[boost] Re: "memory access violation" in boost::serialization

From: Jeff Flinn (TriumphSprint2000_at_[hidden])
Date: 2004-07-12 10:07:01

"Dirk Griffioen" <d.griffioen_at_[hidden]> wrote in message
news:2505062E579A9B45888B70D9BCFB3C073BA8BD_at_ex03.hidomain...
> Hi,
>
> I encountered the following little problem:
>
> I would like to use the following datastructures with boost::serialize:
>
> struct Match {};
> typedef std::string Key;
> typedef tst< Match, Key > TernarySearchTree; //this one has a shared_ptr
>
> typedef std::vector< TernarySearchTree > Trees;
> typedef std::map< std::string, Trees > Symbols;
>
> I have defined some serialize overloads so saving goes fine, but when
> loading I get a "memory acces violation" inside the following code:
>
> {
>    boost::archive::text_iarchive ia(ifs);
>    ia >> symbols_;
> }
>
> More specific, inside <boost/serializiton/shared_count.hpp>
>
>     void add_ref_copy()
>     {
> #if defined(BOOST_HAS_THREADS)
>         mutex_type::scoped_lock lock(mtx_);
> #endif
>        ++use_count_;
>     }
>
> Which constructs a scoped_lock, and there, the "explicit
> scoped_lock(lightweight_mutex & m): m_(m)" seems to go wrong.

Actually you'll find that the this pointer is either NULL or invalid.

>
> What could be the reason? The more since all worked fine (saving and
> loading) when I used a simple vector of tst's.

The following changes to .../boost/serialization/shared_ptr.hpp should do
it:

change line 74: if(t) t->add_ref_copy();

and

comment out line 125: //    shared_ptr_access::weak_count(*t) = 0;

IIRC, line 125 is the primary culprit.

-----------------
Jeff Flinn
Applied Dynamics, International