dolfin team mailing list archive

[Johan Hake <hake.dev@xxxxxxxxx>]

I just pushed an implementation of where MeshDomain keep a reference to
the mesh, similar to MeshData. It is perfectly possible to make this
blow up similare to the MeshData example below in Python.

However, if the user destroys the mesh and then tries to use an objects
which is clearly associated with that mesh things are bound to go bad.

Johan

On 02/11/2013 01:19 PM, Johan Hake wrote:
> On 02/11/2013 01:09 PM, Martin Sandve Alnæs wrote:
>> Because of the circular depencency and reference counts not becoming
>> zero? It could be a weak pointer:
>> http://www.boost.org/doc/libs/1_53_0/libs/smart_ptr/weak_ptr.htm
> 
> To use weak pointers one need the shared_ptr first, right? Because
> MeshDomains are created withing the constructor of Mesh you do not have
> that.
> 
> A way to "solve" this is to just store a reference to the mesh, similar
> to what is done in MeshData. This is of course not bullet proof as one
> easily can make it blow up by:
> 
> from dolfin import *
> m = UnitSquareMesh(2,2)
> md = m.data()
> del m
> md.create_mesh_function("boom", 0)
> 
> Any nice fixes for this situation you C++ guros out there?
> 
> Johan
> 
> 
>> Martin
>>
>>
>> On 11 February 2013 13:02, Anders Logg <logg@xxxxxxxxx
>> <mailto:logg@xxxxxxxxx>> wrote:
>>
>>     On Mon, Feb 11, 2013 at 09:00:20AM +0100, Johan Hake wrote:
>>     > I am adding some functionality to MeshDomains, (actually to SubMesh,
>>     > which soon also propagates MeshDomains to the new mesh), and wonder if
>>     > there where any good reasons why a MeshDomain does not have a
>>     pointer to
>>     > the parent mesh?
>>     > If such was provided during construction we could skip the
>>     annoying mesh
>>     > argument in:
>>     >  facets_domains = mesh.domains().facet_domains(mesh)
>>
>>     Feel free to add it if it is useful. At the time of implementation, I
>>     wanted to avoid a pointer to the parent to keep the number of pointers
>>     floating around at a minimum (especially in this case since it can't
>>     be a shared pointer).
>>
>>     --
>>     Anders
>>
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>