为什么C ++编译器接受此初始化？静态整数x = x; [英] Why is this initialization accepted by the c++ compiler? static int x = x;

问题描述

我刚发现以下内容：

static int x = x;

为什么此初始化被C ++编译器接受？

Why is this initialization accepted by the C++ compiler?

我将其称为编译器异常，但可能有人对此有很好的解释。

I would call it a compiler anomaly, but someone might come with a good explanation for this.

因此对于具有静态存储的数据，可以进行初始化变量本身...我已经使用VS2015和VS2017编译器以及其他一些在线C ++编译器进行了尝试。

So for data with static storage, it is possible to initialize a variable with itself... I've tried this with a VS2015 and VS2017 compiler and also some other online C++ compilers.

推荐答案

对于 static 和非 static 变量，实际上是相同的。

It's actually the same for static and non-static variables.

名称在其声明器之后和初始化之前（如果有的话）立即可见。因此，在

A name becomes visible immediately after its declarator and before its initialization, if any. Thus in

static int x = x;

名称 x 在其名称后立即可见第一次出现，可以在初始化程序中引用。由于它是静态的，因此其初始值定义明确（ 0 ）。

the name x becomes visible immediately after its first occurrence, and can be referred to in the initializer. Since it's static, its initial value is well defined (it's 0).

这也是合法的，即使在块范围：

This is also legal, even at block scope:

int x = x;

尽管在这里您可能会收到警告，因为 x 正在使用其自己的不确定值进行初始化（大多数情况下行为未定义）。

although here you're likely to get a warning because x is being initialized with its own indeterminate value (the behavior is undefined in most cases).

这是一件很愚蠢的事情，但C ++并非如此竭尽全力阻止您做愚蠢的事情。例如，您可能想声明一个指向自身的指针：

It's a silly thing to do, but C++ isn't in the business of going out of its way to prevent you from doing silly things. As an example, you might want to declare a pointer that points to itself:

void *p = (void*)&p;

此处初始化程序是指 p 而不是它的值，但是必须使名称 p 可见才能使其正常工作。认为不应该添加特殊情况的规则。

Here the initializer refers to the address of p rather than its value, but the name p has to be visible to make that work. It wasn't considered worthwhile to add a special-case rule.

这篇关于为什么C ++编译器接受此初始化？静态整数x = x;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！