FA-79466 / Barcode symbology encoding / Open access

Standard Code 39 silently upper-cases lowercase input · case 01

Case-sensitive part numbers scan back in capitals without any error.

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

ROOT CAUSE

Lowercase is upper-cased before validation instead of being rejected in standard mode.

VERIFIED REPAIR

Reject characters outside the 43-character set; lowercase requires full ASCII mode.

Unsuccessful approach: Validating the upper-cased text but emitting the original puts unencodable lowercase into the symbol.

Case contract

Encode text for Code 39 with a wide:narrow ratio of 2 or 3. Standard mode accepts only the 43 characters 0-9 A-Z - . space $ / + %. Full ASCII mode maps lowercase to "+" plus the capital, controls 1..26 to "$" plus A..Z, NUL to %U, 27..31 to %A..%E, DEL to %T, and punctuation (including the four standard shift characters $ % + /) to its two-character escape. Every symbol character, including the start/stop "*", has 6 narrow and 3 wide elements, and one narrow gap separates adjacent characters. Return the framed data and the total width in narrow modules.

Why this case matters

Retail, logistics, pharmacy and document workflows depend on encoders that produce exactly the module pattern, code-set switches, separators and quiet zones scanners expect; one misplaced module or separator makes a label unreadable or, worse, scan as different data.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(text, mode, ratio):
    std = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. $/+%'
    if ratio not in (2, 3):
        return {'error': 'ratio'}
    if mode == 'standard':
        enc = text.upper()
        for ch in enc:
            if ch not in std:
                return {'error': 'char', 'char': ch}
    else:
        punct = {'$': '/D', '%': '/E', '+': '/K', '/': '/O', '!': '/A', '"': '/B', '#': '/C', '&': '/F', "'": '/G',
                 '(': '/H', ')': '/I', '*': '/J', ',': '/L', ':': '/Z', ';': '%F', '<': '%G', '=': '%H', '>': '%I',
                 '?': '%J', '@': '%V', '[': '%K', '\\': '%L', ']': '%M', '^': '%N', '_': '%O', '`': '%W',
                 '{': '%P', '|': '%Q', '}': '%R', '~': '%S'}
        enc = ''
        for ch in text:
            o = ord(ch)
            if o > 127:
                return {'error': 'char', 'char': ch}
            if ch in punct:
                enc += punct[ch]
            elif 'a' <= ch <= 'z':
                enc += '+' + ch.upper()
            elif 1 <= o <= 26:
                enc += '$' + chr(o + 64)
            elif o == 0:
                enc += '%U'
            elif 27 <= o <= 31:
                enc += '%' + chr(o - 27 + 65)
            elif o == 127:
                enc += '%T'
            else:
                enc += ch
    count = len(enc) + 2
