FA-92336 / PLC ladder logic scan cycles / Open access

INT overflow bit stays set for later instructions · case 01

After one handled overflow every later math result is flagged, saturated and trapped.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The overflow bit is ORed with its previous value instead of recomputed per instruction.

VERIFIED REPAIR

Recompute V from each instruction's own result.

Unsuccessful approach: Clearing the sticky bit only on scans with clear set still carries it into the next scan.

Case contract

16-bit INT math rung followed by a later fault-clearing rung, one op per scan; ops is a list of [a, b, ADD|SUB|MUL, clear]. A result outside -32768..32767 sets the overflow bit V for that instruction and the overflow trap; the stored result is saturated to 32767/-32768 when clamp is set or wrapped as 16-bit two's complement otherwise. V is recomputed per instruction. The later rung clears the trap when clear is true; a trap still set at end of scan halts the processor. Return [result, V, trap] per scan, then "halted" and stop if faulted.

Why this case matters

Ladder programs are executed as repeated scans; each defect here changes what a rung, timer, counter or data-table instruction reports on a particular scan, which is how commissioning and field faults are actually observed.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(clamp, ops):
    trap = False
    last_v = False
    out = []
    for a, b, op, clear in ops:
        if op == 'ADD':
            r = a + b
        elif op == 'SUB':
            r = a - b
        else:
            r = a * b
        v = last_v or not (-32768 <= r <= 32767)
        last_v = v
        if v:
            trap = True
            if clamp:
                r = 32767 if r > 0 else -32768
            else:
                r = (r + 32768) % 65536 - 32768
        if clear:
            trap = False
        out.append([r, v, trap])
        if trap:
            out.append('halted')
            break
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: saturation both signs',
   [True,
    [[-2, -20000, 'MUL', True],
     [-20000, 20000, 'SUB', True],
     [32767, 0, 'ADD', False],
     [1, 1, 'ADD', False]]],
   [[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]],
  ['regression: overflow then clean ops',
   [True, [[32767, 1, 'ADD', True], [5, 5, 'ADD', False], [7, 7, 'SUB', False]]],
   [[32767, True, False], [10, False, False], [0, False, False]]],
  ['control: wrap with cleared traps',
   [False,
    [[30000, 5000, 'ADD', True],
     [-30000, 5000, 'SUB', True],
     [200, 200, 'MUL', False],
     [1, 1, 'ADD', False]]],
   [[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']],
  ['control: exact limits',
   [False, [[-32767, 1, 'SUB', False], [32766, 1, 'ADD', False], [3, 4, 'MUL', False]]],
   [[-32768, False, False], [32767, False, False], [12, False, False]]],
  ['regression: scenario 1',
   [False,
    [[-32768, -20192, 'SUB', True],
     [12968, -30310, 'ADD', False],
     [-31305, 2, 'SUB', False],
     [11091, 200, 'MUL', True],
     [10310, 200, 'SUB', False]]],
   [[-12576, False, False],
    [-17342, False, False],
    [-31307, False, False],
    [-10024, True, False],
    [10110, False, False]]],
  ['control: scenario 2',
   [True,
    [[27834, -6307, 'SUB', False],
     [30000, -15473, 'SUB', False],
     [-1, 1, 'MUL', False],
     [-30000, -4507, 'SUB', True],
     [-21177, 21481, 'MUL', False],
     [31159, 1, 'SUB', False]]],
   [[32767, True, True], 'halted']],
  ['control: scenario 3',
   [False,
    [[18788, 200, 'SUB', True],
     [20369, -23104, 'MUL', False],
     [-32768, 10449, 'ADD', False],
     [-17550, 18799, 'ADD', False],
     [1, 32767, 'MUL', False]]],
   [[18588, False, False], [8640, True, True], 'halted']],
  ['control: scenario 4',
   [False,
    [[30000, 1, 'ADD', True],
     [-20338, 30000, 'ADD', True],
     [18879, 1, 'SUB', True],
     [27305, -32768, 'MUL', True],
     [16107, -9800, 'MUL', False],
     [3999, -32768, 'SUB', False],
     [1, -21623, 'ADD', False]]],
   [[30001, False, False],
    [9662, False, False],
    [18878, False, False],
    [-32768, True, False],
    [27624, True, True],
    'halted']]],
 [['regression: overflow then clean ops',
   [True, [[32767, 1, 'ADD', True], [5, 5, 'ADD', False], [7, 7, 'SUB', False]]],
   [[32767, True, False], [10, False, False], [0, False, False]]],
  ['regression: scenario 3',
   [False,
    [[-10436, -32034, 'MUL', True],
     [2, 22108, 'SUB', False],
     [7659, 2, 'MUL', False],
     [5339, 1, 'MUL', False]]],
   [[7688, True, False], [-22106, False, False], [15318, False, False], [5339, False, False]]],
  ['control: wrap with cleared traps',
   [False,
    [[30000, 5000, 'ADD', True],
     [-30000, 5000, 'SUB', True],
     [200, 200, 'MUL', False],
     [1, 1, 'ADD', False]]],
   [[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']],
  ['regression: saturation both signs',
   [True,
    [[-2, -20000, 'MUL', True],
