Am 06.03.2013 um 16:38 hat Laszlo Ersek geschrieben: > On 03/06/13 16:19, Kevin Wolf wrote: > > Am 06.03.2013 um 16:04 hat Paolo Bonzini geschrieben: > >> Il 06/03/2013 15:46, Laszlo Ersek ha scritto: > >>>>> We could assert(!error_is_set(errp)) if we wanted. As soon as you've got > >>>>> an Error, you must return instead of calling more functions with the > >>>>> same error pointer. > >>> I think Luiz would suggest (*) to receive any error into a > >>> NULL-initialized local_err pointer; do the logic above on local_err, and > >>> just before returning, error_propagate() it to errp. > >>> > >>> (*) I hope you can see what I did there: if you disagree, you get to > >>> take that to Luiz, even though he didn't say anything. I'm getting > >>> better at working this list! :) > >> > >> I agree with Laszlo. > > > > I don't really understand the difference. As long as the function > > doesn't depend on the Error object to be present (which it doesn't), > > isn't it semantically exactly the same? > > The difference is when the caller passes in an already set Error. In > this case you release that and replace it with your own error. > > Usually we stick to the first error encountered. Under the above > suggestion you'd keep error handling internal to yourself, and in the > end make one attempt to propagate it outwards. If the caller has passed > in NULL, the error is dropped. If the caller's passed in a preexistent > error, then that one takes precedence and the new one is dropped (but it > doesn't interfere with the internal logic). Third, the caller can even > accept your error. > > error_propagate() and error_set() deal with the overwrite attempt > differently. The former silently drops the newcomer, whereas the latter > assert()s. > > Of course one wonders why a caller would pass in a preexistent Error.
Thanks, Laszlo, now I think I understand what Paolo and you were suggesting. However, I'd call any such caller buggy and don't feel like adding code so that it doesn't break. This is what I meant when I said you should return when you get an error, and not call other functions with the already used error pointer. Kevin
