On Jul 23, 2009, at 12:10 PM, Lisandro Dalcin wrote: > On Thu, Jul 23, 2009 at 10:29 AM, Richard > Clarke<rscla...@gmail.com> wrote: >> Thank you Robert, the explanation on how and where to use cdef was >> most helpful. I think it has just clicked(with a flag waving >> 'idiot'). >> >> The PyCObject concept is a nice idea, removing cdef foo_t *foo from >> outside of __init__ ? However, I see implications in memory >> deallocation. How does cython currently handle memory deallocation? > > I'm not sure you need PyCObject for your code ...
For sure PyCObject is not needed here. I was musing about a ptr <-> object conversion happening automatically via PyCObject, just as we handle the more basic numeric types. Deallocation of pointers needs to be handled by the user explicitly, so perhaps it's not a good idea to make this transparently easy. > >> >> I assume the best practice would be for users to deallocate memory in >> the class __del__ method (calling the appropriate wrapped c library >> destructor). > > Yes. More specifically, you should allocate stuff in __cinit__(), and > deallocate stuff in __dealloc__()... +1. To clarify, __cinit__ is called exactly once per object creation (no such guarantee with __init__). Likewise, __dealloc__ is always called exactly once upon collection. This makes memory management easy--essentially you're boostrapping of Python's refcounting. > > >> Otherwise does cython simply free(foo) or interprets the >> language to build a depth first deallocation method? > > Cython does not manage memory allocated with malloc()... you have to > manage deallocation yourself... > > >> I guess it >> should do the simplest free(foo), if the developer was lazy not to >> deallocate memory, they can suffer with memory leaks. I think I >> might >> have answered my own question here... >> > > In short, you have to modify your class, using something like this > > cdef class Bar: # NOTE: "cdef" class > > cdef foo_t *c_foo # NOTE: "cdef" instance (not class) member!!! > > def __cinit__(self): # NOTE: using "__cinit__", not "__init__" > self.c_foo = self.c_open() > > def __dealloc__(self): # NOTE: using "__dealloc__", not "__del__" > if self.c_foo != NULL: > free(self.c_foo) > > cdef foo_t* c_open(self): # NOTE: using "cdef", not "def", this > method will not show-up on Python side, it is a kind of internal, > private method. > cdef foo_t *foo = NULL > foo = init() > return foo > > > -- > Lisandro Dalcín > --------------- > Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC) > Instituto de Desarrollo Tecnológico para la Industria Química (INTEC) > Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) > PTLC - Güemes 3450, (3000) Santa Fe, Argentina > Tel/Fax: +54-(0)342-451.1594 > _______________________________________________ > Cython-dev mailing list > Cython-dev@codespeak.net > http://codespeak.net/mailman/listinfo/cython-dev _______________________________________________ Cython-dev mailing list Cython-dev@codespeak.net http://codespeak.net/mailman/listinfo/cython-dev
