FA-90056 / Bytecode virtual machines / Open access

Method descriptors: void arrays accepted as return type · case 01

A descriptor returning [V loads as returning an array of void.

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

ROOT CAUSE

The V branch checks the return-position flag but not the array dimension count.

THE FAILURE

The V branch checks the return-position flag but not the array dimension count.

Unsuccessful approach: Dropping the return-position flag accepts V as a parameter type.

Case contract

Parse a method descriptor "(args)ret". Field types: B C D F I J S Z, L<binary name>; with a non-empty name, and up to 255 leading "[" dimensions. V is allowed only as a non-array return type. Local-slot count: one extra slot for "this" unless static; J and D take two slots unless they are array element types. Return {args (readable names, "[]" per dimension), slots, ret} or ["ClassFormatError", position].

Why this case matters

Frame sizes and argument placement in bytecode VMs are derived from descriptors.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(desc, is_static):
    names = {'B': 'byte', 'C': 'char', 'D': 'double', 'F': 'float', 'I': 'int', 'J': 'long', 'S': 'short', 'Z': 'boolean'}
    def field(i, allow_void):
        dims = 0
        while i < len(desc) and desc[i] == '[':
            dims += 1
            i += 1
        if dims > 255 or i >= len(desc):
            return None, i, 0
        c = desc[i]
        if c == 'L':
            j = desc.find(';', i)
            if j < 0 or j == i + 1:
                return None, i, 0
            base = desc[i + 1:j].replace('/', '.')
            i = j + 1
        elif c in names:
            base = names[c]
            i += 1
        elif c == 'V' and allow_void:
            base = 'void'
            i += 1
        else:
            return None, i, 0
        width = 2 if dims == 0 and c in 'JD' else 1
        return base + '[]' * dims, i, width
    if not desc.startswith('('):
        return ['ClassFormatError', 0]
    i = 1
    args = []
    slots = 0 if is_static else 1
    while i < len(desc) and desc[i] != ')':
        t, i, w = field(i, False)
        if t is None:
            return ['ClassFormatError', i]
        args.append(t)
        slots += w
    if i >= len(desc):
        return ['ClassFormatError', i]
    ret, j, _ = field(i + 1, True)
    if ret is None or j != len(desc):
        return ['ClassFormatError', j]
    return {'args': args, 'slots': slots, 'ret': ret}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('regression: mixed wide and array arguments',
   ('(IJ[JD[[Ljava/lang/String;I)V', True),
   {'args': ['int', 'long', 'long[]', 'double', 'java.lang.String[][]', 'int'], 'ret': 'void', 'slots': 8}),
  ('instance method reserves this slot',
   ('(JDI)J', False),
   {'args': ['long', 'double', 'int'], 'ret': 'long', 'slots': 6}),
  ('void array return rejected', ('(I)[V', True), ['ClassFormatError', 4]),
  ('void argument rejected', ('(IV)V', True), ['ClassFormatError', 2]),
  ('empty class name rejected', ('(IL;)V', False), ['ClassFormatError', 2]),
  ('trailing characters rejected', ('(ILpkg/A;)Lpkg/B;x', False), ['ClassFormatError', 17]),
  ('255 array dimensions accepted',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[II)V',