    return {'data': '*' + enc + '*', 'modules': count * (6 + 3 * ratio) + (count - 1)}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[('Z-9a+blot', 'standard', 2), {'error': 'char', 'char': 'a'}], [('café', 'standard', 2), {'error': 'char', 'char': 'c'}], [('café', 'standard', 4), {'error': 'ratio'}], [('ABPN/7PN/7', 'full', 1), {'error': 'ratio'}], [('a+ba+b', 'full', 4), {'error': 'ratio'}], [('café\t', 'full', 4), {'error': 'ratio'}], [('Z-9', 'standard', 4), {'error': 'ratio'}], [('café', 'standard', 3), {'error': 'char', 'char': 'c'}]], [[('lotZ-9', 'standard', 2), {'error': 'char', 'char': 'l'}], [('$5lot', 'standard', 2), {'error': 'char', 'char': 'l'}], [('', 'standard', 1), {'error': 'ratio'}], [('\x1blotlot', 'full', 2), {'data': '*%A+L+O+T+L+O+T*', 'modules': 207}], [('#1', 'full', 2), {'data': '*/C1*', 'modules': 64}], [('ABa+b', 'full', 2), {'data': '*AB+A/K+B*', 'modules': 129}], [('', 'full', 3), {'data': '**', 'modules': 31}], [('café', 'standard', 2), {'error': 'char', 'char': 'c'}]], [[('lot', 'standard', 3), {'error': 'char', 'char': 'l'}], [('12q*', 'standard', 3), {'error': 'char', 'char': 'q'}], [('a+bAB', 'full', 2), {'data': '*+A/K+BAB*', 'modules': 129}], [('#1café', 'standard', 4), {'error': 'ratio'}], [('ABPN/7Z-9', 'full', 2), {'data': '*ABPN/O7Z-9*', 'modules': 155}], [(' ', 'full', 1), {'error': 'ratio'}], [('$5 \x00', 'full', 2), {'data': '*/D5 %U*', 'modules': 103}], [('a+b', 'standard', 3), {'error': 'char', 'char': 'a'}]], [[('a+b\t', 'standard', 3), {'error': 'char', 'char': 'a'}], [('Z-9x$5', 'standard', 2), {'error': 'char', 'char': 'x'}], [('qPN/7café', 'full', 2), {'error': 'char', 'char': 'é'}], [('AB\x00 ', 'full', 1), {'error': 'ratio'}], [('*', 'full', 2), {'data': '*/J*', 'modules': 51}], [('AB12', 'standard', 2), {'data': '*AB12*', 'modules': 77}], [('\x7f\tlot', 'full', 3), {'data': '*%T$I+L+O+T*', 'modules': 191}], [('x12', 'standard', 2), {'error': 'char', 'char': 'x'}]], [[('a+bcafécafé', 'standard', 2), {'error': 'char', 'char': 'a'}], [('x', 'standard', 2), {'error': 'char', 'char': 'x'}], [('$5lot', 'full', 3), {'data': '*/D5+L+O+T*', 'modules': 175}], [('\x00', 'full', 1), {'error': 'ratio'}], [('', 'standard', 2), {'data': '**', 'modules': 25}], [('', 'standard', 1), {'error': 'ratio'}], [('\x7f\x00', 'full', 4), {'error': 'ratio'}], [('1250%lot', 'standard', 2), {'error': 'char', 'char': 'l'}]]]
labels = ["regression: standard mode lowercase", "repair trap", "combined fault", "control", "control", "boundary", "boundary", "control"]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (labels[i % len(labels)], i), 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: standard mode lowercase 0	`{'data': 'Z-9A+BLOT', 'modules': 142}`	`{'char': 'a', 'error': 'char'}`	Failed
repair trap 1	`{'char': 'É', 'error': 'char'}`	`{'char': 'c', 'error': 'char'}`	Failed
combined fault 2	`{'error': 'ratio'}`	`{'error': 'ratio'}`	Passed
control 3	`{'error': 'ratio'}`	`{'error': 'ratio'}`	Passed
control 4	`{'error': 'ratio'}`	`{'error': 'ratio'}`	Passed
boundary 5	`{'error': 'ratio'}`	`{'error': 'ratio'}`	Passed
boundary 6	`{'error': 'ratio'}`	`{'error': 'ratio'}`	Passed
control 7	`{'char': 'É', 'error': 'char'}`	`{'char': 'c', 'error': 'char'}`	Failed

