[WIP] Check for memory leaks

csharp/Platform.Collections.Tests/ArrayTests.cs

@@ -1,3 +1,9 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Reflection;
+using System.Threading;
+using System.Threading.Tasks;
 using Xunit;
 using Platform.Collections.Arrays;
 
@@ -20,5 +26,157 @@ public void GetElementTest()
             Assert.False(array.TryGetElement(10, out element));
             Assert.Equal(0, element);
         }
+
+        [Fact]
+        public void ArrayPoolBasicFunctionalityTest()
+        {
+            var array1 = ArrayPool.Allocate<int>(10);
+            Assert.Equal(10, array1.Length);
+
+            ArrayPool.Free(array1);
+
+            var array2 = ArrayPool.Allocate<int>(10);
+            Assert.Equal(10, array2.Length);
+
+            // Should reuse the freed array
+            Assert.Same(array1, array2);
+        }
+
+        [Fact]
+        public void ArrayPoolMemoryLeakTest_UnboundedPoolGrowthFixed()
+        {
+            // This test verifies that the pool growth is now bounded (memory leak fixed)
+            var initialPoolCount = GetPoolCount<object>();
+
+            // Allocate arrays of many different sizes
+            for (long i = 1; i <= 1000; i++)
+            {
+                var array = ArrayPool.Allocate<object>(i);
+                ArrayPool.Free(array);
+            }
+
+            var finalPoolCount = GetPoolCount<object>();
+
+            // The pool should NOT have grown significantly (fix applied)
+            Assert.True(finalPoolCount <= ArrayPool.DefaultSizesAmount, 
+                $"Pool grew from {initialPoolCount} to {finalPoolCount} entries, but should be limited to {ArrayPool.DefaultSizesAmount}");
+        }
+
+        [Fact]
+        public void ArrayPoolMemoryLeakTest_ArrayContentNotCleared()
+        {
+            // This test verifies that array contents ARE cleared when returned to pool (fix applied)
+            var array = ArrayPool.Allocate<object>(5);
+            var testObject = new object();
+            array[0] = testObject;
+
+            ArrayPool.Free(array);
+
+            // Get the same array back from pool
+            var reusedArray = ArrayPool.Allocate<object>(5);
+            Assert.Same(array, reusedArray);
+
+            // The old object reference should be cleared (memory leak fixed)
+            Assert.Null(reusedArray[0]);
+        }
+
+        [Fact]
+        public void ArrayPoolMemoryLeakTest_PoolSizeLimited()
+        {
+            // This test verifies that pool size is now limited
+            var pool = new ArrayPool<object>(10, 5); // max 5 different sizes
+
+            // Allocate arrays of 10 different sizes
+            for (long i = 1; i <= 10; i++)
+            {
+                var array = pool.Allocate(i);
+                pool.Free(array);
+            }
+
+            var poolCount = GetInstancePoolCount(pool);
+
+            // Pool should be limited to 5 sizes maximum
+            Assert.True(poolCount <= 5, $"Pool has {poolCount} entries, should be limited to 5");
+        }
+
+        [Fact]
+        public void ArrayPoolMemoryLeakTest_ThreadStaticLeakage()
+        {
+            // This test demonstrates potential ThreadStatic memory leak
+            var initialThreadCount = GetActiveThreadCount();
+            var tasks = new List<Task>();
+
+            // Create multiple threads that use ArrayPool
+            for (int i = 0; i < 10; i++)
+            {
+                tasks.Add(Task.Run(() =>
+                {
+                    // Each thread creates its own ArrayPool instance via ThreadStatic
+                    var array = ArrayPool.Allocate<object>(100);
+                    ArrayPool.Free(array);
+
+                    // Clean up thread instance to prevent memory leak
+                    ArrayPool.ClearThreadInstance<object>();
+                }));
+            }
+
+            Task.WaitAll(tasks.ToArray());
+
+            // Force garbage collection to see if ThreadStatic instances are cleaned up
+            GC.Collect();
+            GC.WaitForPendingFinalizers();
+            GC.Collect();
+
+            // This test now demonstrates the fix for ThreadStatic cleanup
+        }
+
+        [Fact]
+        public void ArrayPoolThreadStaticCleanupTest()
+        {
+            // This test verifies that ClearThreadInstance works
+            // Use a custom ArrayPool instance to test the clear functionality
+            var pool = new ArrayPool<string>(10, 10);
+
+            var array = pool.Allocate(15);
+            pool.Free(array);
+
+            // Verify that the instance has entries
+            var poolCountBefore = GetInstancePoolCount(pool);
+            Assert.True(poolCountBefore > 0, $"Pool should have entries before cleanup, but had {poolCountBefore}");
+
+            pool.Clear();
+
+            var poolCountAfter = GetInstancePoolCount(pool);
+            Assert.Equal(0, poolCountAfter);
+        }
+
+        private static int GetPoolCount<T>()
+        {
+            // Use reflection to access the private _pool field to count entries
+            var threadInstanceProperty = typeof(ArrayPool<T>).GetProperty("ThreadInstance", 
+                BindingFlags.NonPublic | BindingFlags.Static);
+            var threadInstance = threadInstanceProperty.GetValue(null);
+
+            var poolField = typeof(ArrayPool<T>).GetField("_pool", 
+                BindingFlags.NonPublic | BindingFlags.Instance);
+            var pool = poolField.GetValue(threadInstance) as IDictionary<long, object>;
+
+            return pool?.Count ?? 0;
+        }
+
+        private static int GetInstancePoolCount<T>(ArrayPool<T> instance)
+        {
+            // Use reflection to access the private _pool field to count entries in a specific instance
+            var poolField = typeof(ArrayPool<T>).GetField("_pool", 
+                BindingFlags.NonPublic | BindingFlags.Instance);
+            var pool = poolField.GetValue(instance) as IDictionary<long, object>;
+
+            return pool?.Count ?? 0;
+        }
+
+        private static int GetActiveThreadCount()
+        {
+            return Process.GetCurrentProcess().Threads.Count;
+        }
     }
 }

