Alocates allocation memory for a multi-level pointers

**PuKa** · 10-07-2011

good evening everybody, when i try to understand deep about constant pointer, pointer to constant, raise on with multi-level pointer, i got trouble.

Code:

#include <iostream>
using namespace std;
int main() {
  /*  const int*** a; // ->**a is a pointer level 1
  int** b; // ->*b is a pointer level 1
  **a = *b;
  */
  int x = 2;
  int* y = &x;
  int** z = &y;
  int*** t = &z;
  int**** k = &t;
  const int*** b = new const int**;
  **b = ***k;
  cout << "k before changed: " << ****k << ", " << "*y = x = " << *y;

  /*  const int**** a = &t;
  int*** b;
  ***a = **b;
  */
  //  a = b;
  return 0;
}

When i try to compile this code no error occur, but when runs executable file, output: segmentation fault.

Thanks for any repy.

**PuKa** · 10-07-2011

Dose nobody help me?. this code is just i want to test about multi-level pointer, i'm sorry about my bad english, but i really spent a lot of time for this problem. thanks a lot.

**Elysia** · 10-07-2011

Be patient.

>>**b = ***k;
b points to a const int**, but the value pointed to is undefined, hence you can't dereference it.

b --> undefined value
*b = undefined value
**b = undefined behavior (can't derefernce undefined value)

**Salem** · 10-07-2011

Give us chance!
Response time can be anywhere between minutes and 24 hours, depending on who's online at the time. It's a 24 hour world, people come and go at all times.

> **b = ***k;
Before you do **b, you need to make *b actually point at something useful.

**laserlight** · 10-07-2011

Originally Posted by PuKa

when i try to understand deep about constant pointer, pointer to constant, raise on with multi-level pointer, i got trouble.

I suggest that you limit yourself to two levels of indirection, which in fact would have been sufficient to demonstrate your problem. I won't begrudge you wanting to reach for a third level of indirection to test yourself, but honestly four levels of indirection is going overboard.

**PuKa** · 10-07-2011

Thanks a lot. i understood, really beautiful , i feels crazy now.

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