Re: Registrar question... bug?

[stephan b. <st...@s1...>]

On Tuesday 01 June 2004 14:16, martin f krafft wrote:
> What's the difference between what you want and what I do with the
> macros? The registrars are created in anonymous namespaces...
> aren't they?

namespace Factory
{
  template <typename _Key, typename _BaseType, typename _SubType = 
_BaseType,
            typename _Builder = Builder<_BaseType, _SubType> >
    class Registrar
    {
...



> I doubt you want the class to be in an anonymous namespace...

Perhaps not, but for s11n i had horrible problems with 
non-anonymous-namespace registrars and .hpp files. i kept getting ODR 
violations unless i was *really* careful with class registration 
placement.

> > My main concern is the possible end-user confusion when he
> > registers 2 keys for the same type. As a user i would expect the
> > LAST-run registration to take effect, but in fact only the
> > first-run registration would happen.
>
> So we should add an error policy, or figure out a way to make this
> a compiler error. like using static asserts. i'd like that the most.

That's an interesting idea. As a user i would expect to be able to 
register whenever i want, so i think a policy would be the better 
route. Or simply removing the static one-time check and taking the 
last-reg-takes-effect policy. i can't see a reason to keep people from 
changing the registrations at arbitrary times. That said, that's not 
something people will do, i think. In practice, i've never changed 
factories at runtime.



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