TITLE: Typedefs are type aliases


PROBLEM: pj@sam.wpd.sgi.com (Paul Jackson), 2 Oct 92

I have some routines that pass around a couple of small integer
arguments, amongst other args.  I want to type these args so that
the compiler will warn if args of the wrong type are passed.  How
can I inhibit automatic promotion of other integer types, and get
a warning or error instead.

For example, what type (or other change) could I make (to) i1_t
and i2_t in the following so that the compiler would not silently
accept my passing a type i2_t to a function declared to expect a
type i1_t:

    typedef int i1_t;
    typedef int i2_t;
    
    extern void foo(i1_t);
    
    main(){
        foo(i2_t(1));       // wrong foo arg 1 type; but no warning
        return 0;
    }
    
    void foo(i1_t i){
        foo(i);
    }


RESPONSE: p j l @sparc10.cs.uiuc.edu (Paul Lucas), 3 Oct 92
          AT&T Bell Laboratories

*****>	You can't.  A typedef is *NOT* a new type: i1_t and 12_t are both
	int.