macros - C++: sizeof for array length

Question

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

sizeof array / sizeof array[0]

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

Why does len == 4?

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

Answer 1

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

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).