pointers - To what use is multiple indirection in C++? -

under circumstances might want use multiple indirection (that is, chain of pointers in foo **) in c++?

most common usage @aku pointed out allow change pointer parameter visible after function returns.

#include <iostream>  using namespace std;  struct foo {     int a; };  void createfoo(foo** p) {     *p = new foo();     (*p)->a = 12; }  int main(int argc, char* argv[]) {     foo* p = null;     createfoo(&p);     cout << p->a << endl;     delete p;     return 0; } 

this print

12 

but there several other useful usages in following example iterate array of strings , print them standard output.

#include <iostream>  using namespace std;  int main(int argc, char* argv[]) {     const char* words[] = { "first", "second", null };     (const char** p = words; *p != null; ++p) {         cout << *p << endl;     }      return 0; }