{"abstract":"Duplicated descriptors advance independent read positions.","category":"Filesystem semantics","checks":6,"contract":"Deterministic in-memory filesystem model. Two descriptors are duplicates of one open-file description at offset zero. Return text read by alternating descriptors for nonnegative requested lengths; EOF reads return empty text.","evaluation_group":"model-138544f22e60327d","failed_approach":"Synchronizing positions only after the first read still loses later interleavings.","family":"z-filesystems-dup-offset","id":"FA-11546","implementations":{"attempt":{"sha256":"65c5b223bb800bd6e8acbbaecb88ae506f24cdcb5ea3f959134f3e46f814c65c","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(text, lengths):\n    positions=[0,0]\n    out=[]\n    for i,k in enumerate(lengths):\n     d=i%2; p=positions[d]; out.append(text[p:p+k]); positions[d]+=len(out[-1])\n     if i==0: positions[1]=positions[0]\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ns='abcdef'+str(N)\ncheck('interleaved duplicate reads',solve(s,[1,1,1,1]),['a','b','c','d'])\ncheck('one read',solve(s,[2]),['ab'])\ncheck('zero length does not advance',solve(s,[0,2,1]),['','ab','c'])\ncheck('EOF clips count',solve(s,[100,1]),[s,''])\ncheck('empty file',solve('',[N,1]),['',''])\ncheck('no reads',solve(s,[]),[])\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":"94f5674aed72a2865dd4865ca0dae86aa970a1e4cdb7407a7a319e2b882953b5","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(text, lengths):\n    positions=[0,0]\n    out=[]\n    for i,k in enumerate(lengths):\n     d=i%2; p=positions[d]; out.append(text[p:p+k]); positions[d]+=len(out[-1])\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ns='abcdef'+str(N)\ncheck('interleaved duplicate reads',solve(s,[1,1,1,1]),['a','b','c','d'])\ncheck('one read',solve(s,[2]),['ab'])\ncheck('zero length does not advance',solve(s,[0,2,1]),['','ab','c'])\ncheck('EOF clips count',solve(s,[100,1]),[s,''])\ncheck('empty file',solve('',[N,1]),['',''])\ncheck('no reads',solve(s,[]),[])\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"},"fixed":{"sha256":"887c1824232cdfc64308ffe6a627059bb33c26b321e6f8d34a6b677a080f2047","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(text, lengths):\n    position=0\n    out=[]\n    for k in lengths:\n     part=text[position:position+k]; out.append(part); position+=len(part)\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ns='abcdef'+str(N)\ncheck('interleaved duplicate reads',solve(s,[1,1,1,1]),['a','b','c','d'])\ncheck('one read',solve(s,[2]),['ab'])\ncheck('zero length does not advance',solve(s,[0,2,1]),['','ab','c'])\ncheck('EOF clips count',solve(s,[100,1]),[s,''])\ncheck('empty file',solve('',[N,1]),['',''])\ncheck('no reads',solve(s,[]),[])\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":"z-filesystems-dup-offset","generated_at":"2026-09-29T14:38:48.884763+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"An offline semantic experiment for file API clients; it models only the stated operations, not a complete operating system.","repair":"Use one shared position for reads through either duplicated descriptor.","root_cause":"A duplicated descriptor is modeled as a fresh open-file description.","sha256":"ed9370828dff00c7b5ac0081fdabe76f2f183aa8e7009bfc74c1e14036e9ec65","title":"Duplicated descriptors advance independent read positions · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":39.701,"exit_code":1,"observations":[{"actual":["a","b","b","c"],"check":"interleaved duplicate reads","expected":["a","b","c","d"],"passed":false},{"actual":["ab"],"check":"one