Question

A brief question to do mainly with understanding how pointers work with arrays in this example:

char *lineptr[MAXLENGTH]

Now I understand this is the same as char **lineptr as an array in itself is a pointer.

My question is how it works in its different forms/ de-referenced states such as:

lineptr
*lineptr
**lineptr
*lineptr[]

In each of those states, whats happening, what does each state do/work as in code?

Any help is much appreciated!

Answer 1

Now I understand this is the same as char **lineptr as an array in itself is a pointer.

No, an array is not the same as a pointer. See the C FAQ: http://c-faq.com/aryptr/index.html.

lineptr

This is the array itself. In most situations, it decays into a pointer to its first element (i.e. &lineptr[0]). So its type is either int *[MAXLENGTH] or int **.

*lineptr

This dereferences the pointer to the first element, so it’s the value of the first element (i.e. it’s the same as lineptr[0]). Its type is int *.

**lineptr

This dereferences the first elements (i.e. it’s the same as *lineptr[0]). Its type is int.

*lineptr[]

I don’t think this is valid syntax (in this context).