零长度数组 [英] zero length arrays

问题描述

最近我碰到一个结构定义来了，

Recently I came across a structure definition,

struct arr {
    int cnt;
    struct {
        int  size;
        int *name;
    } list[0];
};

，现在我不知道的原因列表[0] 正在申报。我所感兴趣的是，这是为什么使用。它有什么优势？如果有，是什么呢？

and now I don't know the reason for list[0] being declared. What I am interested in is why is this used. Does it have any advantage? If yes, what is it?

推荐答案

使用是动态长度的数组。您可以使用分配内存的malloc（），并有阵居住在该结构的末尾：

The use is for dynamic-length arrays. You can allocate the memory using malloc(), and have the array reside at the end of the structure:

struct arr *my_arr = malloc(sizeof *my_arr + 17 * sizeof *my_arr->list);
my_arr->cnt = 17;
my_arr->list[0].size = 0;
my_arr->list[1].name = "foo";

实际上能够对长度使用0（如在注释中指出）一个GCC扩展。在C99，你可以离开了大小一共面值为同样的效果。

Actually being able to use 0 for the length is (as pointed out in a comment) a GCC extension. In C99, you can leave out the size literal altogether for the same effect.

在这些事情的顺利实施，你经常看到这个为1的长度做了，但分配复杂一点，因为你必须计算所需要的内存时补偿。

Before these things were implemented, you often saw this done with a length of 1, but that complicates the allocation a bit since you must compensate when computing the memory needed.

这篇关于零长度数组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！