[boost] Re: [spirit] rule<> and copying

From: Eric Niebler (eric_at_[hidden])
Date: 2004-05-27 02:09:40

Joel de Guzman wrote:

> 
> Consider:
> 
>     rule<> a = x;
> 
> or:
> 
>     rule<> a;
>     a = x;
> 
> How should this behave if x is an int_p?

The int_p gets stored in an object on the heap, and the rule<> stores a 
shared_ptr to a polymorphic base.

> Now how should it behave if
> x is another rule? Consider a concrete example (snipped from the pascal
> parser):
> 
>     rule<> identifier;
>     rule<> fileIdentifier;
> 
>     identifier = ....
> 
>     fileIdentifier = identifier; // an alias
> 

The shared_ptr's reference count goes up. What's the problem?

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com