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rodrigogiraoserraorodrigogiraoserrao
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Add configurable fail-safe controls to brainfuck interpreter (#104)
- add a fail-safe settings card with configurable timeout, tape length limit, and a disable toggle - persist fail-safe preferences in localStorage and apply them on load - enforce the configurable guard rails during program execution with clearer error reporting ------ [Codex Task](https://chatgpt.com/codex/tasks/task_e_69514885fabc8325a1f8cd2e84dcac95)
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Lines changed: 116 additions & 14 deletions

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‎brainfuck-interpreter.html‎

Lines changed: 116 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -168,6 +168,34 @@ <h2 style="margin: 0;">Output</h2>
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</div>
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</div>
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</section>
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<section class="surface tool-card">
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<div class="card-header">
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<h2 style="margin: 0;">Fail-safe settings</h2>
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<p style="margin: 0; color: var(--tx-2); max-width: 48ch;">Prevent runaway programs by stopping execution after a
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time limit or when the tape grows too large.</p>
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</div>
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<div class="content-flow" style="--flow-space: 0.75rem;">
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<label class="content-flow" style="--flow-space: 0.25rem;">
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<span>Timeout (seconds)</span>
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<input id="failsafe-timeout" type="number" min="0" step="1" value="3" style="max-width: 200px;">
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<small class="input-help">Stops execution after this many seconds. Use 0 for no timeout.</small>
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</label>
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<label class="content-flow" style="--flow-space: 0.25rem;">
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<span>Tape length limit (cells)</span>
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<input id="failsafe-tape-limit" type="number" min="0" step="1" value="0" style="max-width: 200px;">
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<small class="input-help">Interrupts execution if the tape exceeds this length. Use 0 to allow unlimited
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growth.</small>
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</label>
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<label style="display: inline-flex; gap: 0.5rem; align-items: center;">
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<input id="failsafe-disabled" type="checkbox">
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<span>Disable the fail-safe entirely</span>
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</label>
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</div>
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</section>
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</main>
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<script src="https://cdn.jsdelivr.net/npm/codemirror@5.65.15/lib/codemirror.min.js"></script>
@@ -184,6 +212,9 @@ <h2 style="margin: 0;">Output</h2>
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const bfInput = document.getElementById('bf-input');
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const inputHelp = document.getElementById('input-help');
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const asciiModeRadio = document.getElementById('mode-ascii');
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const failsafeTimeoutInput = document.getElementById('failsafe-timeout');
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const failsafeTapeLimitInput = document.getElementById('failsafe-tape-limit');
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const failsafeDisabledInput = document.getElementById('failsafe-disabled');
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const textarea = document.getElementById('code-input');
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const editor = CodeMirror.fromTextArea(textarea, {
@@ -195,11 +226,17 @@ <h2 style="margin: 0;">Output</h2>
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});
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const STORAGE_KEY = 'brainfuck-interpreter-code';
198-
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class BrainfuckTimeoutError extends Error {
229+
const FAILSAFE_STORAGE_KEY = 'brainfuck-interpreter-failsafe-settings';
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const DEFAULT_FAILSAFE_SETTINGS = {
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timeoutSeconds: 3,
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tapeLengthLimit: 0,
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disabled: false,
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};
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class BrainfuckFailSafeError extends Error {
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constructor(message, debugInfo) {
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super(message);
202-
this.name = 'BrainfuckTimeoutError';
239+
this.name = 'BrainfuckFailSafeError';
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this.debugInfo = debugInfo;
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}
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}
@@ -333,7 +370,54 @@ <h2 style="margin: 0;">Output</h2>
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return `${leftEllipsis ? '… ' : ''}${cells.join(' ')}${rightEllipsis ? ' …' : ''}`;
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}
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336-
function runProgram(program, inputs) {
373+
function getStoredFailsafeSettings() {
374+
try {
375+
const raw = localStorage.getItem(FAILSAFE_STORAGE_KEY);
376+
if (!raw) return { ...DEFAULT_FAILSAFE_SETTINGS };
377+
const parsed = JSON.parse(raw);
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return sanitizeFailsafeSettings(parsed);
379+
} catch (error) {
380+
return { ...DEFAULT_FAILSAFE_SETTINGS };
381+
}
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}
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function sanitizeFailsafeSettings(settings) {
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const timeoutSeconds = Number.isFinite(settings.timeoutSeconds)
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? Math.max(0, Math.floor(settings.timeoutSeconds))
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: DEFAULT_FAILSAFE_SETTINGS.timeoutSeconds;
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const tapeLengthLimit = Number.isFinite(settings.tapeLengthLimit)
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? Math.max(0, Math.floor(settings.tapeLengthLimit))
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: DEFAULT_FAILSAFE_SETTINGS.tapeLengthLimit;
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const disabled = Boolean(settings.disabled);
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return { timeoutSeconds, tapeLengthLimit, disabled };
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}
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function persistFailsafeSettings(settings) {
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try {
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localStorage.setItem(FAILSAFE_STORAGE_KEY, JSON.stringify(settings));
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} catch (error) {
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// Ignore persistence errors and continue.
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}
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}
403+
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function applyFailsafeSettings(settings) {
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failsafeTimeoutInput.value = settings.timeoutSeconds;
406+
failsafeTapeLimitInput.value = settings.tapeLengthLimit;
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failsafeDisabledInput.checked = settings.disabled;
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}
409+
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function collectFailsafeSettingsFromInputs() {
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const settings = sanitizeFailsafeSettings({
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timeoutSeconds: Number(failsafeTimeoutInput.value),
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tapeLengthLimit: Number(failsafeTapeLimitInput.value),
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disabled: failsafeDisabledInput.checked,
415+
});
416+
persistFailsafeSettings(settings);
417+
return settings;
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}
419+
420+
function runProgram(program, inputs, failsafeSettings) {
337421
const commands = program.replace(/[^\>\<\+\-\.\,\[\]]/g, '');
338422
const jumpMap = buildJumpMap(commands);
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@@ -342,17 +426,21 @@ <h2 style="margin: 0;">Output</h2>
342426
let inputIndex = 0;
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let ip = 0;
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const output = [];
345-
const timeoutMs = 3000;
429+
const timeoutMs = failsafeSettings.timeoutSeconds * 1000;
346430
const startTime = performance.now();
347431

