#define ArrayLength(x)(sizeof(x)/sizeof(*(x)))是什么意思? [英] What does #define ArrayLength(x) (sizeof(x)/sizeof(*(x))) mean?

问题描述

这行到底是什么意思?

很明显，定义是什么，但我不明白为什么在分母处传递x的指针:

It is clear what define is, but I don't understand why is passing the pointer of x at the denominator:

#define ArrayLength(x) (sizeof(x)/sizeof(*(x)))

谢谢

推荐答案

分母

sizeof(*(x))

是数组中第一个元素的长度(以字节为单位).变量x是数组类型，它 衰减 指向数组开头的指针.星号(*)是解引用运算符，因此*(x)表示" x"指向的数据.

is the length of the first element in the array in bytes. The variable x is of an array type, and it decays to a pointer, pointing to the start of the array. The asterisk (*) is the dereference operator, so *(x) means "the data pointed to by x".

sizeof(x)

将sizeof运算符应用于数组类型.这样就给出了整个数组的长度(以字节为单位).

applies the sizeof operator to an array type. This gives the length of the entire array in bytes.

#define ArrayLength(x) (sizeof(x)/sizeof(x[0]))

这也许更容易阅读.

这篇关于#define ArrayLength(x)(sizeof(x)/sizeof(*(x)))是什么意思?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！