"Daniel P. Berrange" <berra...@redhat.com> writes: > On Thu, Oct 20, 2016 at 12:01:08PM +0100, Dr. David Alan Gilbert wrote: >> * Markus Armbruster (arm...@redhat.com) wrote: >> > "Dr. David Alan Gilbert" <dgilb...@redhat.com> writes: >> >> > > The problem is that our way of propagating errors actively discourages >> > > people from adding errors and you're left with lots of useless invented >> > > errno's. >> > > error_report makes it easy for people to scatter meaningful error >> > > messages >> > > in at any point. >> > > >> > > Make an easy, concise way of reporting an error that fits in with >> > > a propagation scheme and I'd consider converting stuff. >> > >> > error_setg(errp, "This is as simple as it gets, I'm afraid") >> > >> > Snark aside, I acknowledge the pain of converting call chains to >> > propagate Error objects, having converted "a few" myself. >> >> If you can get it down to that line it would be great! >> >> But unfortunately it isn't: >> a) I have to make sure my cleanup path after that error_setg doesn't >> cause any other errors because that breaks the rule >> that I can't call error_setg twice.
We disallowed setting a second error because that's a common symptom of forgotten or botched error handling. For what it's worth, g_error_set() does the same. >> b) I've got to put the whole local_err/error_propagate stuff all over. Only when you need to examine the errors you're propagating. >> c) We insist on allowing the Err ** pointer to be NULL that >> removes some potential simplifications. > > This last point is one i really dislike - if we could mandate that > the error parameters was non-NULL, it will eliminate alot of the > need to use local_err/error_propagate, as you could just check > if (*errp), and so largely solve (b). Outlawing null errp shifts the pain to the places that ignore errors. Whether that would be a win is not obvious. A patch doing the change might demonstrate it is, but it would be a lot of work, possibly for naught. For what it's worth, g_error_set() permits null, too.
