On Wed, Mar 21, 2012 at 1:03 AM, Stefan Behnel <stefan...@behnel.de> wrote: > Hi, > > I was made aware of a difference between the ways Cython and CPython raise > exceptions. In CPython, the exception is always instantiated immediately, > even if you raise a plain type, i.e. > > raise TypeError > > will actually raise a TypeError() instance. In Cython, the exception is > only stored, not instantiated. The difference can show when the > instantiation fails for some reason or has other side effects. Depending on > *when* and *if* the exception is actually instantiated, these effects may > show at unexpected times during execution, or may be not occur at all in > some corner cases (e.g. when the exception is shadowed by another one in > Py2 or caught by an except block in Cython that contains only C code). > > I think this should change. We may consider leaving it as it is for known > exception types that are created without arguments, but otherwise, and > especially for user provided exceptions, we should take the safer route of > always instantiating them, like CPython does. That implies a certain > performance hit in some rather rare cases (of which an explicitly raised > StopIteration is the most visible one, if not exempted), but under normal > conditions where an exception is regularly caught at some point, the > overhead is the same and it would have less surprising corner cases.
+1. One could consider making an exception for the no-argument builtin (side-effect-free) ones, but this would just be an optimization, and we're typically already in an expensive, exceptional state at this point. - Robert _______________________________________________ cython-devel mailing list cython-devel@python.org http://mail.python.org/mailman/listinfo/cython-devel
