)\", \"actual\": 6, \"expected\": 10, \"passed\": false}, {\"check\": \"fixture 4: (1, 1)\", \"actual\": 2, \"expected\": 0, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":127.619,"exit_code":1,"observations":[{"actual":-1,"check":"fixture 1: (0, 4)","expected":15,"passed":false},{"actual":-16,"check":"fixture 2: (15, 4)","expected":0,"passed":false},{"actual":-6,"check":"fixture 3: (5, 4)","expected":10,"passed":false},{"actual":-2,"check":"fixture 4: (1, 1)","expected":0,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: (0, 4)\", \"actual\": -1, \"expected\": 15, \"passed\": false}, {\"check\": \"fixture 2: (15, 4)\", \"actual\": -16, \"expected\": 0, \"passed\": false}, {\"check\": \"fixture 3: (5, 4)\", \"actual\": -6, \"expected\": 10, \"passed\": false}, {\"check\": \"fixture 4: (1, 1)\", \"actual\": -2, \"expected\": 0, \"passed\": false}], \"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."}}