/* File: bad_pointers.c
This program uses pointers incorrectly.
It won't compile.
*/
#include <stdio.h>
main ()
{
int a = 1, b = 2, c = 3 ;
double x = 3.1, y = 3.2, z = 3.3 ;
/* pointer declarations */
int *ptr1, *ptr2 ;
double *dptr ;
/* Can't assign integer expressions to pointers */
ptr1 = a + 7 ;
ptr1 = 5 ;
/* Exception: you can assign zero to a pointer */
ptr1 = 0 ;
ptr1 = NULL ;
/* Can't assign double address to integer pointer */
ptr1 = &x ;
}
Output
% cc bad_pointers.c
accom: Error: bad_pointers.c, line 20: illegal combination of pointer and integer, op =
ptr1 = a + 7 ;
----------------^
accom: Error: bad_pointers.c, line 20: types : pointer to int versus int
ptr1 = a + 7 ;
----------------^
accom: Error: bad_pointers.c, line 21: illegal combination of pointer and integer, op =
ptr1 = 5 ;
------------^
accom: Error: bad_pointers.c, line 21: types : pointer to int versus int
ptr1 = 5 ;
------------^
accom: Error: bad_pointers.c, line 28: Left pointer in assignment must have all qualifiers of right and pointed to types must be compatible (or void) (ANSI 3.3.16.1)
ptr1 = &x ;
-------------^
accom: Error: bad_pointers.c, line 28: Illegal pointer combination: pointer to int versus pointer to double
ptr1 = &x ;
-------------^
%