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FA-46781 / Bounded deques / Open access

Graceful deque close wakes consumers before buffered items drain · case 01

Graceful deque close wakes consumers before buffered items drain.

Verified by executionVariant 1 · 9 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Graceful deque close wakes consumers before buffered items drain.

THE FAILURE

Graceful deque close wakes consumers before buffered items drain.

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

Case contract

Graceful close forbids future insertion but permits draining buffered values. Empty closed deque reports closed rather than empty. Terminal consumer waiters wake exactly on first empty close or final drain.

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,closed,op,value,cap,waiters=x
    if op=='close':
        wakes=waiters if not closed else []
        return [a,True,None,wakes,not closed]
    if op=='push':
        if closed or len(a)==cap:return [a,closed,None,[],False]
        return [a+[value],closed,None,[],True]
    if not a:return [a,closed,'closed' if closed else 'empty',[],False]
    result=a[1:]
    wakes=waiters if closed and not result else []
    return [result,closed,a[0],wakes,True]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([[N],False,"close",0,3,[1,2]]), {1: [[1], True, None, [], True], 2: [[2], True, None, [], True], 3: [[3], True, None, [], True], 4: [[4], True, None, [], True], 5: [[5], True, None, [], True]}[N])
check('1', solve([[],False,"close",0,3,[1,2]]), {1: [[], True, None, [1, 2], True], 2: [[], True, None, [1, 2], True], 3: [[], True, None, [1, 2], True], 4: [[], True, None, [1, 2], True], 5: [[], True, None, [1, 2], True]}[N])
check('2', solve([[],True,"close",0,3,[1,2]]), {1: [[], True, None, [], False], 2: [[], True, None, [], False], 3: [[], True, None, [], False], 4: [[], True, None, [], False], 5: [[], True, None, [], False]}[N])
check('3', solve([[N],True,"push",N+1,3,[1]]), {1: [[1], True, None, [], False], 2: [[2], True, None, [], False], 3: [[3], True, None, [], False], 4: [[4], True, None, [], False], 5: [[5], True, None, [], False]}[N])
check('4', solve([[N,N+1],True,"pop",0,3,[1]]), {1: [[2], True, 1, [], True], 2: [[3], True, 2, [], True], 3: [[4], True, 3, [], True], 4: [[5], True, 4, [], True], 5: [[6], True, 5, [], True]}[N])
check('5', solve([[N],True,"pop",0,3,[1,2]]), {1: [[], True, 1, [1, 2], True], 2: [[], True, 2, [1, 2], True], 3: [[], True, 3, [1, 2], True], 4: [[], True, 4, [1, 2], True], 5: [[], True, 5, [1, 2], True]}[N])
check('6', solve([[],True,"pop",0,3,[1]]), {1: [[], True, 'closed', [], False], 2: [[], True, 'closed', [], False], 3: [[], True, 'closed', [], False], 4: [[], True, 'closed', [], False], 5: [[], True, 'closed', [], False]}[N])
check('7', solve([[],False,"pop",0,3,[1]]), {1: [[], False, 'empty', [], False], 2: [[], False, 'empty', [], False], 3: [[], False, 'empty', [], False], 4: [[], False, 'empty', [], False], 5: [[], False, 'empty', [], False]}[N])
check('8', solve([[N],False,"push",N+1,3,[]]), {1: [[1, 2], False, None, [], True], 2: [[2, 3], False, None, [], True], 3: [[3, 4], False, None, [], True], 4: [[4, 5], False, None, [], True], 5: [[5, 6], False, None, [], True]}[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], True, None, [1, 2], True][[1], True, None, [], True]Failed
1[[], True, None, [1, 2], True][[], True, None, [1, 2], True]Passed
2[[], True, None, [], False][[], True, None, [], False]Passed
3[[1], True, None, [], False][[1], True, None, [], False]Passed
4[[2], True, 1, [], True][[2], True, 1, [], True]Passed
5[[], True, 1, [1, 2], True][[], True, 1, [1, 2], True]Passed
6[[], True, 'closed', [], False][[], True, 'closed', [], False]Passed
7[[], False, 'empty', [], False][[], False, 'empty', [], False]Passed
8[[1, 2], False, None, [], True][[1, 2], False, None, [], True]Passed

