2011/4/20 Stefan Behnel <stefan...@behnel.de>: > Vitja Makarov, 20.04.2011 10:26: >> >> 2011/4/18 Stefan Behnel: >>> >>> Vitja Makarov, 18.04.2011 06:38: >>>> >>>> 2011/4/18 Stefan Behnel: >>>>> >>>>> Vitja Makarov, 17.04.2011 17:57: >>>>>> >>>>>> 3. check_yield_in_exception() >>>>> >>>>> I added this because I found a failing pyregr test that uses it >>>>> (testing >>>>> the >>>>> @contextmanager decorator). >>>>> >>>>> >>>>>> Cython calls __Pyx_ExceptionReset when except block is done, so when >>>>>> yield is there no exception reset is called. >>>>>> >>>>>> I'm not sure how to fix this. >>>>> >>>>> I'm not completely sure either. >>>>> >>>>> >>>>>> import sys >>>>>> >>>>>> def foo(): >>>>>> """ >>>>>> >>> list(foo()) >>>>>> [<type 'exceptions.ValueError'>, None] >>>>>> """ >>>>>> try: >>>>>> raise ValueError >>>>>> except ValueError: >>>>>> yield sys.exc_info()[0] >>>>>> yield sys.exc_info()[0] # exc_info is lost here >>>>> >>>>> I think (!), the difference here is that CPython actually keeps the >>>>> exception in the generator frame. We don't have a frame, so we have to >>>>> emulate it using the closure class. I guess we'll have to store away >>>>> the >>>>> exception into the closure when we yield while an exception is being >>>>> handled, and restore it afterwards. Note: this is not the exception >>>>> that >>>>> is >>>>> freshly *being* raised (the "_cur*" fields in the thread state), it's >>>>> the >>>>> exception that *was* raised and is now being handled, i.e. the thread >>>>> state >>>>> fields without the "_cur", that are reflected by sys.exc_info(). >>>> >>>> Interesting difference between py2 and py3: >>>> >>>> def foo(): >>>> try: >>>> raise ValueError >>>> except ValueError: >>>> yield >>>> raise >>>> list(foo()) >>>> >>>> File "xxx.py", line 7, in<module> >>>> list(foo()) >>>> File "xxx.py", line 6, in foo >>>> raise >>>> TypeError: exceptions must be old-style classes or derived from >>>> BaseException, not NoneType >>>> >>>> It seems that exception info is completely lost (tried 2.6, 2.7) and >>>> seems to be fixed in python3. >>> >>> Not surprising. The implementation is completely different in Py2 and >>> Py3, >>> both in CPython and in Cython. It's actually much simpler in Cython under >>> Py3, due to better semantics and C-API support. That also implies that >>> there's much less Cython can do wrong in that environment. ;-) >>> >>> >>>> Btw exception info temps are already saved and restored between yields. >>> >>> Right, but the exc_info itself is not reset and recovered around the >>> yield. >>> As I said above, generators have their own lifetime frame in CPython, and >>> exceptions don't leak from that. So, whenever it's the generator (or code >>> called by it) that raises an exception, that must be kept local to the >>> generator. >> >> Please review: >> >> https://github.com/vitek/cython/commit/73014aaed10b82a3f632d7f86212f86280c55858 >> >> I've added __Pyx_Generator_SwapExceptions() method and call it right >> before resume switch and before return from yield. It swaps generator >> exception state with thread local. > > Looks good to me. I assume this fixes the problem? Then please push it into > mainline. >
old pull request is still there ;) https://github.com/cython/cython/pull/25 Does __Pyx_ExceptionReset() steal references to args, so they should not be decrefed later? -- vitja. _______________________________________________ cython-devel mailing list cython-devel@python.org http://mail.python.org/mailman/listinfo/cython-devel
