如果的Int32只是一个别名INT，如何能的Int32类使用int？ [英] If Int32 is just an alias for int, how can the Int32 class use an int?

问题描述

被浏览过 .NET框架参考源的.NET源$ C ​​$ C，只是为了好玩。并发现了一些我不明白。

有一个的 Int32.cs 的用C＃code文件的Int32 键入。不知怎的，这似乎很奇怪，我。如何在C＃编译器编译code为的Int32 键入？

 公共结构的Int32：IComparable的，IFormattable，IConvertible {
    内部INT m_value;    // ...
}
 

但不是这种非法在C＃中？如果 INT 只是一个的别名的的Int32 ，它应该失败，编译<一个HREF =htt​​p://msdn.microsoft.com/library/7b625z82.aspx>错误CS0523 ：

  

结构成员类型'struct1的struct2领域'会导致在结构布局一个周期。

有没有在编译器中一些魔法，还是我完全偏离了轨道？

解决方案

  

这不就是违法的C＃？如果INT只是别名的Int32应该失败，出现错误CS0523编译。有没有在编译一些魔法？

是的;错误是在编译器pssed故意燮$ P $。循环检查完全跳过，如果有问题的类型是一个内置型

通常这种事情是违法的：

 的struct {S S; INT I; }
 

在这种情况下，S的尺寸是不确定的，因为无论大小S，则它必须等于本身加上int的大小。有没有这样的规模。

 的struct {S S; }
 

在这种情况下，我们没有从中推断S的大小的信息。

 结构的Int32 {我的Int32; }
 

但在这种情况下，编译器知道提前时间 System.Int32 是四个字节，因为这是一个很特殊的类型。

顺便说一下，如何在C＃编译器（和，对于这个问题，该CLR）决定当一组结构类型是循环的细节是非常有趣。我会尝试在某个时候写一个博客文章。

Been browsing through .NET source code of .NET Framework Reference Source, just for fun of it. And found something I don't understand.

There is a Int32.cs file with C# code for Int32 type. And somehow that seems strange to me. How does the C# compiler compile code for Int32 type?

public struct Int32: IComparable, IFormattable, IConvertible {
    internal int m_value;

    // ... 
}

But isn't this illegal in C#? If int is only an alias for Int32, it should fail to compile with Error CS0523:

Struct member 'struct2 field' of type 'struct1' causes a cycle in the struct layout.

Is there some magic in the compiler, or am I completely off track?

解决方案

isn't this illegal in C#? If "int" is only alias for "Int32" it should fail to compile with error CS0523. Is there some magic in the compiler?

Yes; the error is deliberately suppressed in the compiler. The cycle checker is skipped entirely if the type in question is a built-in type.

Normally this sort of thing is illegal:

struct S { S s; int i; }

In that case the size of S is undefined because whatever the size of S is, it must be equal to itself plus the size of an int. There is no such size.

struct S { S s; }

In that case we have no information from which to deduce the size of S.

struct Int32 { Int32 i; }

But in this case the compiler knows ahead of time that System.Int32 is four bytes because it is a very special type.

Incidentally, the details of how the C# compiler (and, for that matter, the CLR) determines when a set of struct types is cyclic is extremely interesting. I'll try to write a blog article about that at some point.

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