c - 下面声明的类型不应是不完整类型的声明是什么意思

Question

C 标准规定:

If the declaration of an identifier for an object is a tentative definition and has internal linkage, the declared type shall not be an incomplete type

“声明的类型不应是不完整的类型”是什么意思？

Answer 1

这意味着您不能拥有:

static int arr[]; // This is illegal as per the quoted standard.
int main(void) {}

数组 arr 是暂时定义的，类型不完整(缺少关于对象大小的信息)，也有内部链接(static 说 arr 有内部链接)。

鉴于以下(在文件范围内)，

int i; // i is tentatively defined. Valid.

int arr[]; // tentative definition & incomplete type. A further definition 
           // of arr can appear elsewhere. If not, it's treated like
           //  int arr[] = {0}; i.e. an array with 1 element.
           // Valid.

有效。