FAILURE MAP
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FA-46946 / Bounded deques / Open access

Empty deque reservation commit invalidates all iterators · case 01

Empty deque reservation commit invalidates all iterators.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Empty deque reservation commit invalidates all iterators.

THE FAILURE

Empty deque reservation commit invalidates all iterators.

Unsuccessful approach: The partial repair still applies the incorrect transition to an admitted boundary or multi-element case.

Case contract

A bounded deque write reservation publishes exactly its initialized prefix. Reject negative, uninitialized, over-reserved or over-capacity commit counts atomically. Successful commit releases the entire reservation and advances structure epoch only for nonempty publication.

Why this case matters

Controlled bounded deque implementation model with explicit storage and lifecycle observations.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    a,reserved,values,written,cap,epoch=x
    if written<0 or written>len(values) or written>reserved:return [a,reserved,epoch,False,[]]
    if len(a)+written>cap:return [a,reserved,epoch,False,[]]
    published=values[:written]
    state=a+published
    remaining=0
    version=epoch+1
    unused=values[written:]
    return [state,remaining,version,True,unused]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([[N],3,[N+1,N+2,N+3],2,5,4]), {1: [[1, 2, 3], 0, 5, True, [4]], 2: [[2, 3, 4], 0, 5, True, [5]], 3: [[3, 4, 5], 0, 5, True, [6]], 4: [[4, 5, 6], 0, 5, True, [7]], 5: [[5, 6, 7], 0, 5, True, [8]]}[N])
check('1', solve([[N],1,[N+1,N+2],2,4,2]), {1: [[1], 1, 2, False, []], 2: [[2], 1, 2, False, []], 3: [[3], 1, 2, False, []], 4: [[4], 1, 2, False, []], 5: [[5], 1, 2, False, []]}[N])
check('2', solve([[N],3,[N+1],2,5,1]), {1: [[1], 3, 1, False, []], 2: [[2], 3, 1, False, []], 3: [[3], 3, 1, False, []], 4: [[4], 3, 1, False, []], 5: [[5], 3, 1, False, []]}[N])
check('3', solve([[N,N+1],2,[N+2,N+3],2,3,5]), {1: [[1, 2], 2, 5, False, []], 2: [[2, 3], 2, 5, False, []], 3: [[3, 4], 2, 5, False, []], 4: [[4, 5], 2, 5, False, []], 5: [[5, 6], 2, 5, False, []]}[N])
check('4', solve([[N],2,[N+1,N+2],0,4,7]), {1: [[1], 0, 7, True, [2, 3]], 2: [[2], 0, 7, True, [3, 4]], 3: [[3], 0, 7, True, [4, 5]], 4: [[4], 0, 7, True, [5, 6]], 5: [[5], 0, 7, True, [6, 7]]}[N])
check('5', solve([[],2,[N,N+1],2,2,0]), {1: [[1, 2], 0, 1, True, []], 2: [[2, 3], 0, 1, True, []], 3: [[3, 4], 0, 1, True, []], 4: [[4, 5], 0, 1, True, []], 5: [[5, 6], 0, 1, True, []]}[N])
check('6', solve([[N],2,[N+1],-1,4,1]), {1: [[1], 2, 1, False, []], 2: [[2], 2, 1, False, []], 3: [[3], 2, 1, False, []], 4: [[4], 2, 1, False, []], 5: [[5], 2, 1, False, []]}[N])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
0[[1, 2, 3], 0, 5, True, [4]][[1, 2, 3], 0, 5, True, [4]]Passed
1[[1], 1, 2, False, []][[1], 1, 2, False, []]Passed
2[[1], 3, 1, False, []][[1], 3, 1, False, []]Passed
3[[1, 2], 2, 5, False, []][[1, 2], 2, 5, False, []]Passed
4[[1], 0, 8, True, [2, 3]][[1], 0, 7, True, [2, 3]]Failed
5[[1, 2], 0, 1, True, []][[1, 2], 0, 1, True, []]Passed
6[[1], 2, 1, False, []][[1], 2, 1, False, []]Passed

