7 replies to this topic

[manux]

Hey all,

I just came across a strange bug or abnormality, which took me half an hour of my time to find, and another to understand... During my program, I insert values in a map with types <int,FooBar*>.
At a certain point, I insert twice the same key, its supposed to be a normal thing, and the second key should be rejected and the first one kept intact.

Quote

Because map containers do not allow for duplicate key values, the insertion operation checks for each element inserted whether another element exists already in the container with the same key value, if so, the element is not inserted and its mapped value is not changed in any way.

It seems to do this. But sometime after, I need to call find() on this precise map to get a value. But the function never returns. It freezes my program do death whatever value I give to find(x)...

Did anyone already had this bug? Did I misunderstand something?

I solved the problem by checking myself if the value already wasn't in the map, but I had hoped that would be automatic.
I use MinGW g++, along with SDL and cPython but I don't think that would influence the stl. I also use windows.h for some parts of my program. Here are the responsable parts of my code:

    //the insertion part
    Player* newp = new Player;
    int pid=m_client->getNewPid();
    m_pmap.insert(std::pair<int,Player*>(pid,newp));
    //...
//later on
while (m_client->getDeadPlayers(&dead_player_id))//puts the id in this variable, returns false if queue is empty
{
    //...
    std::map<int,Player*>::iterator it = m_pmap.find(dead_player_id);
    //this line freezes
}

Edited by manux, 21 May 2009 - 03:59 AM.

[WingedPanther]

I'm not quite clear on what you mean. What compiler are you using, and can you post sample code?

[manux]

Sorry I forgot to mention it. I'll edit my first post.

[dargueta]

I think the problem might be with Windows...

In all seriousness: are you sure it's that line that's freezing, or your is while loop not exiting? What does m_client->getDeadPlayers() return?

[manux]

I checked getDeadPlayers seems ok,it empties a list a queries received from a server.

[dargueta]

But what does it return? If it always returns 1 or nearly always does, that could very well be your error.

[manux]

it doesn't, it works well I tested it multiple times. When I do the following it still looks like it blocks at map.find():

while (...)
{
fprintf(stdout,"before map.find\n");
fflush(stoud);
std::map<int,Player*>::iterator it = m_pmap.find(dead_player_id);
fprintf(stdout,"after map.find\n");
fflush(stoud);
}

the second line never gets printed and the program freezes, but it doesn't if I remove this single code line.

[dargueta]

Weird. Really weird. I'll see what I can dig up.