ffc team mailing list archive

["Garth N. Wells" <gnw20@xxxxxxxxx>]

Anders Logg wrote:
> On Mon, Nov 24, 2008 at 10:15:48PM +0100, Johan Hake wrote:
> > On Monday 24 November 2008 22:02:43 Anders Logg wrote:
> > > On Mon, Nov 24, 2008 at 09:39:45PM +0100, Johan Hake wrote:
> > > > Hello!
> > > >
> > > > While working on the python interface of dolfin I come over a memory
> > > > corruption in the dolfin::Form destructor. While ffc -ldolfin produce
> > > > code to instantiate a dolfin::Form it does not take care of deleting the
> > > > ufc_form.
> > > >
> > > > In the destrutor of the base class Form there is a
> > > >
> > > >   delete _ufc_form;
> > > >
> > > > I do not know if this while prevent any memory leak from the ffc produced
> > > > code, e.g., if the base class destructor is not calle or something, but
> > > > that line _will_ corrupt any try to instantiate a dolfin::Form directly
> > > > using an ufc_form, which we have to do in PyDOLFIN.
> > > >
> > > > My suggestion is to remove the above mentioned line from dolfin::~Form(),
> > > > which I have done locally, and add the same line in the destructor of the
> > > > derived class produced by ffc.
> > > >
> > > > Any comment?
> > > >
> > > > Johan
> > > Sounds good. Patches welcome. Will get started on applying your other
> > > patches.
> > Well, I am not so into the code generation part of ffc, so I would have hoped 
> > you could have a look at it ;)
>
> Sure, it's an easy fix (in dolfinformat.py). I will fix it as soon as
> I get a chance.
>
> > Btw, why isn't _ufc_form stored as a shared_ptr? It would make it a bit 
> > easier. 
>
> It wasn't needed at the time. I'll think about making it a shared
> pointer.

Making it a shared_ptr would be the best option. dolfin::Form should 
have a constructor that accepts a shared_ptr to a ufc::form. My problem 
with delete in the generated code and removing it from Form is that a 
pointer to a ufc::form appears in Form, but no matching delete. We 
shouldn't rely on the derived class to clean up the base class.

Garth

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