Can't free after malloc

nusstu · #1 20-Apr-2005, 10:17

I've the following code which creates a 2-D array.
How do i free it properly. apparently, my method of free gives
the error:
free(): invalid pointer 0x80f3080!

CPP / C++ / C Code:

   int ** array;
  array = (int **)malloc(2*sizeof(int *)); 
  array[0] = (int*) malloc (2 * 2 * sizeof(int)); 
  if (array[0] == NULL) exit (-1); 

  free(array[0]);
  free(array);

Thanks.

davekw7x · #2 20-Apr-2005, 10:28

Quote:

Originally Posted by nusstu

I've the following code which creates a 2-D array.
How do i free it properly.

That is the correct way. Just make sure you aren't changing the value of array or array[0] anywhere else in your program.

You could try testing with this:

CPP / C++ / C Code:

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

int main()
{

  int **array;
  array = malloc(2*sizeof(int *)); 
  printf("array    = %p\n", array);

  array[0] = malloc(2 * 2 * sizeof(int)); 
  printf("array[0] = %p\n", array[0]);

  if (array[0] == NULL) {
    free(array);
    return 1;
  }
  free(array[0]);
  free(array);
  return 0;

}

Now, if this works, but it doesn't work with your program (with other stuff between malloc() and free()), then put printf after each malloc() and printf before each free() statement to see the value of the pointer that you are giving to free() is the same that you got from malloc().

Regards,

Dave

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