[boost] Re: Re: Re:boost::serialization Remarks

From: Jeff Flinn (TriumphSprint2000_at_[hidden])
Date: 2004-05-06 12:23:23

Martin,

<martin.ecker_at_[hidden]> wrote in message
news:OFDC881632.ACC5C7EF-ONC1256E8C.00370B68-C1256E8C.00375AC8_at_tab.at...
> Jeff,
>
> > Although, I am having problems with my
> > VC71 MFC application reporting memory
> > leaks of a 24byte block corresponding
> > to each shared_ptr loaded from an
> > oarchive.
>
> You probably mean "loaded from an iarchive".

I certainly did.

> Anyway, due to the modifications I've made in
> our local code base of boost::serialization
> I had a bit of a look through the code.
>
> I'm not sure, but the memory leaks you experience
> could possibly be related to the fact that
> basic_iarchive::delete_created_pointers is never
> called.
> Maybe you can add a call to this function yourself
> somewhere in your application (delete_created_pointers
> is a public member function of basic_iarchive)
> and see if the memory leaks disappear.
> Note that this is just a guess on my part,
> as I haven't had time to look at all the code
> in detail.

I've tried this with both the example and with my actual code, but end up in
an infinite loop in the scoped_lock constructor in
boost::detail::sp_counted_base::release, when the shared_ptr is destroyed.
I've instrumented my class constructors/destructors and can see that the
proper number of constructions/desctructions take place. So I don't think
basic_iarchive::delete_created_pointers is the problem here.

I'm trying to track down where the memory is allocated, but vc debugger is
not cooperating. It's only reporting the block number, which of course is
different each time I run. So I can't do a break and get the actual location
the allocation is occuring.

> In reference to the example you posted, you
> could change it to not use an empty shared_ptr
> but actually allocate an object for it
> and then change the deserialization code to:
>
> if( lIn.good() )
> {
>   boost::archive::xml_iarchive ia( lIn );
>
>   ia & boost::serialization::make_nvp( "SomeClass", lSomeClass );
>   ia.delete_created_pointers();
> }

Using the fix you previously posted for
boost::serialization::shared_ptr_access

    static void add_ref_copy(boost::detail::sp_counted_base * t){
        if(t) t->add_ref_copy();
    };

Fixed the NULL shared_ptr access violation I was seeing.

Thanks, Jeff