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

From: Dirk Griffioen (d.griffioen_at_[hidden])
Date: 2004-07-13 06:31:03

Thanks Jeff,

Your solution works - with a little twist:

I took the solution from #20 (thanks Robert!) and now it loooks like:

  if(NULL != t.pi_)
    t.pi_->add_ref_copy();

I also outcommented line 125.

& now my app works fine!

We will, however, upgrade to #20 as soon as possible.

Regarding the little discussion: it might very well be the case that
uses find the library very usefull, without too many a problem. We
certainly do, for instance on windows 2k (vc71) and HP True64 (probably
gcc but I'm not sure).

We have a lot of platforms here (HP, AIX, SUN, VMS, AS400 and Mainframe
- with different versions of native compilers and/or gcc) and it is
likely we will port to those platforms. If there's an interest, it might
be possible to gather some figures.

Cheers, Dirk

-----Original Message-----
From: boost-bounces_at_[hidden]
[mailto:boost-bounces_at_[hidden]] On Behalf Of Jeff Flinn
Sent: maandag 12 juli 2004 17:07
To: boost_at_[hidden]
Subject: [boost] Re: "memory access violation" in boost::serialization

"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

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