周期的结构布局不存在 [英] Cycle in the struct layout that doesn't exist

问题描述

这是我的一些代码的简化版本：

This is a simplified version of some of my code:

public struct info
{
    public float a, b;
    public info? c;

    public info(float a, float b, info? c = null)
    {
        this.a = a;
        this.b = b;
        this.c = c;
    }
}

问题是误差结构成员信息导致在结构布局周期。像值类型的行为结构后我。我可以模拟这种使用类和克隆成员函数，但我不明白为什么我应该需要。

The problem is the error Struct member 'info' causes a cycle in the struct layout. I'm after struct like value type behaviour. I could simulate this using a class and a clone member function, but I don't see why I should need to.

这是怎么回事错误真的吗？递归或许会永远的建设在一些类似的情况，但我想不出任何方式，它能够在这种情况下。 。下面举例说明了应该是罚款，如果该程序将汇编

How is this error true? Recursion could perhaps cause construction forever in some similar situations, but I can't think of any way that it could in this case. Below are examples that ought to be fine if the program would compile.

new info(1, 2);
new info(1, 2, null);
new info(1, 2, new info(3, 4));

编辑：

edit:

我使用的解决方案是使信息一类，而不是一个结构，给它一个成员函数返回的，我路过时，它使用的复印。实际上模拟相同的行为作为一个结构，但有一类。

The solution I used was to make "info" a class instead of a struct and giving it a member function to returned a copy that I used when passing it. In effect simulating the same behaviour as a struct but with a class.

我还创建了以下问题，同时寻找一个答案。

I also created the following question while looking for an answer.

值类型的类定义？

推荐答案

这是不合法的拥有包含自身作为成员的结构。这是因为结构具有的固定尺寸​​，然后它必须至少为每个成员的大小的总和一样大。你的类型就必须有8个字节的两个浮筒，至少有一个字节，以显示是否信息为空，加上另一个的尺寸信息。这给了下面的不等式：

It's not legal to have a struct that contains itself as a member. This is because a struct has fixed size, and it must be at least as large as the sum of the sizes of each of its members. Your type would have to have 8 bytes for the two floats, at least one byte to show whether or not info is null, plus the size of another info. This gives the following inequality:

 size of info >= 4 + 4 + 1 + size of info

这显然是不可能的，因为它需要你的类型是无限大的。

This is obviously impossible as it would require your type to be infinitely large.

您必须使用引用类型（即类）。你可以让你的类不可变的，覆盖等于和的GetHashCode 给价值类似的行为，类似于字符串类。

You have to use a reference type (i.e. class). You can make your class immutable and override Equals and GetHashCode to give value-like behaviour, similar to the String class.

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