    True),
   {'args': ['int[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]',
             'int'],
    'ret': 'void',
    'slots': 2}),
  ('256 array dimensions rejected',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[II)V',
    True),
   ['ClassFormatError', 257]),
  ('control: missing parenthesis', ('I)V', True), ['ClassFormatError', 0])],
 [('regression: mixed wide and array arguments',
   ('(IJ[JD[[Ljava/lang/String;II)V', True),
   {'args': ['int', 'long', 'long[]', 'double', 'java.lang.String[][]', 'int', 'int'],
    'ret': 'void',
    'slots': 9}),
  ('instance method reserves this slot',
   ('(JDII)J', False),
   {'args': ['long', 'double', 'int', 'int'], 'ret': 'long', 'slots': 7}),
  ('void array return rejected', ('(II)[V', True), ['ClassFormatError', 5]),
  ('void argument rejected', ('(IIV)V', True), ['ClassFormatError', 3]),
  ('empty class name rejected', ('(IIL;)V', False), ['ClassFormatError', 3]),
  ('trailing characters rejected', ('(IILpkg/A;)Lpkg/B;x', False), ['ClassFormatError', 18]),
  ('255 array dimensions accepted',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[III)V',
    True),
   {'args': ['int[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]',
             'int',
             'int'],
    'ret': 'void',
    'slots': 3}),
  ('256 array dimensions rejected',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[III)V',
    True),
   ['ClassFormatError', 257]),
  ('control: missing parenthesis', ('I)V', True), ['ClassFormatError', 0])],
 [('regression: mixed wide and array arguments',
   ('(IJ[JD[[Ljava/lang/String;III)V', True),
   {'args': ['int', 'long', 'long[]', 'double', 'java.lang.String[][]', 'int', 'int', 'int'],
    'ret': 'void',
    'slots': 10}),
  ('instance method reserves this slot',
   ('(JDIII)J', False),
   {'args': ['long', 'double', 'int', 'int', 'int'], 'ret': 'long', 'slots': 8}),
  ('void array return rejected', ('(III)[V', True), ['ClassFormatError', 6]),
  ('void argument rejected', ('(IIIV)V', True), ['ClassFormatError', 4]),
  ('empty class name rejected', ('(IIIL;)V', False), ['ClassFormatError', 4]),
  ('trailing characters rejected', ('(IIILpkg/A;)Lpkg/B;x', False), ['ClassFormatError', 19]),
  ('255 array dimensions accepted',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[IIII)V',
    True),
   {'args': ['int[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]',
             'int',
             'int',
             'int'],
    'ret': 'void',
    'slots': 4}),
  ('256 array dimensions rejected',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[IIII)V',
    True),
   ['ClassFormatError', 257]),
  ('control: missing parenthesis', ('I)V', True), ['ClassFormatError', 0])],
 [('regression: mixed wide and array arguments',
   ('(IJ[JD[[Ljava/lang/String;IIII)V', True),
   {'args': ['int', 'long', 'long[]', 'double', 'java.lang.String[][]', 'int', 'int', 'int', 'int'],
    'ret': 'void',
    'slots': 11}),
  ('instance method reserves this slot',
   ('(JDIIII)J', False),
   {'args': ['long', 'double', 'int', 'int', 'int', 'int'], 'ret': 'long', 'slots': 9}),
  ('void array return rejected', ('(IIII)[V', True), ['ClassFormatError', 7]),
  ('void argument rejected', ('(IIIIV)V', True), ['ClassFormatError', 5]),
