[Python-Dev] Let's stop eating exceptions in dict lookup (original) (raw)

Armin Rigo arigo at tunes.org
Mon May 29 19:11:48 CEST 2006

Hi all,

I've finally come around to writing a patch that stops dict lookup from eating all exceptions that occur during lookup, like rare bugs in user eq() methods. After another 2-hours long debugging session that turned out to be caused by that, I had a lot of motivation.

http://python.org/sf/1497053

The patch doesn't change the PyDict_GetItem() interface, which is the historical core of the problem. It works around this issue by just moving the exception-eating bit there instead of in lookdict(), so it gets away with changing only dictobject.c (plus ceval.c's direct usage of ma_lookup for LOAD_GLOBAL). The benefit of this patch is that all other ways to work with dicts now correctly propagate exceptions, and this includes all the direct manipulation from Python code (including 'x=d[key]').

The reason I bring this up here is that I'm going to check it in 2.5, unless someone seriously objects. About the objection "we need a better fix, PyDict_GetItem() should really be fixed and all its usages changed": this would be good, and also require some careful compatibility considerations, and quite some work in total; it would also give a patch which is basically a superset of mine, so I don't think I'm going in the wrong direction there.

A bientot,

Armin

More information about the Python-Dev mailing list