     [-20000, 20000, 'SUB', True],
     [32767, 0, 'ADD', False],
     [1, 1, 'ADD', False]]],
   [[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]],
  ['control: exact limits',
   [False, [[-32767, 1, 'SUB', False], [32766, 1, 'ADD', False], [3, 4, 'MUL', False]]],
   [[-32768, False, False], [32767, False, False], [12, False, False]]],
  ['control: scenario 1',
   [False,
    [[-15041, -14459, 'SUB', False],
     [13071, -30000, 'ADD', True],
     [-17526, -1, 'MUL', True],
     [-30000, 200, 'MUL', False]]],
   [[-582, False, False], [-16929, False, False], [17526, False, False], [29312, True, True], 'halted']],
  ['control: scenario 2',
   [True,
    [[-1048, 30000, 'ADD', False],
     [2, -13120, 'SUB', False],
     [29306, -32768, 'SUB', True],
     [-9919, -24931, 'MUL', True]]],
   [[28952, False, False], [13122, False, False], [32767, True, False], [32767, True, False]]],
  ['regression: scenario 4',
   [False,
    [[200, -21485, 'MUL', True],
     [-200, -32768, 'SUB', True],
     [15677, 32607, 'ADD', True],
     [-10557, 26430, 'SUB', False],
     [-200, 30000, 'SUB', True],
     [-30000, 200, 'ADD', True],
     [26687, -20358, 'ADD', False]]],
   [[28376, True, False], [32568, False, False], [-17252, True, False], [28549, True, True], 'halted']]],
 [['regression: scenario 8',
   [False,
    [[-4887, -27663, 'SUB', True],
     [30000, 6920, 'MUL', True],
     [28114, 1, 'SUB', False],
     [1, -5974, 'SUB', False]]],
   [[22776, False, False], [-18048, True, False], [28113, False, False], [5975, False, False]]],
  ['regression: scenario 12',
   [True,
    [[-200, -14943, 'ADD', True],
     [2, 30000, 'SUB', True],
     [2, -32768, 'SUB', True],
     [24257, -25508, 'SUB', True],
     [932, -29592, 'SUB', False],
     [-32768, -15582, 'ADD', False],
     [25886, -200, 'SUB', False],
     [15203, -12133, 'SUB', False]]],
   [[-15143, False, False],
    [-29998, False, False],
    [32767, True, False],
    [32767, True, False],
    [30524, False, False],
    [-32768, True, True],
    'halted']],
  ['control: wrap with cleared traps',
   [False,
    [[30000, 5000, 'ADD', True],
     [-30000, 5000, 'SUB', True],
     [200, 200, 'MUL', False],
     [1, 1, 'ADD', False]]],
   [[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']],
  ['regression: saturation both signs',
   [True,
    [[-2, -20000, 'MUL', True],
     [-20000, 20000, 'SUB', True],
     [32767, 0, 'ADD', False],
     [1, 1, 'ADD', False]]],
   [[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]],
  ['control: exact limits',
   [False, [[-32767, 1, 'SUB', False], [32766, 1, 'ADD', False], [3, 4, 'MUL', False]]],
   [[-32768, False, False], [32767, False, False], [12, False, False]]],
  ['regression: overflow then clean ops',
   [True, [[32767, 1, 'ADD', True], [5, 5, 'ADD', False], [7, 7, 'SUB', False]]],
   [[32767, True, False], [10, False, False], [0, False, False]]],
  ['control: scenario 1',
   [False,
    [[15094, -24454, 'MUL', False],
     [-30000, 24363, 'MUL', True],
     [2, -14871, 'MUL', False],
     [1, -26550, 'MUL', True],
     [-1, -7090, 'SUB', False],
     [32767, 1, 'MUL', True],
     [-32768, 15967, 'ADD', False],
     [21457, -28729, 'SUB', True]]],
   [[-9924, True, True], 'halted']],
  ['control: scenario 2',
   [False,
    [[-200, -200, 'ADD', True],
     [32767, 200, 'MUL', False],
     [-9390, 1, 'MUL', False],
     [-11169, -28064, 'ADD', True],
     [22720, -1, 'ADD', False],
     [-200, -1, 'ADD', False],
     [-12859, 1, 'ADD', True]]],
   [[-400, False, False], [-200, True, True], 'halted']]],
 [['regression: scenario 3',
   [False,
    [[-32768, 19187, 'MUL', True],
     [-7301, -200, 'SUB', False],
     [-32768, 30000, 'SUB', True],
     [-9747, -24186, 'ADD', True],
     [-1, -22920, 'SUB', True],
     [-259, 22293, 'SUB', False],
     [23494, -1, 'MUL', False],
     [-32529, 24353, 'SUB', True]]],
   [[-32768, True, False],
    [-7101, False, False],
    [2768, True, False],
    [31603, True, False],
    [22919, False, False],
    [-22552, False, False],
    [-23494, False, False],
    [8654, True, False]]],
  ['regression: scenario 31',
   [True,
    [[-2900, -200, 'MUL', True],
     [23750, 200, 'SUB', False],
     [200, -31152, 'MUL', True],
     [30000, -32768, 'SUB', True]]],
   [[32767, True, False], [23550, False, False], [-32768, True, False], [32767, True, False]]],
  ['control: wrap with cleared traps',
   [False,
    [[30000, 5000, 'ADD', True],
     [-30000, 5000, 'SUB', True],
     [200, 200, 'MUL', False],
     [1, 1, 'ADD', False]]],
   [[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']],
  ['regression: saturation both signs',
   [True,
    [[-2, -20000, 'MUL', True],
     [-20000, 20000, 'SUB', True],
     [32767, 0, 'ADD', False],
     [1, 1, 'ADD', False]]],
   [[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]],
  ['control: exact limits',
   [False, [[-32767, 1, 'SUB', False], [32766, 1, 'ADD', False], [3, 4, 'MUL', False]]],
   [[-32768, False, False], [32767, False, False], [12, False, False]]],