SHA-256 / 4b5f8f9fb21399b078b5649593849624cede27c056d6ae7cef6b56df78fb3e1b

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    a,closed,op,value,cap,waiters=x
    if op=='close':
        wakes=waiters if not closed and len(a)<=1 else []
        return [a,True,None,wakes,not closed]
    if op=='push':
        if closed or len(a)==cap:return [a,closed,None,[],False]
        return [a+[value],closed,None,[],True]
    if not a:return [a,closed,'closed' if closed else 'empty',[],False]
    result=a[1:]
    wakes=waiters if closed and not result else []
    return [result,closed,a[0],wakes,True]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([[N],False,"close",0,3,[1,2]]), {1: [[1], True, None, [], True], 2: [[2], True, None, [], True], 3: [[3], True, None, [], True], 4: [[4], True, None, [], True], 5: [[5], True, None, [], True]}[N])
check('1', solve([[],False,"close",0,3,[1,2]]), {1: [[], True, None, [1, 2], True], 2: [[], True, None, [1, 2], True], 3: [[], True, None, [1, 2], True], 4: [[], True, None, [1, 2], True], 5: [[], True, None, [1, 2], True]}[N])
check('2', solve([[],True,"close",0,3,[1,2]]), {1: [[], True, None, [], False], 2: [[], True, None, [], False], 3: [[], True, None, [], False], 4: [[], True, None, [], False], 5: [[], True, None, [], False]}[N])
check('3', solve([[N],True,"push",N+1,3,[1]]), {1: [[1], True, None, [], False], 2: [[2], True, None, [], False], 3: [[3], True, None, [], False], 4: [[4], True, None, [], False], 5: [[5], True, None, [], False]}[N])
check('4', solve([[N,N+1],True,"pop",0,3,[1]]), {1: [[2], True, 1, [], True], 2: [[3], True, 2, [], True], 3: [[4], True, 3, [], True], 4: [[5], True, 4, [], True], 5: [[6], True, 5, [], True]}[N])
check('5', solve([[N],True,"pop",0,3,[1,2]]), {1: [[], True, 1, [1, 2], True], 2: [[], True, 2, [1, 2], True], 3: [[], True, 3, [1, 2], True], 4: [[], True, 4, [1, 2], True], 5: [[], True, 5, [1, 2], True]}[N])
check('6', solve([[],True,"pop",0,3,[1]]), {1: [[], True, 'closed', [], False], 2: [[], True, 'closed', [], False], 3: [[], True, 'closed', [], False], 4: [[], True, 'closed', [], False], 5: [[], True, 'closed', [], False]}[N])
check('7', solve([[],False,"pop",0,3,[1]]), {1: [[], False, 'empty', [], False], 2: [[], False, 'empty', [], False], 3: [[], False, 'empty', [], False], 4: [[], False, 'empty', [], False], 5: [[], False, 'empty', [], False]}[N])
check('8', solve([[N],False,"push",N+1,3,[]]), {1: [[1, 2], False, None, [], True], 2: [[2, 3], False, None, [], True], 3: [[3, 4], False, None, [], True], 4: [[4, 5], False, None, [], True], 5: [[5, 6], False, None, [], True]}[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], True, None, [1, 2], True][[1], True, None, [], True]Failed
1[[], True, None, [1, 2], True][[], True, None, [1, 2], True]Passed
2[[], True, None, [], False][[], True, None, [], False]Passed
3[[1], True, None, [], False][[1], True, None, [], False]Passed
4[[2], True, 1, [], True][[2], True, 1, [], True]Passed
5[[], True, 1, [1, 2], True][[], True, 1, [1, 2], True]Passed
6[[], True, 'closed', [], False][[], True, 'closed', [], False]Passed
7[[], False, 'empty', [], False][[], False, 'empty', [], False]Passed
8[[1, 2], False, None, [], True][[1, 2], False, None, [], True]Passed

SHA-256 / c00515b525dc630817d7391c543e4a0c255840d0d11d93637219203ad3b86bf4

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 9 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 2026-09-29T14:44:35.646782+00:00.

Case digest / f4693a54b8bf46a911dfe06c72a14fa4a8f6152cefc6ff8a7b7887c5e112bb82