OK, I still haven't run valgrind (still compiling the c++ library on
Linux) but I have used gdb to figure out more of what is going on.
This leads me to a more general question about __cinit__ and
__dealloc__:
I have 2 c++ class that one of which is a subclass of the other. I am
mirroring this hierarchy in cython by creating two cdef'd classes:
cdef class Foo:
cdef Foo_c *foo_ptr
def __dealloc__(self):
functionThatCallsDelete(self.foo_ptr)
cdef class Bar(Foo):
cdef Bar_c *bar_ptr
def __cinit__(self):
self.bar_ptr = newBar()
self.foo_ptr = <Foo_c *>self.bar_ptr
def __dealloc__(self):
functionThatCallsDelete(self.bar_ptr)
The nice thing about this approach is that all the methods on Foo,
also appear on Bar, but the pointer type is right. This (almost)
makes for a really nice way of having c++ subclasses reflected in
cython....
But, what I find is that the __dealloc__ method of both Bar and Foo
are being called. Because their underlying pointers (bar_ptr and
foo_ptr) point to the same thing, the second segfaults with a double
delete problem. So question:
How do people handle these things in cython? Can I prevent
__dealloc__ from being called twice?
Thanks
Brian
On Fri, Apr 18, 2008 at 3:00 PM, Michael.Abshoff
<[EMAIL PROTECTED]> wrote:
> Brian Granger wrote:
>
> Hi Brian,
>
>
> >> Yes, at least to see if it can spot the problem.
> >>
> >> To get started: Build your own python. Make sure to compile it with
> >> "--without-pymalloc" and also set the compile flags to "-O0 -g". Build
> >> valgrind 3.3.0 [or install it from binary packages] and run your code
> >> under it. If it segfaults valgrind [it happens to me somewhat regularly,
> >> but then usually something evil is happening in libSingular ;] go and
> >> check out the 3.4svn version.
> >
> > Thanks, I will try this out. I have never used valgrind, so this is
> > very helpful.
>
> Ok, to run it do
>
> valgrind --tool=memcheck --trace-children=yes --leak-resolution=high
> --log-file=foo ./path/to/python
>
> Then do your thing, quit python. At that point there should be foo.$PID
> in the cwd. For a C++ specific example where we did dumb things at
> dealloc time from Sage look at
>
> http://trac.sagemath.org/sage_trac/ticket/1573
>
> Also: searching for delete[] in Sage's trac will turn up a number of
> other examples. If you get stuck feel free to post the example here and
> once I take a look at the code I may be able to help you out.
>
>
> >> Let me know if you have any trouble.
> >
> > Thanks
> >
> > Brian
> >
>
> In the end I would assume people won't mind if some easy cases would get
> added to the Cython wiki in form of a tutorial, i.e. if you do FOO it
> blows up but BAR fixes it. I have meant to do this for a long, long time
> in the Sage wiki, but never got around to it. But it should probably be
> in the Cython wiki for obvious reasons.
>
> Thought?
>
>
>
> Cheers,
>
> Michael
> _______________________________________________
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>
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