SHA-256 / a96700d7f773b35a10c6eb6b4be4072345ac3dd8f1cec1f0657ab64b72384b07

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(text, mode, ratio):
    std = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. $/+%'
    if ratio not in (2, 3):
        return {'error': 'ratio'}
    if mode == 'standard':
        for ch in text.upper():
            if ch not in std:
                return {'error': 'char', 'char': ch}
        enc = text
    else:
        punct = {'$': '/D', '%': '/E', '+': '/K', '/': '/O', '!': '/A', '"': '/B', '#': '/C', '&': '/F', "'": '/G',
                 '(': '/H', ')': '/I', '*': '/J', ',': '/L', ':': '/Z', ';': '%F', '<': '%G', '=': '%H', '>': '%I',
                 '?': '%J', '@': '%V', '[': '%K', '\\': '%L', ']': '%M', '^': '%N', '_': '%O', '`': '%W',
                 '{': '%P', '|': '%Q', '}': '%R', '~': '%S'}
        enc = ''
        for ch in text:
            o = ord(ch)
            if o > 127:
                return {'error': 'char', 'char': ch}
            if ch in punct:
                enc += punct[ch]
            elif 'a' <= ch <= 'z':
                enc += '+' + ch.upper()
            elif 1 <= o <= 26:
                enc += '$' + chr(o + 64)
            elif o == 0:
                enc += '%U'
            elif 27 <= o <= 31:
                enc += '%' + chr(o - 27 + 65)
            elif o == 127:
                enc += '%T'
            else:
                enc += ch
    count = len(enc) + 2
    return {'data': '*' + enc + '*', 'modules': count * (6 + 3 * ratio) + (count - 1)}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[('Z-9a+blot', 'standard', 2), {'error': 'char', 'char': 'a'}], [('café', 'standard', 2), {'error': 'char', 'char': 'c'}], [('café', 'standard', 4), {'error': 'ratio'}], [('ABPN/7PN/7', 'full', 1), {'error': 'ratio'}], [('a+ba+b', 'full', 4), {'error': 'ratio'}], [('café\t', 'full', 4), {'error': 'ratio'}], [('Z-9', 'standard', 4), {'error': 'ratio'}], [('café', 'standard', 3), {'error': 'char', 'char': 'c'}]], [[('lotZ-9', 'standard', 2), {'error': 'char', 'char': 'l'}], [('$5lot', 'standard', 2), {'error': 'char', 'char': 'l'}], [('', 'standard', 1), {'error': 'ratio'}], [('\x1blotlot', 'full', 2), {'data': '*%A+L+O+T+L+O+T*', 'modules': 207}], [('#1', 'full', 2), {'data': '*/C1*', 'modules': 64}], [('ABa+b', 'full', 2), {'data': '*AB+A/K+B*', 'modules': 129}], [('', 'full', 3), {'data': '**', 'modules': 31}], [('café', 'standard', 2), {'error': 'char', 'char': 'c'}]], [[('lot', 'standard', 3), {'error': 'char', 'char': 'l'}], [('12q*', 'standard', 3), {'error': 'char', 'char': 'q'}], [('a+bAB', 'full', 2), {'data': '*+A/K+BAB*', 'modules': 129}], [('#1café', 'standard', 4), {'error': 'ratio'}], [('ABPN/7Z-9', 'full', 2), {'data': '*ABPN/O7Z-9*', 'modules': 155}], [(' ', 'full', 1), {'error': 'ratio'}], [('$5 \x00', 'full', 2), {'data': '*/D5 %U*', 'modules': 103}], [('a+b', 'standard', 3), {'error': 'char', 'char': 'a'}]], [[('a+b\t', 'standard', 3), {'error': 'char', 'char': 'a'}], [('Z-9x$5', 'standard', 2), {'error': 'char', 'char': 'x'}], [('qPN/7café', 'full', 2), {'error': 'char', 'char': 'é'}], [('AB\x00 ', 'full', 1), {'error': 'ratio'}], [('*', 'full', 2), {'data': '*/J*', 'modules': 51}], [('AB12', 'standard', 2), {'data': '*AB12*', 'modules': 77}], [('\x7f\tlot', 'full', 3), {'data': '*%T$I+L+O+T*', 'modules': 191}], [('x12', 'standard', 2), {'error': 'char', 'char': 'x'}]], [[('a+bcafécafé', 'standard', 2), {'error': 'char', 'char': 'a'}], [('x', 'standard', 2), {'error': 'char', 'char': 'x'}], [('$5lot', 'full', 3), {'data': '*/D5+L+O+T*', 'modules': 175}], [('\x00', 'full', 1), {'error': 'ratio'}], [('', 'standard', 2), {'data': '**', 'modules': 25}], [('', 'standard', 1), {'error': 'ratio'}], [('\x7f\x00', 'full', 4), {'error': 'ratio'}], [('1250%lot', 'standard', 2), {'error': 'char', 'char': 'l'}]]]
labels = ["regression: standard mode lowercase", "repair trap", "combined fault", "control", "control", "boundary", "boundary", "control"]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (labels[i % len(labels)], i), 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: standard mode lowercase 0	`{'data': 'Z-9a+blot', 'modules': 142}`	`{'char': 'a', 'error': 'char'}`	Failed
repair trap 1	`{'char': 'É', 'error': 'char'}`	`{'char': 'c', 'error': 'char'}`	Failed
combined fault 2	`{'error': 'ratio'}`	`{'error': 'ratio'}`	Passed
control 3	`{'error': 'ratio'}`	`{'error': 'ratio'}`	Passed
control 4	`{'error': 'ratio'}`	`{'error': 'ratio'}`	Passed
boundary 5	`{'error': 'ratio'}`	`{'error': 'ratio'}`	Passed
boundary 6	`{'error': 'ratio'}`	`{'error': 'ratio'}`	Passed
control 7	`{'char': 'É', 'error': 'char'}`	`{'char': 'c', 'error': 'char'}`	Failed

