为何“stackalloc”关键字不能与属性的作用？ [英] Why does the 'stackalloc' keyword not work with properties?

问题描述

我最近写一些不安全code在C＃中，注意到这将产生一个语法错误：

 公众安全的类UnsafeByteStream
{
    公共UnsafeByteStream（INT容量）
    {
        this.Buffer = stackalloc字节[容量]
    }

    公共字节*缓冲区{获得; }
}
 

这样做的结果是：无效EX pression术语stackalloc'/;预计/}预计。然而，当我将这个第一次到当地现场，像这样：

 公共UnsafeByteStream（INT容量）
{
    字节*缓冲区= stackalloc字节[容量]
    this.Buffer =缓冲区;
}
 

那么有没有语法错误产生。

有一个原因，或者是一些与编译器？据我所知，指针型属性是不是所有的常见的，但我还是不明白为什么这是一个的语法的，而不是错误的语义的之一，承担什么是错的与code。

解决方案

stackalloc 的必须的是局部变量声明的一部分，<一个HREF =htt​​ps://msdn.microsoft.com/en-us/library/cx9s2sy4.aspx相对=nofollow>在文档讨论。<​​/ P>

  

在[stackalloc]关键字是只适用于局部变量的初始化的。下面code使编译器错误。

  INT *块;
//下面赋值语句会导致编译器错误。您
声明和初始化一个地方，只有当//可以使用stackalloc
// 变量。
块= stackalloc INT [100];
 

因此​​，它确实是一个语法错误;并拒绝 obj.Property = stackalloc .. 的形式。

（后来分配到一个属性是 - 未捕获 - 语义错误）

I was writing some unsafe code recently in C# and noticed this produces a syntax error:

public unsafe class UnsafeByteStream
{
    public UnsafeByteStream(int capacity)
    {
        this.Buffer = stackalloc byte[capacity];
    }

    public byte* Buffer { get; }
}

The result of this is: "Invalid expression term 'stackalloc' / ; expected / } expected". However, when I assign this first to a local field, like so:

public UnsafeByteStream(int capacity)
{
    byte* buffer = stackalloc byte[capacity];
    this.Buffer = buffer;
}

Then there is no syntax error produced.

Is there a reason for this, or is something up with the compiler? I understand that pointer-type properties are not all that common, but I still don't understand why this is a syntax error as opposed to a semantic one, assuming something's wrong with the code.

解决方案

stackalloc must be part of the local variable declaration, as discussed in the documentation.

The [stackalloc] keyword is valid only in local variable initializers. The following code causes compiler errors.

int* block;
// The following assignment statement causes compiler errors. You
// can use stackalloc only when declaring and initializing a local 
// variable.
block = stackalloc int[100];

As such it truly is a syntax error; and rejects the obj.Property = stackalloc .. form.

(The later assignment to a property is an - uncaught - semantic error.)

这篇关于为何“stackalloc”关键字不能与属性的作用？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！