Question

When I run my application in debug mode, sometimes I get a runtime error in this function:

void ChatListHandler::seatOccupancyChanged( const std::string& userName, bool occupied, bool isSelf, bool isSelfTable, int tableNo, int seatNo, int numPlayersAtTable )
{
    if(!isSelf && (isInGroup(userName,IN_GAME_GROUP) || isInGroup(userName,IN_LOBBY_GROUP)))
    {
        if(occupied)
        {
            movePlayer(userName,IN_GAME_GROUP);
        }
        else
        {
            movePlayer(userName,IN_LOBBY_GROUP);
        }
    }
}

bool ChatListHandler::isInGroup( const std::string& name, GroupTypeEnum group )
{
    for(size_t i = 0; i < m_groups.size(); ++i)
    {
        if(m_groups[i].second == group)
        {
            if(m_groups[i].first->getList())
            {
                for(agui::ListItem::iterator it = 
                    m_groups[i].first->getList()->getItemsBegin(); it !=
                    m_groups[i].first->getList()->getItemsEnd(); ++it)
                {
                    if((*it).first.text == name)
                    {
                        return true;
                    }
                }
            }

            break;
        }
    }

    return false;

    m_list->repositionGroups();
}

It crashes on:

if((*it).first.text == name)

I get:

Unhandled exception at 0x5fd1942c (msvcp90d.dll) in my.exe: 0xC0000005: Access violation reading location 0x00000040.

The call stack looks like:

Thanks

Answer 1

I can’t be sure without seeing all the code, but my guess is that there error has to do with these lines:

for(agui::ListItem::iterator it =
                m_groups[i].first->getList()->getItemsBegin(); it !=
                m_groups[i].first->getList()->getItemsEnd(); ++it)

Unless your call to getList() is always returning exactly the same list every time (that is, a pointer to the same list, not a copy), you could be getting iterators over different lists. This would mean that the check it != m_groups[i].first->getList()->getItemsEnd() would always be false, since the iterators come from different lists. In that case, your iterator could walk off the end of the list, so the dereference would cause a crash.

Hope this helps!