委托会导致内存泄漏吗？ GC.TotalMemory(true) 似乎表明了这一点

Question

代码

using System;
internal static class Test
{
    private static void Main()
    {
        try
        {
            Console.WriteLine("{0,10}: Start point", GC.GetTotalMemory(true));
            Action simpleDelegate = SimpleDelegate;
            Console.WriteLine("{0,10}: Simple delegate created", GC.GetTotalMemory(true));
            Action simpleCombinedDelegate = simpleDelegate + simpleDelegate + simpleDelegate;
            Console.WriteLine("{0,10}: Simple combined delegate created", GC.GetTotalMemory(true));
            byte[] bigManagedResource = new byte[100000000];
            Console.WriteLine("{0,10}: Big managed resource created", GC.GetTotalMemory(true));
            Action bigManagedResourceDelegate = bigManagedResource.BigManagedResourceDelegate;
            Console.WriteLine("{0,10}: Big managed resource delegate created", GC.GetTotalMemory(true));
            Action bigCombinedDelegate = simpleCombinedDelegate + bigManagedResourceDelegate;
            Console.WriteLine("{0,10}: Big combined delegate created", GC.GetTotalMemory(true));
            GC.KeepAlive(bigManagedResource);
            bigManagedResource = null;
            GC.KeepAlive(bigManagedResourceDelegate);
            bigManagedResourceDelegate = null;
            GC.KeepAlive(bigCombinedDelegate);
            bigCombinedDelegate = null;
            Console.WriteLine("{0,10}: Big managed resource, big managed resource delegate and big combined delegate removed, but memory not freed", GC.GetTotalMemory(true));
            GC.KeepAlive(simpleCombinedDelegate);
            simpleCombinedDelegate = null;
            Console.WriteLine("{0,10}: Simple combined delegate removed, memory freed, at last", GC.GetTotalMemory(true));
            GC.KeepAlive(simpleDelegate);
            simpleDelegate = null;
            Console.WriteLine("{0,10}: Simple delegate removed", GC.GetTotalMemory(true));
        }
        catch (Exception e)
        {
            Console.WriteLine(e);
        }
        Console.ReadKey(true);
    }
    private static void SimpleDelegate() { }
    private static void BigManagedResourceDelegate(this byte[] array) { }
}

输出

GC.TotalMemory(true)
    105776: Start point
    191264: Simple delegate created
    191328: Simple combined delegate created
 100191344: Big managed resource created
 100191780: Big managed resource delegate created
 100191812: Big combined delegate created
 100191780: Big managed resource, big managed resource delegate and big combined delegate removed, but memory not freed
    191668: Simple combined delegate removed, memory freed, at last
    191636: Simple delegate removed

Answer 1

有趣的案例。这是解决方案：

组合委托是观察上纯粹的：看起来委托对外部来说是不可变的。但在内部，正在修改现有的代表。在某些情况下，出于性能原因，它们共享相同的_invocationList（针对少数代表连接到同一事件的场景进行优化）。不幸的是，simpleCombinedDelegate 的 _invocationList 引用了 bigMgdResDelegate，这导致内存保持活动状态。

Answer 2

我可能在这里忽略了要点，但是垃圾收集在设计上是不确定的。因此，由 .NET 框架决定何时回收内存。

您可以在一个简单的循环中运行 GC.GetTotalMemory 并获得不同的数字。也许不足为奇，因为文档指定返回的数字是一个近似值。