如果我定义C / C ++一个0大小的数组，会发生什么？ [英] What happens if I define a 0-size array in C/C++?

问题描述

只是好奇，如果我定义了一个长度为零的数组实际上发生了什么 int数组[0]; 在code？ GCC不出现任​​何提示。

Just curious, what actually happens if I define a zero-length array int array[0]; in code? GCC doesn't complain at all.

示例程序

#include <stdio.h>

int main() {
    int arr[0];
    return 0;
}

澄清

实际上，我想弄清楚，如果零长度数组初始化这种方式，而不是被指着像Darhazer的言论变长，优化了还是不行。

I'm actually trying to figure out if zero-length arrays initialised this way, instead of being pointed at like the variable length in Darhazer's comments, are optimised out or not.

这是因为我必须释放一些code OUT到野外，所以我想弄清楚，如果我要处理的情况下尺寸被定义为 0 ，它发生在一些code。与静态定义的 int数组[SIZE];

This is because I have to release some code out into the wild, so I'm trying to figure out if I have to handle cases where the SIZE is defined as 0, which happens in some code with a statically defined int array[SIZE];

实际上，我是惊讶，GCC不抱怨，这导致了我的问题。从我收到的答案，我相信没有一个警告主要是由于支持老code还没有被更新，新的[]语法。

I was actually surprised that GCC does not complain, which led to my question. From the answers I've received, I believe the lack of a warning is largely due to supporting old code which has not been updated with the new [] syntax.

由于我主要是想了解一下错误，我标记伦丁的答案正确（谢里夫的是第一个，但它并不完整） - 其他的人指明了尾填充结构，它的实际使用，而有关，不正是我一直在寻找。

Because I was mainly wondering about the error, I am tagging Lundin's answer as correct (Nawaz's was first, but it wasn't as complete) -- the others were pointing out its actual use for tail-padded structures, while relevant, isn't exactly what I was looking for.

推荐答案

这是数组不能有大小为零。

An array cannot have zero size.

ISO 9899：2011 6.7.6.2：

ISO 9899:2011 6.7.6.2:

如果除权pression是一个不断前pression，应当有一个值大于零。

If the expression is a constant expression, it shall have a value greater than zero.

以上文字既是一个普通数组为真（§1）和VLA（§5）。这是C标准的规范文本。编译器是不允许不同的方式实现它。

The above text is true both for a plain array (§1) and a VLA (§5). This is normative text in the C standard. A compiler is not allowed to implement it differently.

GCC -std = C99 -pedantic发出警告这一点。

gcc -std=c99 -pedantic gives a warning for this.

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