malloc_in_function.c

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


void malloc_in_function(char **myArray, int size)
{
  int i = 0;

  *myArray = (char *) malloc(size * sizeof(char));
  if (*myArray == NULL)
  {
    fprintf(stderr, "Error allocating memory for myArray!\n");
    exit(0);
  }

  /* this is how to access array members in the function */
  for (i = 10; i < 20; i++)
  {
    /* This line will cause a segmentation fault. Why? */
      /* *myArray[i] = 'a' + (i - 10); */

    /* This line works much better. */
    (*myArray)[i] = 'a' + (i - 10);
  }
}

int main(int argc, char **argv)
{
  /* char myArray[20]; */
  char *myArray;
  int size = 20;
  int i = 0;

  malloc_in_function(&myArray, size);

  for (i = 0; i < 10; i++)
  {
    myArray[i] = 'A' + i;
  }
    
  for (i = 0; i < 20; i++)
  {
    printf("myArray[%d] = %c\n", i, myArray[i]);
  }

  free(myArray);
}

/* in main(), what does (myArray + 10) and &myArray[10] have in common?
 * What about *(myArray + 10) and myArray[10]?
 * What is *myArray + 10? Is it the same as myArray[0] + 10?
 * If the malloc was for an int, would (myArray + 10) be the same as &myArray[10]?
 */