SHA-256 / 4f8d0c109cc7a006f6e62d154a35a9e35a824ae139d6fdecba49c472710ccef1

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(text, mode, ratio):
    std = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. $/+%'
    if ratio not in (2, 3):
        return {'error': 'ratio'}
    if mode == 'standard':
        for ch in text:
            if ch not in std:
                return {'error': 'char', 'char': ch}
        enc = text
    else:
        punct = {'$': '/D', '%': '/E', '+': '/K', '/': '/O', '!': '/A', '"': '/B', '#': '/C', '&': '/F', "'": '/G',
                 '(': '/H', ')': '/I', '*': '/J', ',': '/L', ':': '/Z', ';': '%F', '<': '%G', '=': '%H', '>': '%I',
                 '?': '%J', '@': '%V', '[': '%K', '\\': '%L', ']': '%M', '^': '%N', '_': '%O', '`': '%W',
                 '{': '%P', '|': '%Q', '}': '%R', '~': '%S'}
        enc = ''
        for ch in text:
            o = ord(ch)
            if o > 127:
                return {'error': 'char', 'char': ch}
            if ch in punct:
                enc += punct[ch]
            elif 'a' <= ch <= 'z':
                enc += '+' + ch.upper()
            elif 1 <= o <= 26:
                enc += '$' + chr(o + 64)
            elif o == 0:
                enc += '%U'
            elif 27 <= o <= 31:
                enc += '%' + chr(o - 27 + 65)
            elif o == 127:
                enc += '%T'
            else:
                enc += ch
    count = len(enc) + 2
    return {'data': '*' + enc + '*', 'modules': count * (6 + 3 * ratio) + (count - 1)}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[('Z-9a+blot', 'standard', 2), {'error': 'char', 'char': 'a'}], [('café', 'standard', 2), {'error': 'char', 'char': 'c'}], [('café', 'standard', 4), {'error': 'ratio'}], [('ABPN/7PN/7', 'full', 1), {'error': 'ratio'}], [('a+ba+b', 'full', 4), {'error': 'ratio'}], [('café\t', 'full', 4), {'error': 'ratio'}], [('Z-9', 'standard', 4), {'error': 'ratio'}], [('café', 'standard', 3), {'error': 'char', 'char': 'c'}]], [[('lotZ-9', 'standard', 2), {'error': 'char', 'char': 'l'}], [('$5lot', 'standard', 2), {'error': 'char', 'char': 'l'}], [('', 'standard', 1), {'error': 'ratio'}], [('\x1blotlot', 'full', 2), {'data': '*%A+L+O+T+L+O+T*', 'modules': 207}], [('#1', 'full', 2), {'data': '*/C1*', 'modules': 64}], [('ABa+b', 'full', 2), {'data': '*AB+A/K+B*', 'modules': 129}], [('', 'full', 3), {'data': '**', 'modules': 31}], [('café', 'standard', 2), {'error': 'char', 'char': 'c'}]], [[('lot', 'standard', 3), {'error': 'char', 'char': 'l'}], [('12q*', 