Issue with variant in record in array

[Jacek Laskowski 57]

Simple example:

 

program leak;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  FastMM4,
  System.SysUtils;


type
 TRx = record
        s : string;
        v : Variant;
      end;

 TAx = TArray<TRx>;

procedure Test;
var
  lA : TAx;
begin
  SetLength(lA, 3);
  lA[0].s := 'test2';
  lA[0].v := 888;
  lA[1].s := 'test1';
  lA[1].v := Now;
  lA[2].s := 'test3';
  lA[2].v := 'str';
end;

begin
  try
    Test;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.

When I don't assign TDateTime to a Variant field, the debugger shows the array and all records correctly, as in the picture on the left. And there is no leakage.

 

 

But when I assign TDateTime type to Variant field, as on the right side of the picture, the debugger does not show "plus" in hint window and I get a memory leak at the end.

 

What is wrong with this code?

 

 

[aehimself 388]

Do you get the same leak report if you don't debug the code, just let it to run?

It should not be the case, but try to call VarClear on the variant before exiting, and finalizing the array.

[Jacek Laskowski 57]

In fact, when I'm not debuging, there is no leak.
But is it an IDE error to show the record array (without the record expansion plus) in a hint debugger? Because I was afraid it was a problem in my record and array memory management. I do some tricks there.

[David Heffernan 2303]

When the debugger evaluates some variables to display values in the debugger it often leaks memory. This is a defect with the debugger. The code here does not leak. Any reported leaks are due the debugger. 

 

I see this very often with property getter functions that return strings. The debugger calls the function, creating a new string. But then the debugger fails to destroy the string. Leak. 

[David Heffernan 2303]

11 hours ago, aehimself said:

Do you get the same leak report if you don't debug the code, just let it to run?

It should not be the case, but try to call VarClear on the variant before exiting, and finalizing the array.

Not needed. Really not a great idea to suggest needless actions with no basis in fact. Just spreads FUD.