[C++-sig] Re: Pyste bug with unnamed enums

[David Abrahams]

"Roman Yakovenko" <roman.yakovenko at actimize.com> writes:

> 	Hi. I found bug in Pyste.
>
> Description:
> In your code you have 2 unnamed enum definitions
>
> enum { SOME_CONST_1 = 32 };
> enum { SOME_CONST_2 = 46 };
>
> after running pyste on this code you will get 
>
> // Unique type for unnamed enums
> #ifndef PYSTE_UNIQUE_INT_DEFINED
> #define PYSTE_UNIQUE_INT_DEFINED
> template<int num>
> struct UniqueInt {
>    int v;
>    enum { value=num };
>    UniqueInt(int v_):
>        v(v_)
>    {}
>    operator int() const
>    { return v; }
> };
> #endif // PYSTE_UNIQUE_INT_DEFINED 
>
> generated twice ( if you generate your code to the same module ).
>
> The possible solution are: 
>  1. To ask David Abrahams how we should export unnamed enums (
>  defined within class and within some namespace ).

Name them.  If you can't name them, you can't export them.  You can't
even pass them through a function template:

  enum { x = 1 };

  template <class T>
  int f(T);

  int y = f(x);  // error

Sorry.

>  2. To use unnamed enums as global constants for enums defined within namespace.
>      To define new class attribute if enum defined within class.
>  3. To put definition of UniqueInt within BPL

:(

I don't really know what UniqueInt is supposed to do, but I don't
love it because it's not unique ;-)

 enum { x = 1 }
 enum { y = 1 }

 BOOST_STATIC_ASSERT((boost::is_same<UniqueInt<x>,UniqueInt<y> >::value));


-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com