Re: Warning about int<-->enum conversions?

[Nicholas Nethercote <njn25 at cam dot ac dot uk>]

I'm seeing conflicting responses about the legality of these conversions:


On Thu, 8 Jul 2004, Giovanni Bajo wrote:

> > Does GCC have a flag that would make it give warnings if an enum
> > value is mixed up with an int?  Like this:
> >
> >     void f ( int );
> >
> >     typedef enum { AA, BB, CC } T;
> >
> >     f (AA)           -- complain please
> >     int x = CC;      -- ditto
>
> No, because this is a kind of integer promotion which is allowed by the
> standard ([conv.prom]/2), so there is nothing wrong about it. Converting the
> other way (int -> enum) is instead forbidden and should be rejected by GCC.


On Thu, 8 Jul 2004, Gabriel Dos Reis wrote:

> In C, you can have both implicit conversions. C++ says that you can't go 
> from int to enums implicitly

Who's right?  Hmm... maybe you both are, I didn't actually specify whether 
this was C or C++ (it was meant to be C).

The reason I asked is that apprently Harbison & Steele (C: A Reference 
Manual) say:

  "In fact, some UNIX C compilers implement a weakly typed form of
  enumerations in which some conversions between enumerated types and
  integers are not permitted without casts"

N