SHA-256 / 64c2470deda08dd058b4a279da40ddb4f826e6b97bb56411eb7476b2e7c0ab39

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    a,reserved,values,written,cap,epoch=x
    if written<0 or written>len(values) or written>reserved:return [a,reserved,epoch,False,[]]
    if len(a)+written>cap:return [a,reserved,epoch,False,[]]
    published=values[:written]
    state=a+published
    remaining=0
    version=epoch+1 if values else epoch
    unused=values[written:]
    return [state,remaining,version,True,unused]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([[N],3,[N+1,N+2,N+3],2,5,4]), {1: [[1, 2, 3], 0, 5, True, [4]], 2: [[2, 3, 4], 0, 5, True, [5]], 3: [[3, 4, 5], 0, 5, True, [6]], 4: [[4, 5, 6], 0, 5, True, [7]], 5: [[5, 6, 7], 0, 5, True, [8]]}[N])
check('1', solve([[N],1,[N+1,N+2],2,4,2]), {1: [[1], 1, 2, False, []], 2: [[2], 1, 2, False, []], 3: [[3], 1, 2, False, []], 4: [[4], 1, 2, False, []], 5: [[5], 1, 2, False, []]}[N])
check('2', solve([[N],3,[N+1],2,5,1]), {1: [[1], 3, 1, False, []], 2: [[2], 3, 1, False, []], 3: [[3], 3, 1, False, []], 4: [[4], 3, 1, False, []], 5: [[5], 3, 1, False, []]}[N])
check('3', solve([[N,N+1],2,[N+2,N+3],2,3,5]), {1: [[1, 2], 2, 5, False, []], 2: [[2, 3], 2, 5, False, []], 3: [[3, 4], 2, 5, False, []], 4: [[4, 5], 2, 5, False, []], 5: [[5, 6], 2, 5, False, []]}[N])
check('4', solve([[N],2,[N+1,N+2],0,4,7]), {1: [[1], 0, 7, True, [2, 3]], 2: [[2], 0, 7, True, [3, 4]], 3: [[3], 0, 7, True, [4, 5]], 4: [[4], 0, 7, True, [5, 6]], 5: [[5], 0, 7, True, [6, 7]]}[N])
check('5', solve([[],2,[N,N+1],2,2,0]), {1: [[1, 2], 0, 1, True, []], 2: [[2, 3], 0, 1, True, []], 3: [[3, 4], 0, 1, True, []], 4: [[4, 5], 0, 1, True, []], 5: [[5, 6], 0, 1, True, []]}[N])
check('6', solve([[N],2,[N+1],-1,4,1]), {1: [[1], 2, 1, False, []], 2: [[2], 2, 1, False, []], 3: [[3], 2, 1, False, []], 4: [[4], 2, 1, False, []], 5: [[5], 2, 1, False, []]}[N])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
0[[1, 2, 3], 0, 5, True, [4]][[1, 2, 3], 0, 5, True, [4]]Passed
1[[1], 1, 2, False, []][[1], 1, 2, False, []]Passed
2[[1], 3, 1, False, []][[1], 3, 1, False, []]Passed
3[[1, 2], 2, 5, False, []][[1, 2], 2, 5, False, []]Passed
4[[1], 0, 8, True, [2, 3]][[1], 0, 7, True, [2, 3]]Failed
5[[1, 2], 0, 1, True, []][[1, 2], 0, 1, True, []]Passed
6[[1], 2, 1, False, []][[1], 2, 1, False, []]Passed

SHA-256 / b840e35ce885aa4eb9047dbee852ac234f20ff3f79c29966a4a1317dca9b01e9

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 7 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

Offline finite deterministic model; no claim of production implementation or concurrent memory-model conformance. 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.

Observations recorded using Python 3.12.14 at 2026-09-29T14:44:40.448254+00:00.

Case digest / 540372b888a7e64cf1a6ceb518a1162456dac17ed1bb507ef0b5e2caf5e20a33