Re: Memory leaks and user data

[Javier Guerra Giraldez <javier@...>]

Fabien wrote:
> Hi,
>
> I have a memory leak problem: some userdata objects are never GC'd, and 
> I really fail to find where it's referenced. Is there a well-known 
> recipe to help tracking down such leaks, if I know which userdata I'm 
> chasing?
one common issue with userdata is that it's hard to make the lua GC 
account for it's full weight.
the worst (and still very common) case is when you use a third party 
library to alloc a complex and heavy object, and create a userdata to 
hold just the pointer.  The Lua CG will count only 4 bytes, unaware of 
the big memory hog.  you can find yourself with thousands of these 
objects, and the CG doesn't bother to delete them.
the usual solution is to add a 'close' method to the userdata, and 
remember to close any object you don't need anymore.
of course, there's always the "but the CG _should_ do this for me!" 
argument; but think about open files, or DB connections... it's obvious 
they should be closed ASAP, CG or not.  just the same with any 
resource-hogging library.
--
Javier