432+
function enforceFailSafe(message) {
433+
const debugInfo = [
434+
`Tape length: ${tape.length}`,
435+
`Pointer position: ${pointer}`,
436+
`Tape window: ${formatTapeWindow(tape, pointer)}`,
437+
].join('\n');
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throw new BrainfuckFailSafeError(message, debugInfo);
439+
}
440+
348441
while (ip < commands.length) {
349-
if (performance.now() - startTime > timeoutMs) {
350-
const debugInfo = [
351-
`Tape length: ${tape.length}`,
352-
`Pointer position: ${pointer}`,
353-
`Tape window: ${formatTapeWindow(tape, pointer)}`,
354-
].join('\n');
355-
throw new BrainfuckTimeoutError('Execution timed out after 3 seconds.', debugInfo);
442+
if (!failsafeSettings.disabled && failsafeSettings.timeoutSeconds > 0 && performance.now() - startTime > timeoutMs) {
443+
enforceFailSafe(`Execution timed out after ${failsafeSettings.timeoutSeconds} second${failsafeSettings.timeoutSeconds === 1 ? '' : 's'}.`);
356444
}
357445

358446
const instruction = commands[ip];
@@ -391,6 +479,10 @@ <h2 style="margin: 0;">Output</h2>
391479
}
392480
break;
393481
}
482+
483+
if (!failsafeSettings.disabled && failsafeSettings.tapeLengthLimit > 0 && tape.length > failsafeSettings.tapeLengthLimit) {
484+
enforceFailSafe(`Execution stopped because the tape exceeded ${failsafeSettings.tapeLengthLimit} cell${failsafeSettings.tapeLengthLimit === 1 ? '' : 's'}.`);
485+
}
394486
ip += 1;
395487
}
396488

@@ -418,11 +510,11 @@ <h2 style="margin: 0;">Output</h2>
418510
const mode = asciiModeRadio.checked ? 'ascii' : 'numbers';
419511
const inputs = parseInputs(bfInput.value, mode);
420512
const program = editor.getValue();
421-
const output = runProgram(program, inputs);
513+
const output = runProgram(program, inputs, collectFailsafeSettingsFromInputs());
422514
renderOutput(output);
423515
updateStatus(`Program ran successfully. Output length: ${output.length} byte${output.length === 1 ? '' : 's'}.`);
424516
} catch (error) {
425-
const debugDetails = error instanceof BrainfuckTimeoutError && error.debugInfo
517+
const debugDetails = error instanceof BrainfuckFailSafeError && error.debugInfo
426518
? `${error.message}\n\nDebug info:\n${error.debugInfo}`
427519
: error.message;
428520
updateStatus(debugDetails, true);
@@ -464,6 +556,16 @@ <h2 style="margin: 0;">Output</h2>
464556
document.getElementById('mode-numbers').addEventListener('change', updateInputHelp);
465557
updateInputHelp();
466558

559+
applyFailsafeSettings(getStoredFailsafeSettings());
560+
[failsafeTimeoutInput, failsafeTapeLimitInput].forEach((input) => {
561+
input.addEventListener('input', () => {
562+
collectFailsafeSettingsFromInputs();
563+
});
564+
});
565+
failsafeDisabledInput.addEventListener('change', () => {
566+
collectFailsafeSettingsFromInputs();
567+
});
568+
467569
const initialStatus = programFromHash !== null
468570
? 'Loaded program from URL and saved to local storage.'
469571
: hadStoredProgram

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