I'm confused. Are you saying that that program always raised RuntimeError, or that it started raising RuntimeError with the new behavior (3.3 alpha 2)?
On Tue, Apr 3, 2012 at 2:47 PM, Maciej Fijalkowski <fij...@gmail.com> wrote: > On Sat, Mar 31, 2012 at 7:45 PM, R. David Murray <rdmur...@bitdance.com> > wrote: >> >> On Sun, 01 Apr 2012 03:03:13 +1000, Nick Coghlan <ncogh...@gmail.com> >> wrote: >> > On Sun, Apr 1, 2012 at 2:09 AM, Guido van Rossum <gu...@python.org> >> > wrote: >> > > Here's a different puzzle. Has anyone written a demo yet that provokes >> > > this RuntimeError, without cheating? (Cheating would be to mutate the >> > > dict from *inside* the __eq__ or __hash__ method.) If you're serious >> > > about revisiting this, I'd like to see at least one example of a >> > > program that is broken by the change. Otherwise I think the status quo >> > > in the 3.3 repo should prevail -- I don't want to be stymied by >> > > superstition. >> > >> > I attached an attempt to *deliberately* break the new behaviour to the >> > tracker issue. It isn't actually breaking for me, so I'd like other >> > folks to look at it to see if I missed something in my implementation, >> > of if it's just genuinely that hard to induce the necessary bad timing >> > of a preemptive thread switch. >> >> Thanks, Nick. It looks reasonable to me, but I've only given it a quick >> look so far (I'll try to think about it more deeply later today). >> >> If it is indeed hard to provoke, then I'm fine with leaving the >> RuntimeError as a signal that the application needs to add some locking. >> My concern was that we'd have working production code that would start >> breaking. If it takes a *lot* of threads or a *lot* of mutation to >> trigger it, then it is going to be a lot less likely to happen anyway, >> since such programs are going to be much more careful about locking >> anyway. >> >> --David >> _______________________________________________ >> Python-Dev mailing list >> Python-Dev@python.org >> http://mail.python.org/mailman/listinfo/python-dev >> Unsubscribe: >> http://mail.python.org/mailman/options/python-dev/fijall%40gmail.com > > > Hm > > I might be missing something, but if you have multiple threads accessing a > dict, already this program: http://paste.pocoo.org/show/575776/ raises > RuntimeError. You'll get slightly more obscure cases than changing a size > raise RuntimeError during iteration under PyPy. As far as I understood, if > you're mutating while iterating, you *can* get a runtime error. > > This does not even have a custom __eq__ or __hash__. Are you never iterating > over dicts? > > Cheers, > fijal -- --Guido van Rossum (python.org/~guido) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