read","expected":["ab"],"passed":true},{"actual":["","ab","a"],"check":"zero length does not advance","expected":["","ab","c"],"passed":false},{"actual":["abcdef1",""],"check":"EOF clips count","expected":["abcdef1",""],"passed":true},{"actual":["",""],"check":"empty file","expected":["",""],"passed":true},{"actual":[],"check":"no reads","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"interleaved duplicate reads\", \"actual\": [\"a\", \"b\", \"b\", \"c\"], \"expected\": [\"a\", \"b\", \"c\", \"d\"], \"passed\": false}, {\"check\": \"one read\", \"actual\": [\"ab\"], \"expected\": [\"ab\"], \"passed\": true}, {\"check\": \"zero length does not advance\", \"actual\": [\"\", \"ab\", \"a\"], \"expected\": [\"\", \"ab\", \"c\"], \"passed\": false}, {\"check\": \"EOF clips count\", \"actual\": [\"abcdef1\", \"\"], \"expected\": [\"abcdef1\", \"\"], \"passed\": true}, {\"check\": \"empty file\", \"actual\": [\"\", \"\"], \"expected\": [\"\", \"\"], \"passed\": true}, {\"check\": \"no reads\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":37.406,"exit_code":1,"observations":[{"actual":["a","a","b","b"],"check":"interleaved duplicate reads","expected":["a","b","c","d"],"passed":false},{"actual":["ab"],"check":"one read","expected":["ab"],"passed":true},{"actual":["","ab","a"],"check":"zero length does not advance","expected":["","ab","c"],"passed":false},{"actual":["abcdef1","a"],"check":"EOF clips count","expected":["abcdef1",""],"passed":false},{"actual":["",""],"check":"empty file","expected":["",""],"passed":true},{"actual":[],"check":"no reads","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"interleaved duplicate reads\", \"actual\": [\"a\", \"a\", \"b\", \"b\"], \"expected\": [\"a\", \"b\", \"c\", \"d\"], \"passed\": false}, {\"check\": \"one read\", \"actual\": [\"ab\"], \"expected\": [\"ab\"], \"passed\": true}, {\"check\": \"zero length does not advance\", \"actual\": [\"\", \"ab\", \"a\"], \"expected\": [\"\", \"ab\", \"c\"], \"passed\": false}, {\"check\": \"EOF clips count\", \"actual\": [\"abcdef1\", \"a\"], \"expected\": [\"abcdef1\", \"\"], \"passed\": false}, {\"check\": \"empty file\", \"actual\": [\"\", \"\"], \"expected\": [\"\", \"\"], \"passed\": true}, {\"check\": \"no reads\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":39.583,"exit_code":0,"observations":[{"actual":["a","b","c","d"],"check":"interleaved duplicate reads","expected":["a","b","c","d"],"passed":true},{"actual":["ab"],"check":"one read","expected":["ab"],"passed":true},{"actual":["","ab","c"],"check":"zero length does not advance","expected":["","ab","c"],"passed":true},{"actual":["abcdef1",""],"check":"EOF clips count","expected":["abcdef1",""],"passed":true},{"actual":["",""],"check":"empty file","expected":["",""],"passed":true},{"actual":[],"check":"no reads","expected":[],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"interleaved duplicate reads\", \"actual\": [\"a\", \"b\", \"c\", \"d\"], \"expected\": [\"a\", \"b\", \"c\", \"d\"], \"passed\": true}, {\"check\": \"one read\", \"actual\": [\"ab\"], \"expected\": [\"ab\"], \"passed\": true}, {\"check\": \"zero length does not advance\", \"actual\": [\"\", \"ab\", \"c\"], \"expected\": [\"\", \"ab\", \"c\"], \"passed\": true}, {\"check\": \"EOF clips count\", \"actual\": [\"abcdef1\", \"\"], \"expected\": [\"abcdef1\", \"\"], \"passed\": true}, {\"check\": \"empty file\", \"actual\": [\"\", \"\"], \"expected\": [\"\", \"\"], \"passed\": true}, {\"check\": \"no reads\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}