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Quick check on dynamic array deprecation and any resulting memory leaks

Posted on 2008-06-20
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Last Modified: 2010-04-05
A little information on how this program works:

Main winsock component waits for new connections.
When a new connection arrives it takes the dynamic  array holding all the connections and sets the length to one larger.(I.E. SetLength(ServerClients,TotalConnections + 1)). In the new space allocolated it creates a new winsock object to take the connections.(Shown below).

Now when the connection is closed I FreeAndNil() that spot in the dynamic array. So you may have (con1,con2,nil,con4). What I have done(also shown below) is first take the nil out of the array by moving the next one in the array down. You would then have (con1, con2, con4, con4). I then reset all tags and information to reorder the array to (con1, con2, con3, con4). Now that con4 isn't necessary I set the length down one.

Now I thought I would have to put a FreeAndNil() for the con4 but that just gives me errors. It works without it but I wonder if I'm leaking memory this way.

Any suggestions on how this could be done differently? Or if it's fine as it is?
procedure TForm1.Winsock1ConnectionRequest(ASender: TObject;

  requestID: Integer);

var

  CurrentClient : TClientWinsock;

begin

  Inc(TotalClients);

  SetLength(ServerClients,TotalClients);

  ServerClients[TotalClients - 1] := TClientWinsock.Create(Winsock1);

  CurrentClient := ServerClients[TotalClients - 1];

  CurrentClient.LocalPort := LocalPort;

  CurrentClient.Tag := TotalClients - 1;

  CurrentClient.Ping := 0;

  CurrentClient.IdleTime := 0;

  CurrentClient.CurrentUser := '';

  CurrentClient.ActiveWindow := '';

  CurrentClient.OnDataArrival := WinsockDataArrival;

  CurrentClient.OnClose := WinsockClose;

  CurrentClient.OnError := WinsockError;

  CurrentClient.Close;

  CurrentClient.Accept(requestID);

end;
 
 

procedure TForm1.WinsockClose(Sender: TObject);

var

  I,J,Max : Integer;

  CurrentClient : TClientWinsock;

begin

  CurrentClient := (Sender as TClientWinsock);

  CurrentClient.Close;

  J := CurrentClient.Tag;

  ComboBox1.Items.Clear;

  FreeAndNil(ServerClients[J]);

  Dec(TotalClients);

  For I := J To High(ServerClients) Do

    begin

    If I = High(ServerClients) Then

      begin

      SetLength(ServerClients,TotalClients);

      Break;

    end;

    ServerClients[I] := ServerClients[I + 1];

    //FreeAndNil(ServerClients[I + 1]);

    ServerClients[I].Tag := ServerClients[I].Tag - 1;

  end;

  For I := Low(ServerClients) To High(ServerClients) Do

    begin

    ComboBox1.Items.AddObject(ServerClients[I].RemoteHostIP,TObject(ServerClients[I].Tag));

  end;

  Panel2.Caption := '';

  Panel3.Caption := '';

  Panel4.Caption := '';

  Panel5.Caption := '';

  Panel6.Caption := '';

end;

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Question by:ThievingSix
  • 2
4 Comments
 
LVL 10

Assisted Solution

by:dinilud
dinilud earned 50 total points
ID: 21836400
i think , there is no memory leak.

you can check this with 'EurekaLog' or 'FastMM'
0
 
LVL 37

Assisted Solution

by:Geert Gruwez
Geert Gruwez earned 50 total points
ID: 21836573
why don't you use a TCollection with a descendant of TCollectionItem ?
0
 
LVL 2

Accepted Solution

by:
Ustin19 earned 400 total points
ID: 21837195
dinilud is on point: it is no memory leaks
(con1, con2, con3, con4) - is pointers to objects, when (con1, con2, con4, con4) reduces to (con1, con2, con4) pointer to con4 stores in element [2] and all right.
Error appears when you freeandnil con4 (!) at first step of loop and then use it's method ServerClients[I].Tag at next iteration :)
0
 
LVL 37

Expert Comment

by:Geert Gruwez
ID: 21837262
saves all the hassle with using a collection
no need to reorder
0

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