Remy Lebeau (TeamB) wrote:
David wrote:


TList is just a list of memory pointers. You are responsible for managing
the lifetimes of any objects you add to the list. Since you are not freeing
the object in your code, they are leaked. You need to free them manually,
eg:

myList := TList.Create;
...
myList.Add(TCustomer.Create('Bill Gates', 123)); //Memory leak caused here;
myList.Add(TCustomer.Create('Steven Jobs', 456)); //Memory leak caused here
...
// add this!
for I := 0 to myList.Count-1 do begin
  TCustomer(myList[I]).Free;
end;
...
FreeAndNil(myList);

If you want the list to take ownership of the objects and free them automatically
for you, use a TObjectList instead, and set its OwnsObjects property to True
(which it is by default).

--
Remy Lebeau (TeamB)

Remy, out of interest, why did you use FreeAndNil?

I know what it does but isn't it enough to just free myList?

David Cox wrote:
Hello All,

I use an exception handler MadException that also reports on memory leaks (BTW, a great tool!). It is indicating I have a memory leak in the following program (example modified from the Delphi Basics site to illustrate the error). The memory leak reported occurs during the TCustomer.Create. I am using Delphi 10 Seattle.

Any ideas on what I am doing wrong?

Thanks!

unit Unit2;
interface
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;
 
type
  // The customer class definition
  TCustomer = class
    private
      // The data fields of this new class
      CustomerName   : String;
      CustomerNumber : Integer;
    public
      constructor Create(const CustomerName   : String;
                         const CustomerNumber : Integer);
  end;
 
  TForm2 = class(TForm)
    procedure FormCreate(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
 
  private
    myList : TList;
   end;
 var
  Form2: TForm2;
 
implementation
 
{$R *.dfm}
 
// Customer constructor
// --------------------------------------------------------------------------
constructor TCustomer.Create(const CustomerName   : String;
                             const CustomerNumber : Integer);
begin
  self.CustomerName   := CustomerName;
  self.CustomerNumber := CustomerNumber;
end;
 
 
// --------------------------------------------------------------------------
procedure TForm2.FormCreate(Sender: TObject);
var
  customer : TCustomer;
 
begin
  myList := TList.Create;
  myList.Add(TCustomer.Create('Bill Gates', 123));   //Memory leak caused here;
  myList.Add(TCustomer.Create('Steven Jobs', 456));  //Memory leak caused here
  FreeAndNil(myList);
end;
 
// --------------------------------------------------------------------------
procedure TForm2.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  Action:=caFree;
end;
 
end.