Cysharp/UniTask · error · ArgumentOutOfRangeException

minimumLength

Error message

minimumLength

What it means

Thrown by ArrayPool<T>.Rent(minimumLength) when minimumLength is negative. The pool sizes internal buckets by the requested length; a negative length is a programming error since no array can have negative size. This is UniTask's internal ArrayPool (mirrors System.Buffers.ArrayPool<T>) used for zero-allocation pooling.

Source

Thrown at src/UniTask/Assets/Plugins/UniTask/Runtime/Internal/ArrayPool.cs:38

        readonly SpinLock[] locks;

        ArrayPool()
        {
            // see: GetQueueIndex
            buckets = new MinimumQueue<T[]>[18];
            locks = new SpinLock[18];
            for (int i = 0; i < buckets.Length; i++)
            {
                buckets[i] = new MinimumQueue<T[]>(4);
                locks[i] = new SpinLock(false);
            }
        }

        public T[] Rent(int minimumLength)
        {
            if (minimumLength < 0)
            {
                throw new ArgumentOutOfRangeException("minimumLength");
            }
            else if (minimumLength == 0)
            {
                return EmptyArray;
            }

            var size = CalculateSize(minimumLength);
            var index = GetQueueIndex(size);
            if (index != -1)
            {
                var q = buckets[index];
                var lockTaken = false;
                try
                {
                    locks[index].Enter(ref lockTaken);

                    if (q.Count != 0)
                    {

View on GitHub (pinned to ceac8d6946)

Solutions

1. Clamp the value to zero before calling Rent: var len = Math.Max(0, computedLength);
2. Trace the upstream calculation that produced the negative value and fix the root cause.
3. Add a debug assertion or precondition check before the Rent call.

Example fix

// before
var buf = ArrayPool<byte>.Shared.Rent(estimatedSize - headerSize); // throws if headerSize > estimatedSize

// after
var len = Math.Max(0, estimatedSize - headerSize);
var buf = ArrayPool<byte>.Shared.Rent(len);

var safeLength = Math.Max(0, minimumLength);
var buf = ArrayPool<T>.Shared.Rent(safeLength);

When it happens

Trigger: Passing a computed negative value to ArrayPool<T>.Shared.Rent(). The pool is internal to UniTask but the guard is standard argument validation.

Common situations: A size calculation that subtracts from an uninitialized or incorrectly computed length, producing a negative result. An off-by-one in buffer sizing logic. Parsing external data that yields a negative count.

Related errors

• capacity
• EmptyQueue
• Delay does not allow minus delayFrameCount. dueTimeFrameCoun
• Delay does not allow minus periodFrameCount. periodFrameCoun
• Delay does not allow minus intervalFrameCount. intervalFrame

AI-assisted analysis of Cysharp/UniTask@ceac8d6946 (2026-08-13). Data as JSON: /api/errors/37f5c08579c3053c. Report an issue: GitHub.