  ['regression: overflow then clean ops',
   [True, [[32767, 1, 'ADD', True], [5, 5, 'ADD', False], [7, 7, 'SUB', False]]],
   [[32767, True, False], [10, False, False], [0, False, False]]],
  ['control: scenario 1',
   [False,
    [[-26759, 2, 'SUB', True],
     [-30000, -32768, 'SUB', False],
     [-3730, -31438, 'ADD', False],
     [200, 200, 'SUB', True],
     [-24761, 200, 'SUB', True],
     [-20747, 200, 'SUB', False],
     [200, 19789, 'SUB', True]]],
   [[-26761, False, False], [2768, False, False], [30368, True, True], 'halted']],
  ['regression: scenario 2',
   [False,
    [[30000, -32768, 'ADD', True],
     [4451, 31437, 'SUB', False],
     [-1, 22093, 'MUL', False],
     [-30000, -18488, 'SUB', False],
     [30000, -28921, 'MUL', True],
     [-200, 23349, 'ADD', True],
     [-32768, 200, 'SUB', False]]],
   [[-2768, False, False],
    [-26986, False, False],
    [-22093, False, False],
    [-11512, False, False],
    [1104, True, False],
    [23149, False, False],
    [32568, True, True],
    'halted']]],
 [['regression: scenario 13',
   [False,
    [[-30088, 16833, 'SUB', True],
     [1555, 200, 'ADD', False],
     [200, -31213, 'SUB', True],
     [-10659, -15907, 'MUL', False],
     [2, -10563, 'ADD', True],
     [-9064, 16082, 'ADD', True],
     [30646, -1, 'ADD', True],
     [10428, 200, 'ADD', True]]],
   [[18615, True, False], [1755, False, False], [31413, False, False], [11081, True, True], 'halted']],
  ['regression: scenario 18',
   [True,
    [[-24623, 2, 'MUL', True],
     [-200, -32768, 'MUL', True],
     [1, -1, 'SUB', False],
     [-22404, -5569, 'SUB', True],
     [30526, 30000, 'MUL', True]]],
   [[-32768, True, False],
    [32767, True, False],
    [2, False, False],
    [-16835, False, False],
    [32767, True, False]]],
  ['control: wrap with cleared traps',
   [False,
    [[30000, 5000, 'ADD', True],
     [-30000, 5000, 'SUB', True],
     [200, 200, 'MUL', False],
     [1, 1, 'ADD', False]]],
   [[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']],
  ['regression: saturation both signs',
   [True,
    [[-2, -20000, 'MUL', True],
     [-20000, 20000, 'SUB', True],
     [32767, 0, 'ADD', False],
     [1, 1, 'ADD', False]]],
   [[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]],
  ['control: exact limits',
   [False, [[-32767, 1, 'SUB', False], [32766, 1, 'ADD', False], [3, 4, 'MUL', False]]],
   [[-32768, False, False], [32767, False, False], [12, False, False]]],
  ['regression: overflow then clean ops',
   [True, [[32767, 1, 'ADD', True], [5, 5, 'ADD', False], [7, 7, 'SUB', False]]],
   [[32767, True, False], [10, False, False], [0, False, False]]],
  ['control: scenario 1',
   [True,
    [[160, 2, 'SUB', True], [200, 200, 'SUB', True], [222, 200, 'SUB', False], [200, -32768, 'ADD', True]]],
   [[158, False, False], [0, False, False], [22, False, False], [-32568, False, False]]],
  ['control: scenario 2',
   [True,
    [[30000, 1574, 'SUB', True],
     [-783, -29319, 'SUB', True],
     [2, 1803, 'SUB', False],
     [200, 2, 'ADD', True],
     [9942, 32767, 'MUL', True],
     [-30000, -19084, 'MUL', True],
     [-10106, -30460, 'ADD', False],
     [2, 32767, 'ADD', True]]],
   [[28426, False, False],
    [28536, False, False],
    [-1801, False, False],
    [202, False, False],
    [32767, True, False],
    [32767, True, False],
    [-32768, True, True],
    'halted']]]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
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 fixture	Actual	Expected	Outcome
regression: saturation both signs	`[[32767, True, False], [-32768, True, False], [32767, True, True], 'halted']`	`[[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]`	Failed
regression: overflow then clean ops	`[[32767, True, False], [32767, True, True], 'halted']`	`[[32767, True, False], [10, False, False], [0, False, False]]`	Failed
control: wrap with cleared traps	`[[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']`	`[[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']`	Passed
control: exact limits	`[[-32768, False, False], [32767, False, False], [12, False, False]]`	`[[-32768, False, False], [32767, False, False], [12, False, False]]`	Passed
regression: scenario 1	`[[-12576, False, False], [-17342, False, False], [-31307, False, False], [-10024, True, False], [10110, True, True], 'halted']`	`[[-12576, False, False], [-17342, False, False], [-31307, False, False], [-10024, True, False], [10110, False, False]]`	Failed
control: scenario 2	`[[32767, True, True], 'halted']`	`[[32767, True, True], 'halted']`	Passed
control: scenario 3	`[[18588, False, False], [8640, True, True], 'halted']`	`[[18588, False, False], [8640, True, True], 'halted']`	Passed
control: scenario 4	`[[30001, False, False], [9662, False, False], [18878, False, False], [-32768, True, False], [27624, True, True], 'halted']`	`[[30001, False, False], [9662, False, False], [18878, False, False], [-32768, True, False], [27624, True, True], 'halted']`	Passed

