Dear Stefan,
I've created a pull request:
https://github.com/boostorg/python/pull/64
Cheers,
Willi.
> Hi Willi,
>
> On 26.04.2016 16:19, Wilfried Karel wrote:
>> Dear list,
>>
>> I suggest to insert an assertion before calling Py_DECREF/Py_XDECREF
>> which ensures that the reference count before the call is larger than
>> zero. Otherwise, this means that a PyObject that has already been
>> destroyed is planned to be destroyed a second time - which will not
>> happen, as the reference count is of unsigned integer type, and so it
>> will become a very large number - but it keeps a PyObject alive that
>> references destroyed memory.
>>
>> I suggest to insert such assertions, because this easily detectable
>> programming error is hard to track based on a possibly resulting
>> segmentation fault at some later point during program execution (as has
>> happened to me). Maybe this would be detected by a debug-build of
>> Python, but in my environment, it would be troublesome to link it,
>> together with providing possibly needed debug-builds of other Python
>> extension packages (e.g. NumPy).
>>
>> Thus, I suggest to insert
>> assert( Py_REFCNT(m_ptr) > 0 );
>>
>> at the beginning of
>> api::object_base::~object_base()
>> and
>> void decref(T* p)
>>
>> and to insert
>> assert( p == nullptr || Py_REFCNT(python::upcast<PyObject>(p)) > 0 );
>> at the beginning of
>> void xdecref(T* p)
>
> I'm curious: how do you manage to get non-garbage-collected objects with
> zero ref-counts ?
>
> If you can reproduce such cases I think your suggestion is indeed a good
> idea. In that case, would you mind submitting a patch / PR (against the
> 'devel' branch) ? (And seeing you using 'nullptr' above reminds me:
> please make sure the code is backward compatible with pre-C++-11).
> Please include a test case to demonstrate the failing and fixed behavior.
>
>> Cheers,
>> Willi.
>
> Many thanks !
>
> Stefan
>
> --
>
> ...ich hab' noch einen Koffer in Berlin...
--
_____ _____ _____ Technische Universität Wien
DI Wilfried Karel /____// ___// / Dept. of Geodesy & Geoinform.
wilfried.karel@ // __ / /__ / // / Research Groups Photogrammetry
geo.tuwien.ac.at //__/// /__ / // / & Remote Sensing
+43 1 58801 12244 /____//____//____/ Gusshausstr. 27-29, A-1040 Wien
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