Re: FYI: Linker & Verifier fixes (really GC mark procedures)

[Hans Boehm <Hans.Boehm@hp.com>]

On Thu, 2 Feb 2006, Tom Tromey wrote:

> >>>>> "Tom" == Tom Tromey <tromey@redhat.com> writes:
>
> Tom> I did a little work on the gcjx branch in this area.  But it has
> Tom> never been tested.  Anyway the idea was that the compiler could emit
> Tom> real mark descriptors for Class, by special-casing it a bit in
> Tom> boehm.c.
>
> I looked at this today.  We can't scan Class using a bitmap descriptor
> yet, because its layout is wrong for this.  The descriptor overflows
> and we have to fall back to procedural scanning.
>
Just to be clear, since I'm not quite sure I understand what you're saying
here:  I don't think it's the mark procedure per se
that's the problem.  The issue is having a mark procedure that
walks complicated data structures and traces those instead of just
pushing directly referenced objects.

In particular, I don't think there's a problem with using a mark
procedure to deal with bitmap overflow issues, as we do for a few
ordinary objects.  It does normally add some overhead.  But if the
object is large enough to overflow (especially a 64-bit) bitmap, that's
probably not dominant.

Hans