Every time I need to resolve a leaked scalar problem, I spend hours trying to guess where could it possibly come from. Now add to that problem the fun of randomness, where sometimes the leaked scalar is happening every 10th run or so, so it's litterally improssible to debug this.
I feel your pain. When I was developing the version objects in the core, I had a persistent leak when I did something particular (the details of which escape me now). And yes, the bugger of it was that by the time Perl noticed that this scalar is going to leak, it has already deallocated pretty much everything from the scalar except the reference count, so there was nothing to examine.
I did have some luck, I recall, when I would notice that the same memory address was the same. I would manually insert an sv_dump() in the Perl source code, hoping to catch whatever it was that was allocating this thing. Unfortunately in my case, the scalar usually contained an RV, so I would still have no idea what was going on. It would be vastly useful to extend the C-level dumping code to have an sv_rdump which would be a recursive dump (ala Devel::Peek) which could reveal what was really contained in that scalar. This would be incredibly useful to examine hashes and arrays, too, at the C-level.
It's still not going to be easy to track these little buggers down, because by the time Perl can tell that a scalar is going to leak, it has already leaked (i.e. the information contained within the scalar is mostly gone). Perhaps a new Perl level sub within Devel::Peek could be added which would take a memory address and dump the contents. You could add this line to an END block and see if you can catch the scalar /in situ/ before anything has been actually deallocated. Of course, the act of adding that code will disturb the memory allocation, so there might be a couple of iterations before you figure out what the correct memory address is to dump the leaker.
John
-- John Peacock Director of Information Research and Technology Rowman & Littlefield Publishing Group 4720 Boston Way Lanham, MD 20706 301-459-3366 x.5010 fax 301-429-5747