SHA-256 / 7fd307d399ab0ce36909371241723504438ab09d9f77005596e3d89979c64457

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(clamp, ops):
    trap = False
    last_v = False
    out = []
    for a, b, op, clear in ops:
        if op == 'ADD':
            r = a + b
        elif op == 'SUB':
            r = a - b
        else:
            r = a * b
        v = (last_v and not clear) or not (-32768 <= r <= 32767)
        last_v = v
        if v:
            trap = True
            if clamp:
                r = 32767 if r > 0 else -32768
            else:
                r = (r + 32768) % 65536 - 32768
        if clear:
            trap = False
        out.append([r, v, trap])
        if trap:
            out.append('halted')
            break
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: saturation both signs',
   [True,
    [[-2, -20000, 'MUL', True],
     [-20000, 20000, 'SUB', True],
     [32767, 0, 'ADD', False],
     [1, 1, 'ADD', False]]],
   [[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]],
  ['regression: overflow then clean ops',
   [True, [[32767, 1, 'ADD', True], [5, 5, 'ADD', False], [7, 7, 'SUB', False]]],
   [[32767, True, False], [10, False, False], [0, False, False]]],
  ['control: wrap with cleared traps',
   [False,
    [[30000, 5000, 'ADD', True],
     [-30000, 5000, 'SUB', True],
     [200, 200, 'MUL', False],
     [1, 1, 'ADD', False]]],
   [[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']],
  ['control: exact limits',
   [False, [[-32767, 1, 'SUB', False], [32766, 1, 'ADD', False], [3, 4, 'MUL', False]]],
   [[-32768, False, False], [32767, False, False], [12, False, False]]],
  ['regression: scenario 1',
   [False,
    [[-32768, -20192, 'SUB', True],
     [12968, -30310, 'ADD', False],
     [-31305, 2, 'SUB', False],
     [11091, 200, 'MUL', True],
     [10310, 200, 'SUB', False]]],
   [[-12576, False, False],
    [-17342, False, False],
    [-31307, False, False],
    [-10024, True, False],
    [10110, False, False]]],
  ['control: scenario 2',
   [True,
    [[27834, -6307, 'SUB', False],
     [30000, -15473, 'SUB', False],
     [-1, 1, 'MUL', False],
     [-30000, -4507, 'SUB', True],
     [-21177, 21481, 'MUL', False],
     [31159, 1, 'SUB', False]]],
   [[32767, True, True], 'halted']],
  ['control: scenario 3',
   [False,
    [[18788, 200, 'SUB', True],
     [20369, -23104, 'MUL', False],
     [-32768, 10449, 'ADD', False],
     [-17550, 18799, 'ADD', False],
     [1, 32767, 'MUL', False]]],
   [[18588, False, False], [8640, True, True], 'halted']],
  ['control: scenario 4',
   [False,
    [[30000, 1, 'ADD', True],
     [-20338, 30000, 'ADD', True],
     [18879, 1, 'SUB', True],
     [27305, -32768, 'MUL', True],
     [16107, -9800, 'MUL', False],
     [3999, -32768, 'SUB', False],
     [1, -21623, 'ADD', False]]],
   [[30001, False, False],
    [9662, False, False],
    [18878, False, False],
    [-32768, True, False],
    [27624, True, True],
    'halted']]],
 [['regression: overflow then clean ops',
   [True, [[32767, 1, 'ADD', True], [5, 5, 'ADD', False], [7, 7, 'SUB', False]]],
   [[32767, True, False], [10, False, False], [0, False, False]]],
  ['regression: scenario 3',
   [False,
    [[-10436, -32034, 'MUL', True],
     [2, 22108, 'SUB', False],
     [7659, 2, 'MUL', False],
     [5339, 1, 'MUL', False]]],
   [[7688, True, False], [-22106, False, False], [15318, False, False], [5339, False, False]]],
  ['control: wrap with cleared traps',
   [False,
    [[30000, 5000, 'ADD', True],
     [-30000, 5000, 'SUB', True],
     [200, 200, 'MUL', False],
     [1, 1, 'ADD', False]]],
   [[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']],
  ['regression: saturation both signs',
   [True,
    [[-2, -20000, 'MUL', True],
     [-20000, 20000, 'SUB', True],
     [32767, 0, 'ADD', False],
     [1, 1, 'ADD', False]]],
   [[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]],
  ['control: exact limits',
   [False, [[-32767, 1, 'SUB', False], [32766, 1, 'ADD', False], [3, 4, 'MUL', False]]],
   [[-32768, False, False], [32767, False, False], [12, False, False]]],
  ['control: scenario 1',
   [False,
    [[-15041, -14459, 'SUB', False],
     [13071, -30000, 'ADD', True],
     [-17526, -1, 'MUL', True],
     [-30000, 200, 'MUL', False]]],
   [[-582, False, False], [-16929, False, False], [17526, False, False], [29312, True, True], 'halted']],
  ['control: scenario 2',
   [True,
    [[-1048, 30000, 'ADD', False],
     [2, -13120, 'SUB', False],
     [29306, -32768, 'SUB', True],
     [-9919, -24931, 'MUL', True]]],
   [[28952, False, False], [13122, False, False], [32767, True, False], [32767, True, False]]],
  ['regression: scenario 4',
   [False,
    [[200, -21485, 'MUL', True],
     [-200, -32768, 'SUB', True],
     [15677, 32607, 'ADD', True],
     [-10557, 26430, 'SUB', False],
     [-200, 30000, 'SUB', True],
     [-30000, 200, 'ADD', True],
     [26687, -20358, 'ADD', False]]],
   [[28376, True, False], [32568, False, False], [-17252, True, False], [28549, True, True], 'halted']]],
 [['regression: scenario 8',
   [False,
    [[-4887, -27663, 'SUB', True],
     [30000, 6920, 'MUL', True],
     [28114, 1, 'SUB', False],
     [1, -5974, 'SUB', False]]],
   [[22776, False, False], [-18048, True, False], [28113, False, False], [5975, False, False]]],
  ['regression: scenario 12',
   [True,
    [[-200, -14943, 'ADD', True],
     [2, 30000, 'SUB', True],
     [2, -32768, 'SUB', True],
     [24257, -25508, 'SUB', True],
     [932, -29592, 'SUB', False],
     [-32768, -15582, 'ADD', False],
     [25886, -200, 'SUB', False],
     [15203, -12133, 'SUB', False]]],
   [[-15143, False, False],
    [-29998, False, False],
    [32767, True, False],
    [32767, True, False],
    [30524, False, False],
    [-32768, True, True],
    'halted']],
  ['control: wrap with cleared traps',
   [False,
    [[30000, 5000, 'ADD', True],
     [-30000, 5000, 'SUB', True],
     [200, 200, 'MUL', False],
     [1, 1, 'ADD', False]]],
   [[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']],
  ['regression: saturation both signs',
   [True,
    [[-2, -20000, 'MUL', True],
     [-20000, 20000, 'SUB', True],
     [32767, 0, 'ADD', False],
     [1, 1, 'ADD', False]]],
   [[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]],
  ['control: exact limits',
   [False, [[-32767, 1, 'SUB', False], [32766, 1, 'ADD', False], [3, 4, 'MUL', False]]],
   [[-32768, False, False], [32767, False, False], [12, False, False]]],
  ['regression: overflow then clean ops',
   [True, [[32767, 1, 'ADD', True], [5, 5, 'ADD', False], [7, 7, 'SUB', False]]],
   [[32767, True, False], [10, False, False], [0, False, False]]],
  ['control: scenario 1',
   [False,
    [[15094, -24454, 'MUL', False],
     [-30000, 24363, 'MUL', True],
     [2, -14871, 'MUL', False],
     [1, -26550, 'MUL', True],
     [-1, -7090, 'SUB', False],
     [32767, 1, 'MUL', True],
