delphi – 为什么要使用FreeMem / Dispose例程来释放内存,但没有

如果我使用GlobalAllocPtr / HeapAlloc和GlobalFreePtr / HeapFree API,内存大小会减少.

这是我的测试代码：

type
  TMyRec = record
    Name: string;
    TickCount: Cardinal;
    Buf: array[0..1024 - 1] of byte;
  end;
  PMyRec = ^TMyRec;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormDestroy(Sender: TObject);
begin
  FList.Free;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  FList := TList.Create;
  ReportMemoryLeaksOnShutdown := true;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  i: Integer;
  Size: Integer;
  Rec: PMyRec;
  Heap: Cardinal;
begin
  Size := SizeOf(TMyRec);
  Heap := GetProcessHeap;
  for I := 0 to 2000 - 1 do
  begin
    Rec := AllocMem(Size);                              // Delphi routine
    //GetMem(Rec,Size);                                // Delphi routine
    //New(Rec);                                         // Delphi routine

    //Rec := GlobalAllocPtr(GPTR,Size);                // Windows API
    //Rec := HeapAlloc(Heap,HEAP_ZERO_MEMORY,Size);   // Windows API
    FList.Add(Rec);
  end;
end;

procedure TForm1.Button2Click(Sender: TObject);
var
  i: Integer;
  Size: Integer;
  Rec: PMyRec;
  Heap: Cardinal;
begin
  Size := SizeOf(TMyRec);
  Heap := GetProcessHeap;
  for i := FList.Count - 1 downto 0 do
  begin
    Rec := PMyRec(FList.Items[i]);
    FreeMem(Rec,Size);            // Delphi routine
    //Dispose(Rec);                // Delphi routine

    //GlobalFreePtr(Rec);          // Windows API
    //HeapFree(Heap,Rec);      // Windows API
  end;
  FList.Clear;
end;