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

From: Robert Ramey (ramey_at_[hidden])
Date: 2004-07-12 11:54:25

I presume you are using serialization draft # 18 upload last april.  Since
then helpful users have found a couple of bugs which I have subsequently
fixed.  There is a more recent version that I have tested with boost 1.31 at
www.rrsd.com.  It is labeled serialization #20.

I am currently struggling - so far with only limited success - in getting
the most recent version of the serialization library checked in to the main
boost CVS.  This as been too slow to get it done but too fast to give up on.

Regarding your particular problem, I believe that this came up under the the
condition where a n object is saved through a pointer to its base class and
it was not registered or exported.  This has been addressed in the current
library by throwing an exception.  Of course this helps characterize the
problem - but it doesn't really fix the cause.  This latter one has to do
himself.

BTW, there have been a couple of other small bug fixes related to some
collections (hmm - map was among them!)- this might or might not address
your symptoms.  Another bug in the serialization of shared_ptr was uncovered
which was causing a memory leak.  I hope all this helps.

Thanks for the feedback.

As an aside - I notice that I'm getting about 300 downloads/month of the
serialization package from my web site.  I have no information about
downloads from the Yahoo/Boost files area - (which I would be curious to
know).  I get very little feedback - I'm wondering if lots of downloaders
take a look and decide it's too complex to actually use.

Robert Ramey

>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.

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

>Is it not possible to use a map of string/vector (the error seems to
>suggest the library failing when copying vector to map - eg ++use_count
>of the shared_ptr inside the TST).