  ('empty class name rejected', ('(IIIIL;)V', False), ['ClassFormatError', 5]),
  ('trailing characters rejected', ('(IIIILpkg/A;)Lpkg/B;x', False), ['ClassFormatError', 20]),
  ('255 array dimensions accepted',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[IIIII)V',
    True),
   {'args': ['int[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]',
             'int',
             'int',
             'int',
             'int'],
    'ret': 'void',
    'slots': 5}),
  ('256 array dimensions rejected',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[IIIII)V',
    True),
   ['ClassFormatError', 257]),
  ('control: missing parenthesis', ('I)V', True), ['ClassFormatError', 0])],
 [('regression: mixed wide and array arguments',
   ('(IJ[JD[[Ljava/lang/String;IIIII)V', True),
   {'args': ['int', 'long', 'long[]', 'double', 'java.lang.String[][]', 'int', 'int', 'int', 'int', 'int'],
    'ret': 'void',
    'slots': 12}),
  ('instance method reserves this slot',
   ('(JDIIIII)J', False),
   {'args': ['long', 'double', 'int', 'int', 'int', 'int', 'int'], 'ret': 'long', 'slots': 10}),
  ('void array return rejected', ('(IIIII)[V', True), ['ClassFormatError', 8]),
  ('void argument rejected', ('(IIIIIV)V', True), ['ClassFormatError', 6]),
  ('empty class name rejected', ('(IIIIIL;)V', False), ['ClassFormatError', 6]),
  ('trailing characters rejected', ('(IIIIILpkg/A;)Lpkg/B;x', False), ['ClassFormatError', 21]),
  ('255 array dimensions accepted',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[IIIIII)V',
    True),
   {'args': ['int[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]',
             'int',
             'int',
             'int',
             'int',
             'int'],
    'ret': 'void',
    'slots': 6}),
  ('256 array dimensions rejected',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[IIIIII)V',
    True),
   ['ClassFormatError', 257]),
  ('control: missing parenthesis', ('I)V', True), ['ClassFormatError', 0])]]
for label, args, expected in cases[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: mixed wide and array arguments	`{'args': ['int', 'long', 'long[]', 'double', 'java.lang.String[][]', 'int'], 'ret': 'void', 'slots': 8}`	`{'args': ['int', 'long', 'long[]', 'double', 'java.lang.String[][]', 'int'], 'ret': 'void', 'slots': 8}`	Passed
instance method reserves this slot	`{'args': ['long', 'double', 'int'], 'ret': 'long', 'slots': 6}`	`{'args': ['long', 'double', 'int'], 'ret': 'long', 'slots': 6}`	Passed
void array return rejected	`{'args': ['int'], 'ret': 'void[]', 'slots': 1}`	`['ClassFormatError', 4]`	Failed
void argument rejected	`['ClassFormatError', 2]`	`['ClassFormatError', 2]`	Passed
empty class name rejected	`['ClassFormatError', 2]`	`['ClassFormatError', 2]`	Passed
trailing characters rejected	`['ClassFormatError', 17]`	`['ClassFormatError', 17]`	Passed
255 array dimensions accepted	{'args': ['int[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]', 'int'], 'ret': 'void', 'slots': 2}	{'args': ['int[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]', 'int'], 'ret': 'void', 'slots': 2}	Passed
256 array dimensions rejected	`['ClassFormatError', 257]`	`['ClassFormatError', 257]`	Passed
control: missing parenthesis	`['ClassFormatError', 0]`	`['ClassFormatError', 0]`	Passed

