Re: GUILE GC -- Write barrier for vectors

[Han-Wen]

address@hidden writes:
> On Tue, 16 Jul 2002, Han-Wen wrote:
> 
> > I don't know. Some form of the idea seems to be patented, but I can't
> > access the text of the patent, so I'm not sure (it's no. 251554).
> > (and even if I could -- you never know: the only person qualified to
> > judge wether a patent is applicable are IP lawyers and IP judges. With
> > those millions and millions of patents it is unlikely that none of
> > them are covering GUILE as it is).
> 
> Maybe it would make sense to ask the FSF about the issue:  If the patent
> is not actually claimed or if there is an agreement to allow its use in
> free software, there wouldn't be any restrictions at all.  Probably Marius
> will know about how to contact the FSF legal department to get an official
> statement about it.

(short reply, I'm busy with something else right now.)

I talked to Michael Livshin, who says to have quit GUILE development.

He notes that CMU CL and its derivative SBCL have been using a mostly
copying gen GC for 6 years now. Squish (a C++ library) also uses
it. Compaq is not actively enforcing this patent, so it seems. (And
"only" 5 years until it is no longer valid)

> Wouldn't the compiler move the code out anyway?  (I don't know how
> complicated the flagging code would look like, so it may be that this is
> impossible...)

It depends on what code is in the loop. But I guess you're right. The
cases where it is surely safe to move the flagging, are also the ones
that a compiler could optimize.

-- 

Han-Wen Nienhuys   |   address@hidden   |   http://www.cs.uu.nl/~hanwen