CPython and a C extension using Boehm GC

[MrJean1]

FWIIW, I built GC 6.7 on a RHEL 3 (Opteron) system using

  ./configure --prefix=... --enable-redirect-malloc --enable-
threads=posix --enable-thread-local-alloc
  make; make check; make install

Then, I tried running a few examples with 3 different, existing Python
binaries each pre-loaded with the libgc.so library

  env  LD_PRELOAD=.../libgc.so  <python> ....

One is Python 2.2.3 included in RHEL 3, one is a Python 2.5.1 build
and is a Python 3.0a2 build, all 64-bit.  All seemed to work OK.

These are 3 existing Python binaries without any call to GC_INIT().
AFAICT, on Linux, GC_INIT is a no-op anyway.

/Jean Brouwers


On Dec 26, 7:14 am, MrJean1 <MrJe... at gmail.com> wrote:
> It depends on how the GC inside the extension is built.  If it is a
> drop-in replacement for malloc, then GC *must* be loaded and
> initialized upfront if possible.  There is no need to memcpy anything
> between Python and the extension.
>
> However, if GC does not replace malloc, etc., then GC-ed memory is
> only used within the extension.  GC_INIT can be called when the
> extension is loaded and memcpy-ing between Python and the extension is
> mandatory.
>
> There are other details to consider.  For example, on some platforms,
> GC *must* be initialized from the main executable.  That may preclude
> both scenarios, altogether.
>
> /Jean Brouwers
>
> On Dec 25, 7:35 pm, Andrew MacIntyre <andy... at bullseye.apana.org.au>
> wrote:
>
> > malkarouri wrote:
> > > Is it possible to write a Python extension that uses the Boehm garbage
> > > collector?
> > > I have a C library written that makes use ofboehm-gcfor memory
> > > management. To use that, I have to call GC_INIT() at the start of the
> > > program that uses the library. Now I want to encapsulate the library
> > > as a CPython extension. The question is really is that possible? And
> > > will there be conflicts between theboehm-gcand Python memory
> > > management? And when should I call GC_INIT?
>
> > It probably should be possible with some caveats:
> > - memory allocated by Python is never passed into the library such that
> >    it also ends up being subject toboehm-gc;
> > - memory allocated by the library is never used by Python objects.
>
> > So memcpy()ing between library allocated and Python allocated memory
> > would seem to be a way to achieve this.
>
> > I would call GC_INIT in the extension's import routine
> > (init<module_name>()) for a C extension, and immediately after loading
> > the library if using ctypes.
>
> > --
> > -------------------------------------------------------------------------
> > Andrew I MacIntyre                     "These thoughts are mine alone..."
> > E-mail: andy... at bullseye.apana.org.au  (pref) | Snail: PO Box 370
> >         andy... at pcug.org.au             (alt) |        Belconnen ACT 2616
> > Web:    http://www.andymac.org/             |        Australia