[boost] [Boost-bugs] [ boost-Bugs-832253 ] smart_ptr thread safe exception

From: SourceForge.net (noreply_at_[hidden])
Date: 2003-10-29 04:44:35

Bugs item #832253, was opened at 2003-10-29 09:44
Message generated for change (Tracker Item Submitted) made by Item Submitter
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=107586&aid=832253&group_id=7586

Category: smart_ptr
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: DA SILVA Antonio (adasilva)
Assigned to: Peter Dimov (pdimov)
Summary: smart_ptr thread safe exception

Initial Comment:
Hi,

Environment :
WindowsXP
boost 1_30_0
VC++6.0SP5

Context :
I am running tests on lot of allocations/assigns between 
two smart pointers shared by two threads.

Bug :
I receive a "bad_weak_ptr" exception in the method
sp_counted_base::add_ref() :

    void add_ref()
    {
#if defined(BOOST_HAS_THREADS)
        mutex_type::scoped_lock lock(mtx_);
#endif
        if(use_count_ == 0 && weak_count_ != 0) 
boost::throw_exception(boost::bad_weak_ptr());
        ++use_count_;
        ++weak_count_;
    }

Test program is like :
#include "boost/shared_ptr.hpp"

class CTest
{
public:
        CTest( )
        {
        }

        virtual ~CTest( )
        {
        }

        void dump( )
        {
                // do nothing.
        }
};

typedef boost::shared_ptr< CTest > CTestPtr;
CTestPtr ptr1;
CTestPtr ptr2;

// The class AThread is just a little wrapper around
// the "_beginthreadex" function call,
// it allows run/cancel/kill on threaded functions.

void thfn1( AThread *threadwrapper, void * )
{
        // Loop until the "threadwrapper" is cancelled.
        while( !threadwrapper->isCanceled( ) )
        {
                // Dummy work to access
                // concurrently the smart pointers...
                ptr1 = CTestPtr( new CTest );
                ptr1 = CTestPtr( new CTest );
                ptr1 = CTestPtr( new CTest );
                CTestPtr p1( ptr1 );
                CTestPtr p2( ptr2 );
                CTestPtr p3( ptr1 );
                CTestPtr p4( ptr1 );
                ptr1 = CTestPtr( new CTest );
                ptr1 = CTestPtr( new CTest );
                ptr1 = CTestPtr( new CTest );
                ptr1->dump( );
                ::Sleep( rand( ) % 10 );
        }
}

void thfn2( AThread *threadwrapper, void * )
{
        // Loop until the "threadwrapper" is cancelled.
        while( !threadwrapper->isCanceled( ) )
        {
                ptr2 = ptr1;
                ::Sleep( rand( ) % 5 );
                ptr2 = CTestPtr( new CTest );
                ptr2 = CTestPtr( new CTest );
                ptr2 = CTestPtr( new CTest );
                CTestPtr p1( ptr2 );
                CTestPtr p2( ptr2 );
                CTestPtr p3( ptr2 );
                CTestPtr p4( ptr2 );
                ptr2 = CTestPtr( new CTest );
                ptr2 = CTestPtr( new CTest );
                ptr2 = CTestPtr( new CTest );
                ::Sleep( rand( ) % 15 );
                ptr1 = ptr2;
        }
}

int main( int argc, char* argv[ ] )
{
        // You can chage the amount of threads
        // to throw the exception.
        const int nThreads = 12;

        AThread *tab[ nThreads ];

        // Create an array of threads.
        for( int i = 0; i < nThreads; i+=2 )
        {
                tab[ i ] = new AThread( thfn1 );
                tab[ i + 1 ] = new AThread( thfn2 );
        }

        // Start all the threads.
        for( i = 0; i < nThreads; ++i )
        {
                tab[ i ]->run( );
        }

        // Sleep during 5 minutes.
        ::Sleep( 300000 );

        // Ask the threads to cancel.
        for( i = 0; i < nThreads; ++i )
        {
                tab[ i ]->cancel( );
                tab[ i ]->join( );
                delete tab[ i ];
        }

        return 0;
}

I can give you a little project to test it.

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