     [-32768, 15967, 'ADD', False],
     [21457, -28729, 'SUB', True]]],
   [[-9924, True, True], 'halted']],
  ['control: scenario 2',
   [False,
    [[-200, -200, 'ADD', True],
     [32767, 200, 'MUL', False],
     [-9390, 1, 'MUL', False],
     [-11169, -28064, 'ADD', True],
     [22720, -1, 'ADD', False],
     [-200, -1, 'ADD', False],
     [-12859, 1, 'ADD', True]]],
   [[-400, False, False], [-200, True, True], 'halted']]],
 [['regression: scenario 3',
   [False,
    [[-32768, 19187, 'MUL', True],
     [-7301, -200, 'SUB', False],
     [-32768, 30000, 'SUB', True],
     [-9747, -24186, 'ADD', True],
     [-1, -22920, 'SUB', True],
     [-259, 22293, 'SUB', False],
     [23494, -1, 'MUL', False],
     [-32529, 24353, 'SUB', True]]],
   [[-32768, True, False],
    [-7101, False, False],
    [2768, True, False],
    [31603, True, False],
    [22919, False, False],
    [-22552, False, False],
    [-23494, False, False],
    [8654, True, False]]],
  ['regression: scenario 31',
   [True,
    [[-2900, -200, 'MUL', True],
     [23750, 200, 'SUB', False],
     [200, -31152, 'MUL', True],
     [30000, -32768, 'SUB', True]]],
   [[32767, True, False], [23550, False, False], [-32768, True, False], [32767, True, False]]],
  ['control: wrap with cleared traps',
   [False,
    [[30000, 5000, 'ADD', True],
     [-30000, 5000, 'SUB', True],
     [200, 200, 'MUL', False],
     [1, 1, 'ADD', False]]],
   [[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']],
  ['regression: saturation both signs',
   [True,
    [[-2, -20000, 'MUL', True],
     [-20000, 20000, 'SUB', True],
     [32767, 0, 'ADD', False],
     [1, 1, 'ADD', False]]],
   [[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]],
  ['control: exact limits',
   [False, [[-32767, 1, 'SUB', False], [32766, 1, 'ADD', False], [3, 4, 'MUL', False]]],
   [[-32768, False, False], [32767, False, False], [12, False, False]]],
  ['regression: overflow then clean ops',
   [True, [[32767, 1, 'ADD', True], [5, 5, 'ADD', False], [7, 7, 'SUB', False]]],
   [[32767, True, False], [10, False, False], [0, False, False]]],
  ['control: scenario 1',
   [False,
    [[-26759, 2, 'SUB', True],
     [-30000, -32768, 'SUB', False],
     [-3730, -31438, 'ADD', False],
     [200, 200, 'SUB', True],
     [-24761, 200, 'SUB', True],
     [-20747, 200, 'SUB', False],
     [200, 19789, 'SUB', True]]],
   [[-26761, False, False], [2768, False, False], [30368, True, True], 'halted']],
  ['regression: scenario 2',
   [False,
    [[30000, -32768, 'ADD', True],
     [4451, 31437, 'SUB', False],
     [-1, 22093, 'MUL', False],
     [-30000, -18488, 'SUB', False],
     [30000, -28921, 'MUL', True],
     [-200, 23349, 'ADD', True],
     [-32768, 200, 'SUB', False]]],
   [[-2768, False, False],
    [-26986, False, False],
    [-22093, False, False],
    [-11512, False, False],
    [1104, True, False],
    [23149, False, False],
    [32568, True, True],
    'halted']]],
 [['regression: scenario 13',
   [False,
    [[-30088, 16833, 'SUB', True],
     [1555, 200, 'ADD', False],
     [200, -31213, 'SUB', True],
     [-10659, -15907, 'MUL', False],
     [2, -10563, 'ADD', True],
     [-9064, 16082, 'ADD', True],
     [30646, -1, 'ADD', True],
     [10428, 200, 'ADD', True]]],
   [[18615, True, False], [1755, False, False], [31413, False, False], [11081, True, True], 'halted']],
  ['regression: scenario 18',
   [True,
    [[-24623, 2, 'MUL', True],
     [-200, -32768, 'MUL', True],
     [1, -1, 'SUB', False],
     [-22404, -5569, 'SUB', True],
     [30526, 30000, 'MUL', True]]],
   [[-32768, True, False],
    [32767, True, False],
    [2, False, False],
    [-16835, False, False],
    [32767, True, False]]],
  ['control: wrap with cleared traps',
   [False,
    [[30000, 5000, 'ADD', True],
     [-30000, 5000, 'SUB', True],
     [200, 200, 'MUL', False],
     [1, 1, 'ADD', False]]],
   [[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']],
  ['regression: saturation both signs',
   [True,
    [[-2, -20000, 'MUL', True],
     [-20000, 20000, 'SUB', True],
     [32767, 0, 'ADD', False],
     [1, 1, 'ADD', False]]],
   [[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]],
  ['control: exact limits',
   [False, [[-32767, 1, 'SUB', False], [32766, 1, 'ADD', False], [3, 4, 'MUL', False]]],
   [[-32768, False, False], [32767, False, False], [12, False, False]]],
  ['regression: overflow then clean ops',
   [True, [[32767, 1, 'ADD', True], [5, 5, 'ADD', False], [7, 7, 'SUB', False]]],
   [[32767, True, False], [10, False, False], [0, False, False]]],
  ['control: scenario 1',
   [True,
    [[160, 2, 'SUB', True], [200, 200, 'SUB', True], [222, 200, 'SUB', False], [200, -32768, 'ADD', True]]],
   [[158, False, False], [0, False, False], [22, False, False], [-32568, False, False]]],
  ['control: scenario 2',
   [True,
    [[30000, 1574, 'SUB', True],
     [-783, -29319, 'SUB', True],
     [2, 1803, 'SUB', False],
     [200, 2, 'ADD', True],
     [9942, 32767, 'MUL', True],
     [-30000, -19084, 'MUL', True],
     [-10106, -30460, 'ADD', False],
     [2, 32767, 'ADD', True]]],
   [[28426, False, False],
    [28536, False, False],
    [-1801, False, False],
    [202, False, False],
    [32767, True, False],
    [32767, True, False],
    [-32768, True, True],
    'halted']]]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
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 fixture	Actual	Expected	Outcome
regression: saturation both signs	`[[32767, True, False], [-32768, True, False], [32767, True, True], 'halted']`	`[[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]`	Failed
regression: overflow then clean ops	`[[32767, True, False], [32767, True, True], 'halted']`	`[[32767, True, False], [10, False, False], [0, False, False]]`	Failed
control: wrap with cleared traps	`[[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']`	`[[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']`	Passed
control: exact limits	`[[-32768, False, False], [32767, False, False], [12, False, False]]`	`[[-32768, False, False], [32767, False, False], [12, False, False]]`	Passed
regression: scenario 1	`[[-12576, False, False], [-17342, False, False], [-31307, False, False], [-10024, True, False], [10110, True, True], 'halted']`	`[[-12576, False, False], [-17342, False, False], [-31307, False, False], [-10024, True, False], [10110, False, False]]`	Failed
control: scenario 2	`[[32767, True, True], 'halted']`	`[[32767, True, True], 'halted']`	Passed
control: scenario 3	`[[18588, False, False], [8640, True, True], 'halted']`	`[[18588, False, False], [8640, True, True], 'halted']`	Passed
control: scenario 4	`[[30001, False, False], [9662, False, False], [18878, False, False], [-32768, True, False], [27624, True, True], 'halted']`	`[[30001, False, False], [9662, False, False], [18878, False, False], [-32768, True, False], [27624, True, True], 'halted']`	Passed

