[pypy-dev] Mysterious IndexError in service running with PyPy

[hubo]

Thank you for your explaination!

One more thing I would like to confirm: looks like in PyPy3, a "yield from my_generator()" expression delegates all exceptions inside, so the finalizer in my_generator() is always executed. Am I right?

2018-05-22 

hubo 



发件人：Armin Rigo <armin.rigo at gmail.com>
发送时间：2018-05-22 14:21
主题：Re: [pypy-dev] Mysterious IndexError in service running with PyPy
收件人："hubo"<hubo at jiedaibao.com>
抄送："William ML Leslie"<william.leslie.ttg at gmail.com>,"PyPy Developer Mailing List"<pypy-dev at python.org>

Hi, 

On 22 May 2018 at 04:46, hubo <hubo at jiedaibao.com> wrote: 
> I think I found the cause, happily it is not a PyPy bug (although it is 
> PyPy-related). Some generators are calling some cleanup code in the 
> "finally" clause, but they are not correctly collected in PyPy until GC 
> (because PyPy does not use reference counting). Apparently when they are 
> collected by GC module, the "finally" clause is executed in a separated 
> thread. 

Unlike Java, we're not purposefully running finalizers in its own 
threads: instead, if your program has got more than one thread 
running, finalizers will run in the one where the GC happens to run. 
There isn't much we can do about that. 

All these hard GC issues also exist on CPython, but they are just more 
hidden.  Typically, if there is a cycle of objects which itself holds, 
indirectly, a reference to the generator-iterator, then you get the 
same effect: the cycle will be broken by the GC module of CPython at a 
random point in time and from a random thread, too.  So we can argue 
that you potentially have a bug even on CPython, in the sense that an 
apparently unrelated change somewhere else can make the same bug 
appear on CPython. 


A bientôt, 

Armin. 
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