Exception is swallowed in TCustomWSocket.ASyncReceive

[Fr0sT.Brutal 897]

Hi all,

spent some time just now on investigating a weird bug, it happened to be a memory AV that wasn't reported or caught by my exception handlers. Finally I came to see TCustomWSocket.ASyncReceive which appeared to just silently swallow any exceptions that happen in TriggerDataAvailable. I suppose it should have HandleBackGroundException(E) shouldn't it?

 

Ver.: 8.58

File: OverbyteIcsWSocket.pas

Line: 8427

Edited July 1, 2019 by Fr0sT.Brutal
addition

[Angus Robertson 519]

Does seem strange the code eats errors on OnDataAvailable silently while some other events do raise an exception.

 

I've updated my version to trigger a background exception, but this change is not absolutely backward compatible, applications that don't have OnBgException assigned will now shut down with an exception window, rather than perhaps continuing to ignore the error, maybe good, maybe bad.  This won't go into SVN for a few days, until I've rebuilt and tested all my applications.

 

Angus

 

[FPiette 363]

Why not put a try/except in you OnDataAvailable event handler?

 

[Fr0sT.Brutal 897]

Francois, of course this will do the trick but this means client code must meet some requirements which doesn't seem reliable to me.

Angus, well, have exceptions raised and shown could sound bad but it's really much better than have them swallowed silently IMHO. Unawareness of errors could cause mysterious AVs and other non-relative errors in random places. And all systems that claim to be robust should have bg exceptions handler already ¯\_(ツ)_/¯

[Angus Robertson 519]

The change to report exceptions rather than hide them is now in SVN.

 

Angus

 

[Fr0sT.Brutal 897]

Angus, just found that `bMore := FALSE` is still necessary... HandleBackGroundException calls OnException and stuff, then Abort is called, then socket is closed and then all these nested calls finish and... "while bMore do" loop continues :)))

[Angus Robertson 519]

Yes, should not have taken that out, we do need to break the loop, I'll put it back. 

 

However even that may not stop TriggerDataAvailable being called again since there may still be received data buffered,  Much nicer if there was no exception in the first place. 

 

Angus

[Fr0sT.Brutal 897]

Well, it's always better if no exceptions happen at all but the world isn't perfect )))