Thread: Arrays with pointers

Hi guys

Lets look at an example:

Code:

char *str[]={"hi", "all"};

This code creates an array of pointers to char, and makes the pointers point to the character arrays "hi" and "all", respectively. Now, my question is regarding the following code:

Code:

int intarr[2][2]={{1,2} , {3,4}};
int *intptr[]=intarr;

As you may know by now, the above code is completely wrong. My question is: Why is it wrong? Because in the first example with strings, the array of pointers to char point to character-arrays. In the second example, the pointers to integer point to integer-arrays.

Why is it that in the integer-case, I must specify that the pointers point to arrays of length 2 (i.e. int (*intptr)[2] is correct), while I do not have to do that in the string-case?

Best,
Niles.

I believe Salem answered this just recently. IIRC, he said the name of the array is a pointer to the first element of the array - you know that.

The address of the name of the array, is the value you need for a pointer to the whole array.

It's WAAAYYYY late, so I'm not sure if that's right, but try it.

This works, but isn't quite what I thought would work:

Code:

#include <stdio.h>
#include <stdlib.h>

int main() {
  int i; 

  int intarray[2][2]={{1,2}, {3,4}};
  int *pint=*intarray;

  printf("\n\nN1=%d, N2=%d, N3=%d", *(pint+0), *(pint+1), *(pint+2) );

  printf("\n\n\t\t\t     press enter when ready");

  i = getchar();
  return 0;
}

As you may know by now, the above code is completely wrong. My question is: Why is it wrong? Because in the first example with strings, the array of pointers to char point to character-arrays. In the second example, the pointers to integer point to integer-arrays.

No, in the first example, You have an array of pointer to char.
The type of array element is pointer to char.

Take string literals as anonymous char array which you can't modify and have static scope.

Code:

static char _0[ ]  = "hi";
static char _1[ ]  = "all";

char *str[]={ _0 , _1 };

>>That is also what my original post states.
You states the array of pointers to char point to character-arrays.
The type of str is array! It's not pointer! It's array initialization.

Originally Posted by Niels_M

Ok, I feel like this thread got de-railed totally. I really appreciate all the input so far, but it does not seem to be answers to my OP.

I still don't feel like I have gotten a clear answer, so if anybody would help, I would appreciate it very much.

They're still discussing your original issue.
I am not 100% sure of what the standard says, but so far as I see, there is simply no implicit conversion from int[][] to int*[].
I believe that the 1D array is simply a special case as it decays to a mere pointer. In the 2D case, it treats the right-hand side as an array (which does not decay).