[C++-sig] why does the "shared_ptr<X> const&" silently become 0xCCCCCCCC

[ZaeX]

Thanks Roman,
I think I will take the advice to try working around this problem.

On Thu, Mar 12, 2009 at 1:17 PM, Roman Yakovenko
<roman.yakovenko at gmail.com>wrote:

> 2009/3/11 ZaeX <zaexage at gmail.com>:
> > Hi,Roman:
> >
> > I have tried adding call policy on my constructor, but I'm really no good
> at
> > this.
> > I have tried all the combinations below but none of them work:
> >
> > init<shared_ptr<A> const& >()[with_custodian_and_ward_postcall<0, 2> >()]
> > init<shared_ptr<A> const& >()[with_custodian_and_ward_postcall<1, 2> >()]
> > init<shared_ptr<A> const& >()[return_internal_reference<1,
> > with_custodian_and_ward<1, 2> >()]
> > init<shared_ptr<A> const& >()[return_internal_reference<1,
> > with_custodian_and_ward<0, 2> >()]
> >
> > Could you give some more advice on this?
> > P.S.:
> > I cannot modify the code back  to use shared_ptr by value here, I have to
> > break cyclic reference. And I think weak_ptr is no good idea, if I lock
> it
> > 60 times per second for each object, I guess it would be an impact on
> > performance.
>
> I don't know for sure, how to solve this problem. I can propose
> work-around, which may be will work for you.
> In your case, you have to keep shared_ptr<A> somewhere, until instance
> of B will die. So, you already do some kind of memory management.
>
> I suggest you to change your code as following:
> struct no_delete_a{
>    void operator(A*){}
> };
>
> class A{};
>
> class B
> {
> private:
>   shared_ptr<A> const m_ptr;
> public:
>    B(shared_ptr<A> const& ptr):m_ptr(ptr.get(), no_delete_a() )
> {cout<<m_ptr.get()<<endl;}
>   void ShowPtr(cout<<m_ptr.get()<<endl;)
> }
>
> In short to use "shared_ptr" custom deleter functionality.
>
> You don't hurt performance and can switch to use "shared_ptr by
> value"( and not to hurt your self :-) )
>
> HTH
>
> --
> Roman Yakovenko
> C++ Python language binding
> http://www.language-binding.net/
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