SHA-256 / d26a00acf537b11bf84fc8477f8cd4e62dab745d43d76d0816e24d09c66f5778

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(clamp, ops):
    trap = False
    out = []
    for a, b, op, clear in ops:
        if op == 'ADD':
            r = a + b
        elif op == 'SUB':
            r = a - b
        else:
            r = a * b
        v = not (-32768 <= r <= 32767)
        if v:
            trap = True
            if clamp:
                r = 32767 if r > 0 else -32768
            else:
                r = (r + 32768) % 65536 - 32768
        if clear:
            trap = False
        out.append([r, v, trap])
        if trap:
            out.append('halted')
            break
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: saturation both signs',
   [True,
    [[-2, -20000, 'MUL', True],
     [-20000, 20000, 'SUB', True],
     [32767, 0, 'ADD', False],
     [1, 1, 'ADD', False]]],
   [[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]],
  ['regression: overflow then clean ops',
   [True, [[32767, 1, 'ADD', True], [5, 5, 'ADD', False], [7, 7, 'SUB', False]]],
   [[32767, True, False], [10, False, False], [0, False, False]]],
  ['control: wrap with cleared traps',
   [False,
    [[30000, 5000, 'ADD', True],
     [-30000, 5000, 'SUB', True],
     [200, 200, 'MUL', False],
     [1, 1, 'ADD', False]]],
   [[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']],
  ['control: exact limits',
   [False, [[-32767, 1, 'SUB', False], [32766, 1, 'ADD', False], [3, 4, 'MUL', False]]],
   [[-32768, False, False], [32767, False, False], [12, False, False]]],
  ['regression: scenario 1',
   [False,
    [[-32768, -20192, 'SUB', True],
     [12968, -30310, 'ADD', False],
     [-31305, 2, 'SUB', False],
     [11091, 200, 'MUL', True],
     [10310, 200, 'SUB', False]]],
   [[-12576, False, False],
    [-17342, False, False],
    [-31307, False, False],
    [-10024, True, False],
    [10110, False, False]]],
  ['control: scenario 2',
   [True,
    [[27834, -6307, 'SUB', False],
     [30000, -15473, 'SUB', False],
     [-1, 1, 'MUL', False],
     [-30000, -4507, 'SUB', True],
     [-21177, 21481, 'MUL', False],
     [31159, 1, 'SUB', False]]],
   [[32767, True, True], 'halted']],
  ['control: scenario 3',
   [False,
    [[18788, 200, 'SUB', True],
     [20369, -23104, 'MUL', False],
     [-32768, 10449, 'ADD', False],
     [-17550, 18799, 'ADD', False],
     [1, 32767, 'MUL', False]]],
   [[18588, False, False], [8640, True, True], 'halted']],
  ['control: scenario 4',
   [False,
    [[30000, 1, 'ADD', True],
     [-20338, 30000, 'ADD', True],
     [18879, 1, 'SUB', True],
     [27305, -32768, 'MUL', True],
     [16107, -9800, 'MUL', False],
     [3999, -32768, 'SUB', False],
     [1, -21623, 'ADD', False]]],
   [[30001, False, False],
    [9662, False, False],
    [18878, False, False],
    [-32768, True, False],
    [27624, True, True],
    'halted']]],
 [['regression: overflow then clean ops',
   [True, [[32767, 1, 'ADD', True], [5, 5, 'ADD', False], [7, 7, 'SUB', False]]],
   [[32767, True, False], [10, False, False], [0, False, False]]],
  ['regression: scenario 3',
   [False,
    [[-10436, -32034, 'MUL', True],
     [2, 22108, 'SUB', False],
     [7659, 2, 'MUL', False],
     [5339, 1, 'MUL', False]]],
   [[7688, True, False], [-22106, False, False], [15318, False, False], [5339, False, False]]],
  ['control: wrap with cleared traps',
   [False,
    [[30000, 5000, 'ADD', True],
     [-30000, 5000, 'SUB', True],
     [200, 200, 'MUL', False],
     [1, 1, 'ADD', False]]],
   [[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']],
  ['regression: saturation both signs',
   [True,
    [[-2, -20000, 'MUL', True],
     [-20000, 20000, 'SUB', True],
     [32767, 0, 'ADD', False],
     [1, 1, 'ADD', False]]],
   [[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]],
  ['control: exact limits',
   [False, [[-32767, 1, 'SUB', False], [32766, 1, 'ADD', False], [3, 4, 'MUL', False]]],
   [[-32768, False, False], [32767, False, False], [12, False, False]]],
  ['control: scenario 1',
   [False,
    [[-15041, -14459, 'SUB', False],
     [13071, -30000, 'ADD', True],
     [-17526, -1, 'MUL', True],
     [-30000, 200, 'MUL', False]]],
   [[-582, False, False], [-16929, False, False], [17526, False, False], [29312, True, True], 'halted']],
  ['control: scenario 2',
   [True,
    [[-1048, 30000, 'ADD', False],
     [2, -13120, 'SUB', False],
     [29306, -32768, 'SUB', True],
     [-9919, -24931, 'MUL', True]]],
   [[28952, False, False], [13122, False, False], [32767, True, False], [32767, True, False]]],
  ['regression: scenario 4',
   [False,
    [[200, -21485, 'MUL', True],
     [-200, -32768, 'SUB', True],
     [15677, 32607, 'ADD', True],
     [-10557, 26430, 'SUB', False],
