[TUHS] Re-implementations/Clean-Rooms et al.

[Warner Losh]

On Thu, Sep 8, 2022 at 4:16 PM Larry McVoy <lm at mcvoy.com> wrote:

> On Thu, Sep 08, 2022 at 05:50:37PM -0400, Clem Cole wrote:
> > > BSD is a different beast, as they were literally replacing the AT&T
> source
> > > code before their eyes, so there isn't much argument that can be made
> for
> > > 4.4BSD being a "clean-room" implementation of UNIX.
> >
> > It was not a clean-room as Arthur defined it.   It was rewritten over
> time,
> > which replaced AT&T's implementation.  Which is all that was ever
> claimed.
>
> And it's a false claim.  Go look at the Bell Labs bmap() and the BSD
> bmap(), the last time I looked they were bit for bit identical.
>

Yea, this was part of the de minimis copying that was acknowledged...
It was mostly rewritten with most of AT&T's code gone. It's 110 lines of
code,
out of ~18,000 lines of kernel code. And the structure in 4.4BSD is somewhat
different with balloc() being completely different than the rest of V7's
subr.c.


> I looked there because I split bmap() into bmap_read() and bmap_write()
> because the read path is trivial and the write path is quite a bit more
> difficult (this was all for the work srk imagined, and I did, to get
> rid of the rotational delays).  So I was pretty familiar with that
> code path and as of about 20 years ago, well past 4.4BSD, bmap() was
> unchanged from either v7 or 32v.
>

But it likely didn't matter, since 32v likely lost its copyright protection
due
to AT&T distributing too many copies without the required copyright
markings.
At least that was the preliminary ruling that caused the suit to be
settled...
AT&T didn't want it finalized, though the cat was somewhat out of the bag
at this point...


> The weird thing is it isn't that hard to write something that would
> walk the code and find other examples.  Nobody seemed to care.
>

Yea, most of the rest of the code around it was rewritten, but not that.

Warner
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://minnie.tuhs.org/pipermail/tuhs/attachments/20220908/7902a1ca/attachment.htm>