SHA-256 / 263221d89cd22aa7c7749eb1df56b0c9285900790338a7a0ff6d768303eec806

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(desc, is_static):
    names = {'B': 'byte', 'C': 'char', 'D': 'double', 'F': 'float', 'I': 'int', 'J': 'long', 'S': 'short', 'Z': 'boolean'}
    def field(i, allow_void):
        dims = 0
        while i < len(desc) and desc[i] == '[':
            dims += 1
            i += 1
        if dims > 255 or i >= len(desc):
            return None, i, 0
        c = desc[i]
        if c == 'L':
            j = desc.find(';', i)
            if j < 0 or j == i + 1:
                return None, i, 0
            base = desc[i + 1:j].replace('/', '.')
            i = j + 1
        elif c in names:
            base = names[c]
            i += 1
        elif c == 'V' and dims == 0:
            base = 'void'
            i += 1
        else:
            return None, i, 0
        width = 2 if dims == 0 and c in 'JD' else 1
        return base + '[]' * dims, i, width
    if not desc.startswith('('):
        return ['ClassFormatError', 0]
    i = 1
    args = []
    slots = 0 if is_static else 1
    while i < len(desc) and desc[i] != ')':
        t, i, w = field(i, False)
        if t is None:
            return ['ClassFormatError', i]
        args.append(t)
        slots += w
    if i >= len(desc):
        return ['ClassFormatError', i]
    ret, j, _ = field(i + 1, True)
    if ret is None or j != len(desc):
        return ['ClassFormatError', j]
    return {'args': args, 'slots': slots, 'ret': ret}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('regression: mixed wide and array arguments',
   ('(IJ[JD[[Ljava/lang/String;I)V', True),
   {'args': ['int', 'long', 'long[]', 'double', 'java.lang.String[][]', 'int'], 'ret': 'void', 'slots': 8}),
  ('instance method reserves this slot',
   ('(JDI)J', False),
   {'args': ['long', 'double', 'int'], 'ret': 'long', 'slots': 6}),
  ('void array return rejected', ('(I)[V', True), ['ClassFormatError', 4]),
  ('void argument rejected', ('(IV)V', True), ['ClassFormatError', 2]),
  ('empty class name rejected', ('(IL;)V', False), ['ClassFormatError', 2]),
  ('trailing characters rejected', ('(ILpkg/A;)Lpkg/B;x', False), ['ClassFormatError', 17]),
  ('255 array dimensions accepted',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[II)V',
    True),
   {'args': ['int[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]',
             'int'],
    'ret': 'void',
    'slots': 2}),
  ('256 array dimensions rejected',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[II)V',
    True),
   ['ClassFormatError', 257]),
  ('control: missing parenthesis', ('I)V', True), ['ClassFormatError', 0])],
 [('regression: mixed wide and array arguments',
   ('(IJ[JD[[Ljava/lang/String;II)V', True),
   {'args': ['int', 'long', 'long[]', 'double', 'java.lang.String[][]', 'int', 'int'],
    'ret': 'void',
    'slots': 9}),
  ('instance method reserves this slot',
   ('(JDII)J', False),
   {'args': ['long', 'double', 'int', 'int'], 'ret': 'long', 'slots': 7}),
  ('void array return rejected', ('(II)[V', True), ['ClassFormatError', 5]),
  ('void argument rejected', ('(IIV)V', True), ['ClassFormatError', 3]),
  ('empty class name rejected', ('(IIL;)V', False), ['ClassFormatError', 3]),
  ('trailing characters rejected', ('(IILpkg/A;)Lpkg/B;x', False), ['ClassFormatError', 18]),
  ('255 array dimensions accepted',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[III)V',
    True),
   {'args': ['int[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]',
             'int',
             'int'],
    'ret': 'void',
    'slots': 3}),
  ('256 array dimensions rejected',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[III)V',
    True),
   ['ClassFormatError', 257]),
  ('control: missing parenthesis', ('I)V', True), ['ClassFormatError', 0])],
 [('regression: mixed wide and array arguments',
   ('(IJ[JD[[Ljava/lang/String;III)V', True),
   {'args': ['int', 'long', 'long[]', 'double', 'java.lang.String[][]', 'int', 'int', 'int'],
    'ret': 'void',
    'slots': 10}),
  ('instance method reserves this slot',
   ('(JDIII)J', False),
   {'args': ['long', 'double', 'int', 'int', 'int'], 'ret': 'long', 'slots': 8}),
  ('void array return rejected', ('(III)[V', True), ['ClassFormatError', 6]),
  ('void argument rejected', ('(IIIV)V', True), ['ClassFormatError', 4]),
  ('empty class name rejected', ('(IIIL;)V', False), ['ClassFormatError', 4]),
  ('trailing characters rejected', ('(IIILpkg/A;)Lpkg/B;x', False), ['ClassFormatError', 19]),
  ('255 array dimensions accepted',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[IIII)V',
    True),
   {'args': ['int[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]',
