zaexage wrote:
>
> I got a 'class Manager' which contains a std::set of shared_ptr<Entity>;
> and 'class Entity' has a auto_ptr<StateMachine> as member
> and 'class StateMachine' needs shared_ptr<Entity> as member variable to
> access some functions outside.
>
> So, in order to break cyclic reference, I make the StateMachine to own a
> 'shared_ptr<Entity> const&', I think it's kind of reasonable.
>
I also use VS2008 with Python 2.5 and the boost libraries using the boost
consulting installer so it seems identical (which is strange).
I'd guess there's a simple typo somewhere. By using a const& to the
shared_ptr, it may be deallocated once the program (Python/C++) thinks the
original shared_ptr is not in use anymore. For example,
a = A()
a = B(a)
would be such a simple typo. A would immediately be deallocated but the
const ref in B wouldn't know.
A few comments:
* I assume each entity owns a unique StateMachine. Otherwise, the
auto_ptr<StateMachine> may be a problem. I've had many strange bugs from
using auto_ptr and thus I only use shared_ptr nowadays.
* You don't *need* a const& to break cyclic reference. Passing a shared_ptr
by value works too.
Example:
-------------------------------
// Forward Declare Entity
class Entity;
// Declare StateMachine
class StateMachine
{
StateMachine(shared_ptr<Entity> e) {...}
};
// Declare Entitity
class Entity
{
Entity(shared_ptr<StateMachine> s) {...}
};
--
View this message in context:
http://www.nabble.com/why-does-the-%22shared_ptr%3CX%3E-const-%22-silently-become-0xCCCCCCCC-tp22449314p22475430.html
Sent from the Python - c++-sig mailing list archive at Nabble.com.
_______________________________________________
Cplusplus-sig mailing list
Cplusplus-sig@python.org
http://mail.python.org/mailman/listinfo/cplusplus-sig
