array [100] = {0}如何将整个数组设置为0？ [英] how does array[100] = {0} set the entire array to 0?

问题描述

编译器如何填充 char array [100] = {0}; 中的值？

解决方案

我想知道编译器是如何初始化的。 div>

这不是魔术。

此C代码的行为在C规范的第6.7.8.21节中描述（在线草图C spec ）：对于没有指定值的元素，编译器初始化指针NULL和算术类型为零（并递归地应用于聚合）。

这个代码在C ++中的行为在C ++规范的第8.5.1.7节中有描述（ C ++规范的在线草案）：编译器聚合 - 初始化没有指定值的元素。

此外，请注意，在C ++（但不是C）中，可以使用空的初始化器列表，使编译器聚合初始化数组的所有元素：

  char array [100] = {}; 
  

至于编译器在这样做时可能会生成什么样的代码，请看看这个问题：从数组0初始化的奇怪汇编

How does the compiler fill values in char array[100] = {0};? What's the magic behind it?

I wanted to know how internally compiler initializes.

解决方案

It's not magic.

The behavior of this code in C is described in section 6.7.8.21 of the C specification (online draft of C spec): for the elements that don't have a specified value, the compiler initializes pointers to NULL and arithmetic types to zero (and recursively applies this to aggregates).

The behavior of this code in C++ is described in section 8.5.1.7 of the C++ specification (online draft of C++ spec): the compiler aggregate-initializes the elements that don't have a specified value.

Also, note that in C++ (but not C), you can use an empty initializer list, causing the compiler to aggregate-initialize all of the elements of the array:

char array[100] = {};

As for what sort of code the compiler might generate when you do this, take a look at this question: Strange assembly from array 0-initialization

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