On Wed, Apr 26, 2017 at 10:38 PM, Cem Karan <cfkar...@gmail.com> wrote:
> > On Apr 24, 2017, at 8:54 PM, Jon Ribbens <jon+use...@unequivocal.eu> > wrote: > > > On 2017-04-24, CFK <cfkar...@gmail.com> wrote: > >> Long version: I'm trying to write bindings for python via ctypes to > control > >> a library written in C that uses the bdwgc garbage collector ( > >> http://www.hboehm.info/gc/). The bindings mostly work, except for when > >> either bdwgc or python's garbage collector decide to get into an > argument > >> over what is garbage and what isn't, in which case I get a segfault > because > >> one or the other collector has already reaped the memory. > > > > Make your Python C objects contain a pointer to a > > GC_MALLOC_UNCOLLECTABLE block that contains a pointer to the > > bwdgc object it's an interface to? And GC_FREE it in tp_dealloc? > > Then bwdgc won't free any C memory that Python is referencing. > > OK, I realized today that there was a miscommunication somewhere. My > python code is all pure python, and the library is pure C, and it is not > designed to be called by python (it's intended to be language neutral, so > if someone wants to call it from a different language, they can). That > means that tp_dealloc (which is part of the python C API) is probably not > going to work. > > I got interrupted (again) so I didn't have a chance to try the next trick > and register the ctypes objects as roots from which to scan in bdwgc, but > I'm hoping that roots aren't removed. If that works, I'll post it to the > list. > > Thanks, > Cem Karan Right, apparently I win at the 'late reply' game. That said, I wanted to give Jon Ribbens credit for his idea, because it was very close to what I used in the end. The only difference is that I also used weakref.finalize() to tie a finalizer to the lifetime of the ctypes pointer that I was using. The finalizer called GC_FREE() to free the uncollectable block, which allowed the C allocator to cleanup memory. The only thing I never figured out was how to get a C block to hold onto python memory. I didn't need it, but it felt like it would make for a nice duality with the method above. Thanks, Cem Karan -- https://mail.python.org/mailman/listinfo/python-list
