Handling Exceptions raised from inside a thread

[chronozphere]

Hey guys,

At this moment, I'm looking at threads more closely and it seemed to me that before you deploy threads at a large scale in your application, you have to think about how to trap and handle exceptions.

First, I'm not a fan of this:


procedure TSubsystemThread.Execute;
begin
try
//do your stuff here
except //eat all exceptions
end;
end;

IMHO, this is one of the most awfull things you can do to yourself (programming-wise that is ;) ), as you make it really hard to find errors later on.

So I was looking at a better solution and found this (2nd example on page):
http://edn.embarcadero.com/article/10452

What strikes me here, is that to make the mechanism work, you make a call to ExceptObject(), which seems to access global exception information. I might be nitpicking here, but is this thread-safe?

Having said that, isn't the following solution alot better?


procedure TMyThread.Execute;
begin
FException := nil;
try
// raise an Exception
raise Exception.Create('I raised an exception');
except
on E: Exception do
HandleException(E); //Pass exception object to handler, and then to form
end;
end;

procedure TMyThread.HandleException(ExceptionObject: Exception);
begin
FException := ExceptionObject;
try
// Don't show EAbort messages
if not (FException is EAbort) then
Synchronize(DoHandleException);
finally
FException := nil;
end;
end;


Does anyone have experience with this? Seems like an obligatory question every programmer has to answer before starting to get serieus with threads.

Thanks!

[farcodev]

for my part my help is pretty limited, sorry :( , the last time i used thread it wasn't w/o exception management

oops excepted i used the awful form :o

[chronozphere]

Can someone else shed any light on this? There must at least be some do's and don'ts on this subject, I suppose.