Possible D10.4.2 issue..

[balabuev 102]

11 minutes ago, Lajos Juhász said:

Sometimes it can result an Access Violation, it will cause no problem if in the meanwhile the handle is not used otherwise you cannot predict the result.

Prove it.

[Dalija Prasnikar 1396]

On 3/2/2021 at 4:27 AM, Ian Branch said:

    Unless someone can enlighten me otherwise, I suspect an issue here..

This sounds awfully familiar with this issue https://quality.embarcadero.com/browse/RSP-33140 

 

But this issue shows when VCL Styles are used.  Maybe something else got broken...

[Attila Kovacs 629]

48 minutes ago, balabuev said:

the subsequent CM_RELEASE message is ignored

Who by?

 

21 minutes ago, balabuev said:

Prove it.

It's a race condition, nothing to prove.

 

 

Not to mention that those implementations could change.

Edited March 3, 2021 by Attila Kovacs

[balabuev 102]

3 minutes ago, Attila Kovacs said:

Who by?

By Windows I guess. If some window becomes destroyed, all its pending messages are removed from the queue.

 

5 minutes ago, Attila Kovacs said:

It's a race condition

No. Unless you explicitly call Application.ProcessMessages [potentially] in a loop.

 

 

[Lajos Juhász 293]

35 minutes ago, balabuev said:

Prove it.

It's enough to insert anything between ShowModal and Free that will call an Application.ProcessMessages, for example to show another modal form and oops you get: 

Project Project1.exe raised exception class EInvalidPointer with message 'Invalid pointer operation'.

Something like:
 

procedure TForm1.Button1Click(Sender: TObject);
var x: TForm2;
    x2: TForm;
begin
  x:=TForm2.Create(nil);
  x2:=nil;
  try
    x2:=Tform2.Create(nil);
    if x.ShowModal=mrOk then
      x2.showmodal;
  finally
    x.free;
    x2.free;
  end;
end;

 

[balabuev 102]

2 minutes ago, Lajos Juhász said:

It's enough to insert anything between ShowModal and Free that will call an Application.ProcessMessages

 

Yes. You right. But the original code was:

with TLogInForm.Create(nil) do
try
  Result := ShowModal = mrOk;
finally
  Free;
end;