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April 2020

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missing `UCHAR` in `ctypes.wintypes`?
by Kingsley McDonald 08 Apr '20

08 Apr '20

hello :) i'm writing a small library

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Re: [Python-Dev] Problem with instantiating a C extension class from another class
by Nick Coghlan 05 Apr '20

05 Apr '20

Hi Musbur, While python-dev is specifically for core development, the "specific interest group" mailing lists are for both change proposals and existing usage questions. I've cc'ed capi-sig on this reply. Cheers, Nick. On Sat., 4 Apr. 2020, 2:02 am Musbur, <musbur(a)posteo.org> wrote: > Hello, > > (I've asked this question before on python-list but only got scarce > and ultimately unhelpful answers. Although this isn't about Python > development itself, I'm assuming that there is more CPython > knowledge on this list than on the other, so please bear with me.) > > I've written a C extension module, each defining a class > (called Series and CLHist, respectively). I can import both modules in > Python and use the classes. Everything works fine, also according to > valgrind. > > Now I want to return a Series instance directly from a CLHist > method, and that immediately crashes Python with a segfault. > > Here's a bit of code and just the _new, _init, and _finalize methods > which I've sprinkled with debugging code. When I instantiate a Series > object from Python, I see output from all three methods. When I call > pyseries_new() from C, none of the three functions are called and it > crashes. > > At some point I thought maybe I should call PyType_Ready() from the C > side before instantiating Series. In a "standard" (system) Python > installation, it printed the desired debugging output and crashed > later. Under a debugging Python installation I built it outputs > nothing except an interesting post-mortem "Fatal Python error: UNREF > invalid object" (see below). > > Here's my C code with the boilerplate stuff left out. > > typedef struct { > PyObject_HEAD > struct clh_series *series; > } Series; > > static PyObject *Series_new(PyTypeObject *type, > PyObject *args, PyObject *kw) { > Series *self; > > self = (Series *) type->tp_alloc(type, 0); > fprintf(stderr, "Series_new(%p)\n", self); > self->series = NULL; > return (PyObject*)self; > } > > static int Series_init(Series *self, PyObject *args, PyObject *kw) { > fprintf(stderr, "Series_init(%p)\n", self); > self->series = NULL; > return 0; > } > > static void Series_finalize(PyObject *self) { > fprintf(stderr, "Series_finalize(%p)\n", self); > clh_series_free(((Series*)self)->series); > } > > /* To create a new Series object directly from C */ > PyObject *pyseries_new(struct clh_series *series) { > Series *pyseries; > > pyseries = PyObject_New(Series, &series_type); > PyObject_Init((PyObject *)pyseries, &series_type); > pyseries->series = series; > return (PyObject *) pyseries; > } > > Here's the debugging output: > > * ob > object : <refcnt 0 at 0x7f1a4e2f97a8> > type : tuple > refcount: 0 > address : 0x7f1a4e2f97a8 > * op->_ob_prev->_ob_next > object : <_Series object at 0x7f1a4e2ee9d0> > type : _Series > refcount: 1 > address : 0x7f1a4e2ee9d0 > * op->_ob_next->_ob_prev > object : <refcnt 0 at 0x7f1a4e2f97a8> > type : tuple > refcount: 0 > address : 0x7f1a4e2f97a8 > Fatal Python error: UNREF invalid object > _______________________________________________ > Python-Dev mailing list -- python-dev(a)python.org > To unsubscribe send an email to python-dev-leave(a)python.org > https://mail.python.org/mailman3/lists/python-dev.python.org/ > Message archived at > https://mail.python.org/archives/list/python-dev@python.org/message/ILMRMQ6… > Code of Conduct: http://python.org/psf/codeofconduct/ >

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