csharp/Platform.Collections/Arrays/ArrayPool.cs

@@ -44,5 +44,13 @@ public static class ArrayPool
         /// <param name="array"><para>The array to be freed into the pull.</para><para>Массив который нужно освобоить в пулл.</para></param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static void Free<T>(T[] array) => ArrayPool<T>.ThreadInstance.Free(array);
+
+        /// <summary>
+        /// <para>Clears the thread-static instance for the current thread to prevent memory leaks.</para>
+        /// <para>Очищает экземпляр ThreadStatic для текущего потока, чтобы предотвратить утечки памяти.</para>
+        /// </summary>
+        /// <typeparam name="T"><para>The array elements type.</para><para>Тип элементов массива.</para></typeparam>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void ClearThreadInstance<T>() => ArrayPool<T>.ClearThreadInstance();
     }
 }

csharp/Platform.Collections/Arrays/ArrayPool[T].cs

@@ -33,15 +33,30 @@ public class ArrayPool<T>
         /// </summary>
         internal static ArrayPool<T> ThreadInstance => _threadInstance ?? (_threadInstance = new ArrayPool<T>());
         private readonly int _maxArraysPerSize;
-        private readonly Dictionary<long, Stack<T[]>> _pool = new Dictionary<long, Stack<T[]>>(ArrayPool.DefaultSizesAmount);
+        private readonly int _maxPoolSizes;
+        private readonly Dictionary<long, Stack<T[]>> _pool;
 
         /// <summary>
         /// <para>Initializes a new instance of the ArrayPool class using the specified maximum number of arrays per size.</para>
         /// <para>Инициализирует новый экземпляр класса ArrayPool, используя указанное максимальное количество массивов на каждый размер.</para>
         /// </summary>
         /// <param name="maxArraysPerSize"><para>The maximum number of arrays in the pool per size.</para><para>Максимальное количество массивов в пуле на каждый размер.</para></param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public ArrayPool(int maxArraysPerSize) => _maxArraysPerSize = maxArraysPerSize;
+        public ArrayPool(int maxArraysPerSize) : this(maxArraysPerSize, ArrayPool.DefaultSizesAmount) { }
+
+        /// <summary>
+        /// <para>Initializes a new instance of the ArrayPool class using the specified maximum number of arrays per size and maximum pool sizes.</para>
+        /// <para>Инициализирует новый экземпляр класса ArrayPool, используя указанное максимальное количество массивов на каждый размер и максимальное количество размеров пула.</para>
+        /// </summary>
+        /// <param name="maxArraysPerSize"><para>The maximum number of arrays in the pool per size.</para><para>Максимальное количество массивов в пуле на каждый размер.</para></param>
+        /// <param name="maxPoolSizes"><para>The maximum number of different sizes in the pool.</para><para>Максимальное количество разных размеров в пуле.</para></param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ArrayPool(int maxArraysPerSize, int maxPoolSizes) 
+        {
+            _maxArraysPerSize = maxArraysPerSize;
+            _maxPoolSizes = maxPoolSizes;
+            _pool = new Dictionary<long, Stack<T[]>>(maxPoolSizes);
+        }
 
         /// <summary>
         /// <para>Initializes a new instance of the ArrayPool class using the default maximum number of arrays per size.</para>
@@ -93,6 +108,17 @@ public Disposable<T[]> Resize(Disposable<T[]> source, long size)
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public virtual void Clear() => _pool.Clear();
 
+        /// <summary>
+        /// <para>Clears the thread-static instance for the current thread to prevent memory leaks.</para>
+        /// <para>Очищает экземпляр ThreadStatic для текущего потока, чтобы предотвратить утечки памяти.</para>
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void ClearThreadInstance()
+        {
+            _threadInstance?.Clear();
+            _threadInstance = null;
+        }
+
         /// <summary>
         /// <para>Retrieves an array with the specified size from the pool.</para>
         /// <para>Извлекает из пула массив с указанным размером.</para>
@@ -117,11 +143,25 @@ public virtual void Free(T[] array)
             {
                 return;
             }
+
+            // Check if we have too many different sizes, reject if pool is at capacity
+            if (!_pool.ContainsKey(array.LongLength) && _pool.Count >= _maxPoolSizes)
+            {
+                return;
+            }
+
             var stack = _pool.GetOrAdd(array.LongLength, size => new Stack<T[]>(_maxArraysPerSize));
             if (stack.Count == _maxArraysPerSize) // Stack is full
             {
                 return;
             }
+
+            // Clear array contents to prevent memory leaks from object references
+            if (!typeof(T).IsValueType)
+            {
+                Array.Clear(array, 0, array.Length);
+            }
+
             stack.Push(array);
         }
     }