C ++:数组长度的sizeof [英] C++: sizeof for array length

问题描述

假设我有一个名为 LengthOf(array) 的宏:

Let's say I have a macro called LengthOf(array):

sizeof array / sizeof array[0]

当我创建一个大小为 23 的新数组时，我不应该为 LengthOf 取回 23 吗?

When I make a new array of size 23, shouldn't I get 23 back for LengthOf?

WCHAR* str = new WCHAR[23];
str[22] = '';
size_t len = LengthOf(str); // len == 4

为什么len == 4?

UPDATE:我打错了，它是 WCHAR*，而不是 WCHAR**.

UPDATE: I made a typo, it's a WCHAR*, not a WCHAR**.

推荐答案

因为这里的str是指向指针的指针，而不是数组.

Because str here is a pointer to a pointer, not an array.

这是指针和数组之间的细微差别之一:在这种情况下，您的 指针 在堆栈上，指向已分配到其他地方(可能是堆)的 23 个字符的数组.

This is one of the fine differences between pointers and arrays: in this case, your pointer is on the stack, pointing to the array of 23 characters that has been allocated elsewhere (presumably the heap).

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