Elizabeth Mattijsen said: > With mixed succes, and with (currently) serious memory leaks. This was > recently discussed on the Perl XML list. Basic problem is that Perl > destruction of SV's is causing parts of the libxml/libxslt > allocated memory to be freed when it shouldn't yet.
i just spent quite a bit of time working on a solution to exactly this problem. the C object i was wrapping was reference-counted[1], and the perl wrapper took a reference on the object. thing is, i needed the perl object to stick around as long as the C object, and there were cases when the C object could still be alive in the library without the perl wrapper. the trick (not supplied by me, but by marc lehmann, who knows the black art much better than i do) was to treat the perl object and the C object as a unit, and "trade" refcounts between them. this resulted in the slightly bizarre situation that DESTROY can be called more than once on a perl object if the C object is being kept alive by other code. incidentally, a beautiful part of the solution was keeping the pointer to the C object in magic associated with the perl object, invisible and thus unbreakable from prying perl fingers. if your C object isn't refcounted, this may prove difficult for you. for a non-refcounted structure[2], my solution was to provide a two-layer wrapper. the perl object is an SvRV->SvIV->C wrapper structure->actual object of interest. the C wrapper structure is a throwaway struct which contains useful information like the type of the pointed-to-object, and whether or not the pointed-to-object should be destroyed with the wrapper. there are lots of other tricks, but they all are specific to how you actually will wind up using the structures you're wrapping and how those structures behave. what i've told you may be useless directly, but the concepts may be applicable indirectly. hope that's mildly helpful. *grin* [1] GObject: http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/gtk2-perl/gtk2-perl-xs/Glib/GObject.xs?annotate=1.9 [2] GBoxed: http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/gtk2-perl/gtk2-perl-xs/Glib/GBoxed.xs?annotate=1.4 -- muppet <scott at asofyet dot org>
