将代理定义为函数指针 [英] Defining a delegate as a function pointer

问题描述

我正在使用一个调用非托管函数指针的委托。这将导致垃圾收集器在使用之前收集它，如MSDN上的CallbackOnCollectedDelegate MDA页面所述： CallbackOnCollectedDelegate MDA的MSDN页面。

分辨率表明我必须将适当的委托作为非托管函数指针进行编组。我的初始反应是使用：

  [MarshalAs（UnmanagedType.FunctionPtr）] 
 public delegate void EntityCallback（[MarshalAs （UnmanagedType.SysInt）] IntPtr实体）; 
  

但是，C＃编译器不会让我组织一个委托，即使这是建议的解决方案由MSDN。此外，MSDN页面仅显示一个被抛出的问题的示例，但不是其中一个解决方案。

如何将我的委托作为非托管函数指针进行编组或保留它是从GCed？

编辑：建议，我创建了回调的引用。因此，我的代码从/更改为：

  // From：
 foo.SetCallback（new EntityCallback（bar） ）; 
 
 // To：
 call = new EntityCallback（bar）; //在类
中引用参数foo.SetCallback（call）; 
  

现在这可以正常工作，但只能在调试模式下运行。当我切换到Release时，它会在同一时刻崩溃。为什么？

编辑2 ：更完整的代码段：

  public class Test 
 {
 private EntityCallback Call; 
 
 private void Bar（System.IntPtr target）
 {
 ... 
} 
 
 public Entity Foo {get;组; } 
 
 public Test（）
 {
 this.Foo = new Body.Sphere（）{Visible = false}; //不相关
 this.Foo.CollisionType = 3; //不相关
 
 this.Call = new EntityCallback（this.Bar）; 
 
 this.Foo.SetCallback（this.Call，EntityCallbackType.Collision）; 
} 
} 
  

解决方案

你没有正确读取它。您必须这样做：

...更改您的代码，以便在受管理端保留一个引用
给代理
$ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $
$ b

换句话说，只是存储对代理的引用在你的课堂中，确保课程对象能够持续足够长时间。如果你真的要使用静态。

I am using a delegate which calls an unmanaged function pointer. This causes the Garbage Collector to collect it before it is used, as described in the CallbackOnCollectedDelegate MDA page on MSDN: MSDN page for CallbackOnCollectedDelegate MDA.

The resolution states that I have to marshal the appropriate delegate as an unmanaged function pointer. My initial reflex was to use:

[MarshalAs(UnmanagedType.FunctionPtr)]
public delegate void EntityCallback([MarshalAs(UnmanagedType.SysInt)] IntPtr entity);

However, the C# compiler won't let me marshal a delegate, even if this is the suggested resolution by MSDN. Moreover, the MSDN page only shows an example of the problem being thrown, but not one of the resolution.

How could I marshal my delegate as an unmanaged function pointer or keep it from being GCed?

EDIT: As suggested, I created a reference of the callback. Therefore, my code changed from/to:

// From:
foo.SetCallback(new EntityCallback(bar));

// To:
call = new EntityCallback(bar); // Referenced in class
foo.SetCallback(call);

Now this does work - but only in Debug mode. When I switch to Release, it crashes at the same point. Why is that?

EDIT 2: More complete code snippet:

public class Test
{
    private EntityCallback Call;

    private void Bar(System.IntPtr target)
    {
        ...
    }

    public Entity Foo { get; set; }

    public Test()
    {
        this.Foo = new Body.Sphere() { Visible = false }; // Irrelevant
        this.Foo.CollisionType = 3; // Irrelevant

        this.Call = new EntityCallback(this.Bar);

        this.Foo.SetCallback(this.Call, EntityCallbackType.Collision);
    }
}

解决方案

You didn't read it correctly. You must do this:

...change your code to keep a reference to that delegate on the managed side for the lifetime of the marshaled unmanaged function pointer.

In other words, just store a reference to the delegate instance in your class and make sure the class object survives long enough. Use a static if you really have to.

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