Re: Registrar question... bug?

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

On Tuesday 01 June 2004 12:37, martin f krafft wrote:
> also sprach stephan beal <st...@s1...> [2004.06.01.1221 +0200]:
> > am i correct in thinking that the key 75 would never be registered,
> > because of this check in the ctor:
> >
> >         _S_reg() = _S_reg() || _Factory::register_builder(__KEY,
> > _M_builder);
>
> Yes, you are correct. It should probably be static.
>
> But then again, there's a problem because then it needs to be
> initialised, and since libfac is header-only...

Eeeek... i can see where this is heading. That's the reason that s11n's 
registration objects are in anonymous namespaces: to allow such 
initialization without ODR violations. i banged my head for days trying 
to figure that out, though. Maybe the Registrar should be moved into an 
anonymous namespace?

> I think I considered that and chose to make the builder non-static
> because the size overhead is zero and it's not like you'll create
> one million registrars for the same type combo. or?

i think you're right.

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.

> maybe, however, the initialisation of the default builder can be
> done in the macros?

i think it can only safely be done if it's in an anonymous namespace, 
otherwise ODR violations will (may?) become a problem. i had all kinds 
of headaches with this early on in s11n_CL's development. The anonymous 
namespaces, while not "pretty", offered a great solution - in fact, the 
only useful solution i know of.


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