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warren.bare@gmail.com · Guest

Hi Folks,

I reproduced a very simple memory leak problem below. Basically, I
have a global TStringList object. Periodically I make a new string
list, then free the global object and point the global object at the
newly created string list.

This leaks memory.

Check it out in the simple example below. All you need is a form with
a timer on it that calls the routine every few seconds. My my real
app, the does not happen as often, but the principle is the same.

When you run this, you will see the task manager memory usage go up by
a little bit every time the function fires.

Memory experts please help. What's the deal here???????????

Thanks,
Warren

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls,
Forms,
Dialogs, ExtCtrls, StdCtrls;

type
TForm1 = class(TForm)
Timer1: TTimer;
procedure Timer1Timer(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;
slGlobal: TStringList;

implementation

uses
Math;

{$R *.dfm}

procedure TForm1.Timer1Timer(Sender: TObject);
var
slTmp: TStringList;
begin
slTmp:= TStringList.Create;

while slTmp.Count < 10000 do
begin
// simulate a data string with random text
slTmp.Add(
StringOfChar(Chr(RandomRange(32,64)), RandomRange(10,30)) +
StringOfChar(Chr(RandomRange(32,64)), RandomRange(10,30)) +
StringOfChar(Chr(RandomRange(32,64)), RandomRange(10,30))
);
end;

// If i Just free slTmp, there is not leak, but if I free
// the slGlobal, then point slGlobal at slTmp, I get a leak

slGlobal.Free;
slGlobal := slTmp;
end;

end.

Nicholas Sherlock · Guest

[email]warren.bare (AT) gmail (DOT) com[/email] wrote:

warren.bare@gmail.com · Guest

Hmmmm. OK, I did not know that about the task manager at all. That
probably explains some other weirdness i have seen also.

Sorry for asking what may seem like a glaringly obvious question, but
how do I monitor real memory usage.

Nicholas Sherlock · Guest

[email]warren.bare (AT) gmail (DOT) com[/email] wrote:

etherington19@aol.com · Guest

Hi Warren B
I've used the following bit of code to track memory whilst developing.
PosMessage is simply a note of where the app was when I called this
proc. I think I found this stuff on About Delphi.

procedure LogMemory(PosMessage: string);
var
MS: TMemoryStatus;
begin
MS.dwLength := SizeOf(MemoryStatus);
GlobalMemoryStatus(MS);

Form1.EventLog(Format('%8s %8s %-s', [DateToStr(Date),
TimeToStr(Now),
PosMessage + ' ' + FormatFloat('#,###" KB"', MS.dwAvailPhys div
1024)]));

end;

Ron Etherington