Need help investigating an app crash

[Cristian Peța 122]

20 hours ago, Lars Fosdal said:

Proper stack traces with EurekaLog, MadExcept or similar, are invaluable in such cases.

I second this.

On 7/29/2025 at 10:25 AM, Der schöne Günther said:

As for (3), my app was able to log the following callstack:

24/07/2025 14:31:32
[63.4]
Thread-ID 9052 ("TIdThreadWithTask")EAccessViolation: "Access violation at address 0098638C in module 'MyStuff.exe'. Write of address 00000004"
[0098638C] IdTask.TIdTask.DoBeforeRun
[00CA9106] JclHookExcept.DoExceptFilter
[00CA92D9] JclHookExcept.HookedExceptObjProc
[0040BAA3] System.@HandleAnyException
[004E2399] System.Classes.ThreadProc
[0040C6F8] System.ThreadWrapper

Here I don't see line number in IdTask.TIdTask.DoBeforeRun. I suppose it is the first line. Also the call stack is not what it should.

I would like also assembler code and register values.

Address 00000004 is FBeforeRunDone in TIdTask.DoBeforeRun.

  TIdTask = class(TObject)
  protected
    FBeforeRunDone: Boolean;
  ....
  end;

procedure TIdTask.DoBeforeRun;
begin
  FBeforeRunDone := True; <-- "Access violation at address 0098638C in module 'MyStuff.exe'. Write of address 00000004"
  BeforeRun;
end;

So a reference to TIdTask object is nil but we don't see the call stack to know who is calling this nil reference.

A proper call stack is missing.

[Der schöne Günther 340]

I usually have very good callstacks (using the FastMM4_FullDebugMode.dll), except these rare cases when I don't.

 

I have never bothered with other tools like madExcept because I thought they would output the same anyway. If something corrupts the stack (which is what Windows indicates), then I'm not sure how much of a valid callstack could have been recovered anyway.