6.18. Arithmetic on void- and Function-Pointers
In GNU C, addition and subtraction operations are supported on pointers to
void and on pointers to functions. This is done by treating the
size of a void or of a function as 1.
A consequence of this is that sizeof is also allowed on void
and on function types, and returns 1.
The option -Wpointer-arith requests a warning if these extensions