     [-200, 30000, 'SUB', True],
     [-30000, 200, 'ADD', True],
     [26687, -20358, 'ADD', False]]],
   [[28376, True, False], [32568, False, False], [-17252, True, False], [28549, True, True], 'halted']]],
 [['regression: scenario 8',
   [False,
    [[-4887, -27663, 'SUB', True],
     [30000, 6920, 'MUL', True],
     [28114, 1, 'SUB', False],
     [1, -5974, 'SUB', False]]],
   [[22776, False, False], [-18048, True, False], [28113, False, False], [5975, False, False]]],
  ['regression: scenario 12',
   [True,
    [[-200, -14943, 'ADD', True],
     [2, 30000, 'SUB', True],
     [2, -32768, 'SUB', True],
     [24257, -25508, 'SUB', True],
     [932, -29592, 'SUB', False],
     [-32768, -15582, 'ADD', False],
     [25886, -200, 'SUB', False],
     [15203, -12133, 'SUB', False]]],
   [[-15143, False, False],
    [-29998, False, False],
    [32767, True, False],
    [32767, True, False],
    [30524, False, False],
    [-32768, True, True],
    'halted']],
  ['control: wrap with cleared traps',
   [False,
    [[30000, 5000, 'ADD', True],
     [-30000, 5000, 'SUB', True],
     [200, 200, 'MUL', False],
     [1, 1, 'ADD', False]]],
   [[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']],
  ['regression: saturation both signs',
   [True,
    [[-2, -20000, 'MUL', True],
     [-20000, 20000, 'SUB', True],
     [32767, 0, 'ADD', False],
     [1, 1, 'ADD', False]]],
   [[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]],
  ['control: exact limits',
   [False, [[-32767, 1, 'SUB', False], [32766, 1, 'ADD', False], [3, 4, 'MUL', False]]],
   [[-32768, False, False], [32767, False, False], [12, False, False]]],
  ['regression: overflow then clean ops',
   [True, [[32767, 1, 'ADD', True], [5, 5, 'ADD', False], [7, 7, 'SUB', False]]],
   [[32767, True, False], [10, False, False], [0, False, False]]],
  ['control: scenario 1',
   [False,
    [[15094, -24454, 'MUL', False],
     [-30000, 24363, 'MUL', True],
     [2, -14871, 'MUL', False],
     [1, -26550, 'MUL', True],
     [-1, -7090, 'SUB', False],
     [32767, 1, 'MUL', True],
     [-32768, 15967, 'ADD', False],
     [21457, -28729, 'SUB', True]]],
   [[-9924, True, True], 'halted']],
  ['control: scenario 2',
   [False,
    [[-200, -200, 'ADD', True],
     [32767, 200, 'MUL', False],
     [-9390, 1, 'MUL', False],
     [-11169, -28064, 'ADD', True],
     [22720, -1, 'ADD', False],
     [-200, -1, 'ADD', False],
     [-12859, 1, 'ADD', True]]],
   [[-400, False, False], [-200, True, True], 'halted']]],
 [['regression: scenario 3',
   [False,
    [[-32768, 19187, 'MUL', True],
     [-7301, -200, 'SUB', False],
     [-32768, 30000, 'SUB', True],
     [-9747, -24186, 'ADD', True],
     [-1, -22920, 'SUB', True],
     [-259, 22293, 'SUB', False],
     [23494, -1, 'MUL', False],
     [-32529, 24353, 'SUB', True]]],
   [[-32768, True, False],
    [-7101, False, False],
    [2768, True, False],
    [31603, True, False],
    [22919, False, False],
    [-22552, False, False],
    [-23494, False, False],
    [8654, True, False]]],
  ['regression: scenario 31',
   [True,
    [[-2900, -200, 'MUL', True],
     [23750, 200, 'SUB', False],
     [200, -31152, 'MUL', True],
     [30000, -32768, 'SUB', True]]],
   [[32767, True, False], [23550, False, False], [-32768, True, False], [32767, True, False]]],
  ['control: wrap with cleared traps',
   [False,
    [[30000, 5000, 'ADD', True],
     [-30000, 5000, 'SUB', True],
     [200, 200, 'MUL', False],
     [1, 1, 'ADD', False]]],
   [[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']],
  ['regression: saturation both signs',
   [True,
    [[-2, -20000, 'MUL', True],
     [-20000, 20000, 'SUB', True],
     [32767, 0, 'ADD', False],
     [1, 1, 'ADD', False]]],
   [[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]],
  ['control: exact limits',
   [False, [[-32767, 1, 'SUB', False], [32766, 1, 'ADD', False], [3, 4, 'MUL', False]]],
   [[-32768, False, False], [32767, False, False], [12, False, False]]],
  ['regression: overflow then clean ops',
   [True, [[32767, 1, 'ADD', True], [5, 5, 'ADD', False], [7, 7, 'SUB', False]]],
   [[32767, True, False], [10, False, False], [0, False, False]]],
  ['control: scenario 1',
   [False,
    [[-26759, 2, 'SUB', True],
     [-30000, -32768, 'SUB', False],
     [-3730, -31438, 'ADD', False],
     [200, 200, 'SUB', True],
     [-24761, 200, 'SUB', True],
     [-20747, 200, 'SUB', False],
     [200, 19789, 'SUB', True]]],
   [[-26761, False, False], [2768, False, False], [30368, True, True], 'halted']],
  ['regression: scenario 2',
   [False,
    [[30000, -32768, 'ADD', True],
     [4451, 31437, 'SUB', False],
     [-1, 22093, 'MUL', False],
     [-30000, -18488, 'SUB', False],
     [30000, -28921, 'MUL', True],
     [-200, 23349, 'ADD', True],
