What's the meaning of multiple const qualifiers?

Question

Code:

const char* const* const* foo(int bar);

I've seen double consts before which prevent the modification of the pointer too. First time i've seen triple const in my life. Wondering what its use is.

Answer 1

In your example all but the top level of indirection all const qualified.

const char            /* const qualified base level */
    *const            /* const qualified level 1 */
    *const            /* const qualified level 2 */
    *                 /* regular level 3 */
    foo(int bar);

foo is a function that accepts an int argument and returns a regular pointer.
The pointer it returns points to a const qualified pointer
which, in turn, points to another const qualified pointer
which points to const qualified char

Answer 2

If you have a multilevel pointer, you have several pointer variables. Example:

char*** foo;

is accessed like this:

| foo | pointer1 | pointer2 | string |
   |    ^     |    ^     |    ^
    \___/      \___/      \___/

You can qualify each of the four locations in memory as being const, as in the declaration

const char *const *const *const foo;

However, best avoid becoming a three star programmer.