             'int',
             'int',
             'int'],
    'ret': 'void',
    'slots': 4}),
  ('256 array dimensions rejected',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[IIII)V',
    True),
   ['ClassFormatError', 257]),
  ('control: missing parenthesis', ('I)V', True), ['ClassFormatError', 0])],
 [('regression: mixed wide and array arguments',
   ('(IJ[JD[[Ljava/lang/String;IIII)V', True),
   {'args': ['int', 'long', 'long[]', 'double', 'java.lang.String[][]', 'int', 'int', 'int', 'int'],
    'ret': 'void',
    'slots': 11}),
  ('instance method reserves this slot',
   ('(JDIIII)J', False),
   {'args': ['long', 'double', 'int', 'int', 'int', 'int'], 'ret': 'long', 'slots': 9}),
  ('void array return rejected', ('(IIII)[V', True), ['ClassFormatError', 7]),
  ('void argument rejected', ('(IIIIV)V', True), ['ClassFormatError', 5]),
  ('empty class name rejected', ('(IIIIL;)V', False), ['ClassFormatError', 5]),
  ('trailing characters rejected', ('(IIIILpkg/A;)Lpkg/B;x', False), ['ClassFormatError', 20]),
  ('255 array dimensions accepted',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[IIIII)V',
    True),
   {'args': ['int[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]',
             'int',
             'int',
             'int',
             'int'],
    'ret': 'void',
    'slots': 5}),
  ('256 array dimensions rejected',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[IIIII)V',
    True),
   ['ClassFormatError', 257]),
  ('control: missing parenthesis', ('I)V', True), ['ClassFormatError', 0])],
 [('regression: mixed wide and array arguments',
   ('(IJ[JD[[Ljava/lang/String;IIIII)V', True),
   {'args': ['int', 'long', 'long[]', 'double', 'java.lang.String[][]', 'int', 'int', 'int', 'int', 'int'],
    'ret': 'void',
    'slots': 12}),
  ('instance method reserves this slot',
   ('(JDIIIII)J', False),
   {'args': ['long', 'double', 'int', 'int', 'int', 'int', 'int'], 'ret': 'long', 'slots': 10}),
  ('void array return rejected', ('(IIIII)[V', True), ['ClassFormatError', 8]),
  ('void argument rejected', ('(IIIIIV)V', True), ['ClassFormatError', 6]),
  ('empty class name rejected', ('(IIIIIL;)V', False), ['ClassFormatError', 6]),
  ('trailing characters rejected', ('(IIIIILpkg/A;)Lpkg/B;x', False), ['ClassFormatError', 21]),
  ('255 array dimensions accepted',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[IIIIII)V',
    True),
   {'args': ['int[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]',
             'int',
             'int',
             'int',
             'int',
             'int'],
    'ret': 'void',
    'slots': 6}),
  ('256 array dimensions rejected',
   ('([[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[IIIIII)V',
    True),
   ['ClassFormatError', 257]),
  ('control: missing parenthesis', ('I)V', True), ['ClassFormatError', 0])]]
for label, args, expected in cases[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: mixed wide and array arguments	`{'args': ['int', 'long', 'long[]', 'double', 'java.lang.String[][]', 'int'], 'ret': 'void', 'slots': 8}`	`{'args': ['int', 'long', 'long[]', 'double', 'java.lang.String[][]', 'int'], 'ret': 'void', 'slots': 8}`	Passed
instance method reserves this slot	`{'args': ['long', 'double', 'int'], 'ret': 'long', 'slots': 6}`	`{'args': ['long', 'double', 'int'], 'ret': 'long', 'slots': 6}`	Passed
void array return rejected	`['ClassFormatError', 4]`	`['ClassFormatError', 4]`	Passed
void argument rejected	`{'args': ['int', 'void'], 'ret': 'void', 'slots': 2}`	`['ClassFormatError', 2]`	Failed
empty class name rejected	`['ClassFormatError', 2]`	`['ClassFormatError', 2]`	Passed
trailing characters rejected	`['ClassFormatError', 17]`	`['ClassFormatError', 17]`	Passed
255 array dimensions accepted	{'args': ['int[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]', 'int'], 'ret': 'void', 'slots': 2}	{'args': ['int[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]', 'int'], 'ret': 'void', 'slots': 2}	Passed
256 array dimensions rejected	`['ClassFormatError', 257]`	`['ClassFormatError', 257]`	Passed
control: missing parenthesis	`['ClassFormatError', 0]`	`['ClassFormatError', 0]`	Passed

SHA-256 / 3a1964294842f7e0c33468bc4efe936cffa1c57cb3fbe8ea7ca09079741fc0dc

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.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

Verification & scope

A deterministic, bounded teaching model of one bytecode virtual machine mechanism with a stipulated instruction encoding; it is not a production VM and claims no conformance to any real specification. 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 2026-09-29T14:51:23.262830+00:00.

Case digest / 522b6d81e686aaf2ee21a12b3ea27dc38a0b7fb98136ef9b719ba3a39cf6f2dc