     [-32768, 200, 'SUB', False]]],
   [[-2768, False, False],
    [-26986, False, False],
    [-22093, False, False],
    [-11512, False, False],
    [1104, True, False],
    [23149, False, False],
    [32568, True, True],
    'halted']]],
 [['regression: scenario 13',
   [False,
    [[-30088, 16833, 'SUB', True],
     [1555, 200, 'ADD', False],
     [200, -31213, 'SUB', True],
     [-10659, -15907, 'MUL', False],
     [2, -10563, 'ADD', True],
     [-9064, 16082, 'ADD', True],
     [30646, -1, 'ADD', True],
     [10428, 200, 'ADD', True]]],
   [[18615, True, False], [1755, False, False], [31413, False, False], [11081, True, True], 'halted']],
  ['regression: scenario 18',
   [True,
    [[-24623, 2, 'MUL', True],
     [-200, -32768, 'MUL', True],
     [1, -1, 'SUB', False],
     [-22404, -5569, 'SUB', True],
     [30526, 30000, 'MUL', True]]],
   [[-32768, True, False],
    [32767, True, False],
    [2, False, False],
    [-16835, False, False],
    [32767, True, False]]],
  ['control: wrap with cleared traps',
   [False,
    [[30000, 5000, 'ADD', True],
     [-30000, 5000, 'SUB', True],
     [200, 200, 'MUL', False],
     [1, 1, 'ADD', False]]],
   [[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']],
  ['regression: saturation both signs',
   [True,
    [[-2, -20000, 'MUL', True],
     [-20000, 20000, 'SUB', True],
     [32767, 0, 'ADD', False],
     [1, 1, 'ADD', False]]],
   [[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]],
  ['control: exact limits',
   [False, [[-32767, 1, 'SUB', False], [32766, 1, 'ADD', False], [3, 4, 'MUL', False]]],
   [[-32768, False, False], [32767, False, False], [12, False, False]]],
  ['regression: overflow then clean ops',
   [True, [[32767, 1, 'ADD', True], [5, 5, 'ADD', False], [7, 7, 'SUB', False]]],
   [[32767, True, False], [10, False, False], [0, False, False]]],
  ['control: scenario 1',
   [True,
    [[160, 2, 'SUB', True], [200, 200, 'SUB', True], [222, 200, 'SUB', False], [200, -32768, 'ADD', True]]],
   [[158, False, False], [0, False, False], [22, False, False], [-32568, False, False]]],
  ['control: scenario 2',
   [True,
    [[30000, 1574, 'SUB', True],
     [-783, -29319, 'SUB', True],
     [2, 1803, 'SUB', False],
     [200, 2, 'ADD', True],
     [9942, 32767, 'MUL', True],
     [-30000, -19084, 'MUL', True],
     [-10106, -30460, 'ADD', False],
     [2, 32767, 'ADD', True]]],
   [[28426, False, False],
    [28536, False, False],
    [-1801, False, False],
    [202, False, False],
    [32767, True, False],
    [32767, True, False],
    [-32768, True, True],
    'halted']]]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
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 fixture	Actual	Expected	Outcome
regression: saturation both signs	`[[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]`	`[[32767, True, False], [-32768, True, False], [32767, False, False], [2, False, False]]`	Passed
regression: overflow then clean ops	`[[32767, True, False], [10, False, False], [0, False, False]]`	`[[32767, True, False], [10, False, False], [0, False, False]]`	Passed
control: wrap with cleared traps	`[[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']`	`[[-30536, True, False], [30536, True, False], [-25536, True, True], 'halted']`	Passed
control: exact limits	`[[-32768, False, False], [32767, False, False], [12, False, False]]`	`[[-32768, False, False], [32767, False, False], [12, False, False]]`	Passed
regression: scenario 1	`[[-12576, False, False], [-17342, False, False], [-31307, False, False], [-10024, True, False], [10110, False, False]]`	`[[-12576, False, False], [-17342, False, False], [-31307, False, False], [-10024, True, False], [10110, False, False]]`	Passed
control: scenario 2	`[[32767, True, True], 'halted']`	`[[32767, True, True], 'halted']`	Passed
control: scenario 3	`[[18588, False, False], [8640, True, True], 'halted']`	`[[18588, False, False], [8640, True, True], 'halted']`	Passed
control: scenario 4	`[[30001, False, False], [9662, False, False], [18878, False, False], [-32768, True, False], [27624, True, True], 'halted']`	`[[30001, False, False], [9662, False, False], [18878, False, False], [-32768, True, False], [27624, True, True], 'halted']`	Passed

SHA-256 / ca1734efdbf7e32409ede41722dfad246fa45f3d003c90ba850754d95aacde04

Verification & scope

A deterministic bounded teaching model of one PLC instruction or rung pattern evaluated scan by scan. The stated contract is a stipulated toy convention, not a claim of conformance to any vendor controller or IEC 61131-3 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.

Observations recorded using Python 3.12.14 at 2026-09-29T14:51:44.688471+00:00.

Case digest / 088ea77645c018dd2010df47d8e9c719589a5e6ba35b2b19f44c9c039bc92d52