GC.Collect() 没有立即收集? [英] GC.Collect() not collecting immediately?

问题描述

在聊天讨论过程中，我编写了这个控制台应用程序.

In the course of a discussion in chat, I wrote this console application.

using System;

class Program
{
    static void Main(string[] args)
    {
        CreateClass();
        Console.Write("Collecting... ");
        GC.Collect();
        Console.WriteLine("Done");
    }

    static void CreateClass()
    {
        SomeClass c = new SomeClass();
    }
}

class SomeClass
{
    ~SomeClass()
    {
        throw new Exception();
    }
}

结果:

Collecting... Done

Unhandled Exception: System.Exception: Exception of type 'System.Exception' was
thrown.
   at SomeClass.Finalize()

我原以为应用会在 Done 打印出来之前崩溃.

I would have expected the app to crash before Done was printed.

我不太关心如何制作它.我的问题是，为什么不呢?

I don't care much about how to make it. My question is, why doesn't it?

推荐答案

不能在单个垃圾收集过程中收集具有终结器的对象.这些对象被移动到 f-reachable 队列，并一直保留在那里直到调用终结器.只有在那之后，它们才能被垃圾收集.

Objects with finalizers cannot be collected within a single garbage collection procedure. Such objects are moved to f-reachable queue, and remain there until finalizers are called. Only after that they can be garbage-collected.

以下代码更好，但无论如何你都不应该依赖它:

Following code is better, but you should not rely on it anyway:

GC.Collect();
GC.WaitForPendingFinalizers();
GC.Collect();

另外，在终结器中抛出异常对我来说似乎太残忍了，即使是为了测试目的.

Also, throwing exceptions in finalizer seems too brutal for me, even for testing purposes.

另外，终结器的有趣副作用:如果在终结器中存储 this 引用(将其分配给某个静态变量).

Also, interesting side-effect of finalizers: an object with finalizer can still 'resurrect' itself (effectively prevent garbage collection of itself), if stores this reference in finalizer (assigns it to some static variable).

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