Getting the location address of an object in Delphi 7

Question

I have the following code sequence:

program OverrideAfterConstructionEtc;

{$APPTYPE CONSOLE}

uses
  SysUtils, Classes;

type

TA = class( TInterfacedObject)
public
procedure AfterConstruction; override;
procedure BeforeDestruction; override;
protected
FDummyData: array[ 1 .. 1000 ] of longint;
end;

{ TA }

procedure TA.AfterConstruction;
var
    selfPtr: Pointer;
    selfInt: Integer;
    selfStr: string;
    size: Integer;
begin
    inherited AfterConstruction;
    selfPtr := Addr( self );
    selfInt := Integer( selfPtr );
    selfStr := IntToHex( selfInt, 8 );

    size := TA.InstanceSize;
    WriteLn( 'TA instance allocated at 0x', selfStr );
    WriteLn( 'TA size is ', size );


end;

procedure TA.BeforeDestruction;
var
    selfPtr: Pointer;
    selfInt: Integer;
    selfStr: string;

    size: Integer;

begin

    selfPtr := Addr( self );
    selfInt := Integer( selfPtr );
    selfStr := IntToHex( selfInt, 8 );

    WriteLn( 'Preparing to destroy TA instance allocated at 0x', selfStr );

    size := TA.InstanceSize;
    WriteLn( 'TA size is ', size );

    inherited BeforeDestruction;
end;

const
    maxDummy = 1000;
var
    a: TA;
    dummy: TList;
    iter : integer;

    dummies: array [ 1 .. maxDummy ] of TList;
begin

    // Simulate a set of allocations.

    for iter := 1 to maxDummy do
    begin
        dummy := TList.Create;
        dummies[ iter ] := dummy;
    end;

    // Allocate the object we want to track.
    a := TA.Create;

    // Release the simulated allocations.
    for iter := 1 to maxDummy do
    begin
        dummy := dummies[ iter ];
        dummies[ iter ] := nil;
        FreeAndNil( dummy );
    end;



    // Release the tracked object.

    FreeAndNil( a );

end.

Code output:

• TA instance allocated at 0x0012FF88
• Size TA - 4012 Preparing for Destruction
• TA instance allocated at 0x0012FF80
• Size TA - 4012

I do not understand the difference "I". Can you give me a hint? I expected the printed values ​​to be the same.

Answer 1

Selfin an instance method is an implicit argument and is a reference to the instance that received the method call. It is implemented as a pointer.

Addr , @; . Addr Self, , . , ; , Self; , , , , , .

, Self , , . , Self -, A -> B -> C A -> C, B A C. - , , .

Answer 2

:

type
  TA = class( TInterfacedObject)
  public
    procedure AfterConstruction; override;
    procedure BeforeDestruction; override;
  end;

procedure TA.AfterConstruction;
begin
  inherited;
  writeln('AfterConstruction=',integer(self));
  writeln('AfterConstruction=',integer(addr(self)));
end;

procedure TA.BeforeDestruction;
begin
  writeln('BeforeDestruction=',integer(self));
  writeln('BeforeDestruction=',integer(addr(self)));
  inherited;
end;

:

AfterConstruction=10731904
AfterConstruction=1245020
BeforeDestruction=10731904
BeforeDestruction=1245028

(self) ( 10731904), integer (addr (self)) .

addr (self) self, self.

( Alt-F2 ):

mov [esp],eax

, addr (self), , self.

Addr , , @self, integer (self) integer (addr (self)).

Addr (self), self, .