'standard', 3), {'error': 'char', 'char': 'q'}], [('a+bAB', 'full', 2), {'data': '*+A/K+BAB*', 'modules': 129}], [('#1café', 'standard', 4), {'error': 'ratio'}], [('ABPN/7Z-9', 'full', 2), {'data': '*ABPN/O7Z-9*', 'modules': 155}], [(' ', 'full', 1), {'error': 'ratio'}], [('$5 \x00', 'full', 2), {'data': '*/D5 %U*', 'modules': 103}], [('a+b', 'standard', 3), {'error': 'char', 'char': 'a'}]], [[('a+b\t', 'standard', 3), {'error': 'char', 'char': 'a'}], [('Z-9x$5', 'standard', 2), {'error': 'char', 'char': 'x'}], [('qPN/7café', 'full', 2), {'error': 'char', 'char': 'é'}], [('AB\x00 ', 'full', 1), {'error': 'ratio'}], [('*', 'full', 2), {'data': '*/J*', 'modules': 51}], [('AB12', 'standard', 2), {'data': '*AB12*', 'modules': 77}], [('\x7f\tlot', 'full', 3), {'data': '*%T$I+L+O+T*', 'modules': 191}], [('x12', 'standard', 2), {'error': 'char', 'char': 'x'}]], [[('a+bcafécafé', 'standard', 2), {'error': 'char', 'char': 'a'}], [('x', 'standard', 2), {'error': 'char', 'char': 'x'}], [('$5lot', 'full', 3), {'data': '*/D5+L+O+T*', 'modules': 175}], [('\x00', 'full', 1), {'error': 'ratio'}], [('', 'standard', 2), {'data': '**', 'modules': 25}], [('', 'standard', 1), {'error': 'ratio'}], [('\x7f\x00', 'full', 4), {'error': 'ratio'}], [('1250%lot', 'standard', 2), {'error': 'char', 'char': 'l'}]]]
labels = ["regression: standard mode lowercase", "repair trap", "combined fault", "control", "control", "boundary", "boundary", "control"]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (labels[i % len(labels)], i), 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: standard mode lowercase 0	`{'char': 'a', 'error': 'char'}`	`{'char': 'a', 'error': 'char'}`	Passed
repair trap 1	`{'char': 'c', 'error': 'char'}`	`{'char': 'c', 'error': 'char'}`	Passed
combined fault 2	`{'error': 'ratio'}`	`{'error': 'ratio'}`	Passed
control 3	`{'error': 'ratio'}`	`{'error': 'ratio'}`	Passed
control 4	`{'error': 'ratio'}`	`{'error': 'ratio'}`	Passed
boundary 5	`{'error': 'ratio'}`	`{'error': 'ratio'}`	Passed
boundary 6	`{'error': 'ratio'}`	`{'error': 'ratio'}`	Passed
control 7	`{'char': 'c', 'error': 'char'}`	`{'char': 'c', 'error': 'char'}`	Passed

SHA-256 / 31222c107a158e2511412b75c0400945844f167bb48cec5b95a2cb4a1a7dc123

Verification & scope

A deterministic bounded teaching model with a stipulated contract; it makes no claim of conformance to any published 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 2026-09-29T14:49:44.988769+00:00.

Case digest / d99f47ba97cd4331e8b5a001e12c3fc65eb2a97a58bcb6e099afd5e23a7eca34