dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Thu, Feb 10, 2011 at 09:11:26AM +0000, Garth N. Wells wrote:
>
>
> On 10/02/11 09:09, Anders Logg wrote:
> > On Thu, Feb 10, 2011 at 08:48:55AM +0000, Garth N. Wells wrote:
> >>
> >>
> >> On 10/02/11 07:38, Johan Hake wrote:
> >>> On Wednesday February 9 2011 23:32:55 Anders Logg wrote:
> >>>> On Wed, Feb 09, 2011 at 04:40:19PM -0800, Johan Hake wrote:
> >>>>> Nice fix!
> >>>>>
> >>>>> I thought we needed to introduce shared_ptr versions of refinements call.
> >>>>> But I realise this fix only work for SWIG 2.0. As all shared_ptr_foo are
> >>>>> renamed to foo.
> >>>>>
> >>>>> We need to add an extra layer of %rename/%ignore for the SWIG 2.0 case.
> >>>>>
> >>>>> I can do this. But again it introduces another layer of complexity you
> >>>>> mention in your other post.
> >>>>
> >>>> That didn't seem to work. The buildbot now says:
> >>>>
> >>>> File
> >>>> "/home/fenicsslave/jhbuildbot/fenics/lib/python2.6/site-packages/dolfin/mes
> >>>> h/refine.py", line 30, in refine
> >>>>   return mesh.child_shared_ptr()
> >>>> TypeError: in method 'HierarchicalMesh_child_shared_ptr', argument 1
> >>>> of type 'dolfin::Hierarchical< dolfin::Mesh > *'
> >>>>
> >>>> What does that mean? mesh.child_shared_ptr() should return a
> >>>> shared_ptr to an object of class T (in this case Mesh), which it does
> >>>> in the C++ interface. It should not return a pointer to an object of
> >>>> class Hierarchical<T>.
> >>>
> >>> It is related to the "fix" Garth introduced. He used foo_shared_ptr, but that
> >>> one does not work for SWIG < 2.0. These methods are now ignored or renamed for
> >>> all SWIG versions, and everything should be well and fine for both versions of
> >>> SWIG.
> >>>
> >>
> >> I don't think that this is really a fix. The Python refine should return
> >> a shared_ptr, otherwise we can have problems with things going out of
> >> scope. The underlying problem is SWIG not wrapping the Mesh shared_ptrs
> >> properly.
> >
> > But isn't that exactly what's happening now? The C++ shared_ptr_foo()
> > functions are renamed to foo() so when you call foo() in Python you
> > get the shared_ptr.
> >
>
> That was my fix, which was reverted. Looks to me like a reference is
> returned.

>From site-packages/dolfin/mesh/refine.py:

  return mesh.child()

>From dolfin/swig/shared_ptr_classes.i:

   boost::shared_ptr<DERIVED_TYPE> child()
   { return self->child_shared_ptr(); }

So when mesh.child() is called in refine.py, it really returns
mesh.child_shared_ptr().


The point is that whenever we return something in a Python function
named foo(), we should always return a shared_ptr.

The Hierarchical/adaptive classes are probably (now) in better shape
than other parts of DOLFIN wrt correct use of shared_ptr.

--
Anders