🚀 go-pugleaf

In article <42q81a$s2t@rdsunx.crd.ge.com>, volpe@bart.crd.ge.com says...
>
>Suppose I want the program to print out appropriate error messages? My 
>program becomes:
>
>What happens to your program?
>
>void manipulate_the_windows(Window *top)
>{
>  Window *A, *B, *C;
>
>  if (top != NULL) {
>    do_something_with_window(top);
>    A = get_subwindow(top);
>
>    if (A != NULL) {
>      do_something_different_with_window(A);
>      B = get_subwindow(A);
>
>      if (B != NULL) {
>        do_something_with_window(B);
>        C = get_subwindow(B);
>
>        if (C != NULL) {
>          /* All windows I'm looking for are good, so do it */
>          do_something_weird_with_four_windows(top,A,B,C);
>        }
>        else
>        {
>          printf("Error: C is NULL\n");
>        }
>      }
>      else
>      {
>        printf("Error: B is NULL\n");
>      }
>    }
>    else
>    {
>      printf("Error: A is NULL\n");
>    }
>  }
>  else 
>  {
>    printf("Error: Top is NULL\n");
>  }
>}
>
>Notice how the diagnostics grow further and further away from the test which
>causes them to be produced? 

Not necessarily.  Just change your if statements to check for invalid data:

void manipulate_the_windows(Window *top)
{
  Window *A, *B, *C;

  if (top == NULL) {
    printf("Error: Top is NULL\n");
  }
  else 
  {
    do_something_with_window(top);
    A = get_subwindow(top);

    if (A == NULL) {
      printf("Error: A is NULL\n");
    }
    else
    {
      do_something_different_with_window(A);
      B = get_subwindow(A);

      if (B == NULL) {
        printf("Error: B is NULL\n");
      }
      else
      {
        do_something_with_window(B);
        C = get_subwindow(B);

        if (C == NULL) {
          printf("Error: C is NULL\n");
        }
        else
        {
          /* All windows I'm looking for are good, so do it */
          do_something_weird_with_four_windows(top,A,B,C);
        }
      }
    }
  }
}

-- 
John Breckenridge                                Boothroyd Dewhurst, Inc.
johnb@dfma.com                                   all opinions are my own