Debugging memory leak.

[David Brown]

On Mon, Oct 08, 2007 at 10:23:17PM -0700, David Brown wrote:

> I seem to have something else in my program that is making lots of stray
> pointers for the GC to follow.  My program consistently leaks memory until
> it is killed by running out of address space (or I kill it because it is
> trying to swap my machine to death).

I think I found my problem.  I have something like this:

   class Foo {
     ubyte[20] hash;
     ...
   }

and a _lot_ of these are alive at any given time.  The hash is a sha1 hash,
and so tends to be evenly distributed.

It appears that heap objects only have a single flag indicating whether or
not they have pointers, and since classes do have pointers, the GC will
look at the "pointers" in the hash to see if they hit anything.  Build up a
reasonable set of these and something will point to almost everything.

It's going to take me a little while to change the code to not do this (it
isn't quite as simple as my example).  I was concerned about having 20
bytes living in its own gc allocation being wasteful, but leaking nearly
everything is much more wasteful :-)

Dave