Re: Fix for segfault in plpython's exception handling

Thank you! Glad to see that the report was useful.

On Fri, Dec 9, 2016 at 9:33 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> I wrote:
> > Rafa de la Torre <rtorre(at)carto(dot)com> writes:
> >> exc = PyErr_NewException(exception_map[i].name, base,
> dict);
> >> + Py_INCREF(exc);
> >> PyModule_AddObject(mod, exception_map[i].classname, exc);
>
> > Hm. Seems like if this is a problem, the code for the other three
> > exceptions is being a bit careless: it does do Py_INCREFs on them,
> > but not soon enough to ensure no problems. Also, I wonder why that
> > code checks for a null result from PyErr_NewException but this doesn't.
>
> > Good catch though. A naive person would have assumed that
> > PyModule_AddObject would increment the object's refcount, but
> > the Python docs say "This steals a reference to value", which
> > I guess must mean that the caller is required to do it.
>
> For me (testing with Python 2.6.6 on RHEL6), this test case didn't result
> in a server crash, but in the wrong exception object name being reported.
> Tracing through it showed that a python GC was happening during the loop
> adding all the exceptions to the spiexceptions module, so that some of the
> exception objects went away and then were immediately reallocated as other
> exception objects. The explicit gc call in the test case wasn't
> necessary, because the problem happened before that. Fun fun.
>
> I've pushed a patch that deals with all these problems. Thanks for
> the report!
>
> regards, tom lane
>

--
Rafa de la Torre
rtorre(at)carto(dot)com