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

[Warner Losh]

On Thu, Sep 8, 2022 at 4:26 PM Warner Losh <imp at bsdimp.com> wrote:

>
>
> 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 should have added it was one of the 23 files in 4.4lite that was
acknowledged
as having some AT&T code that AT&T agreed to release...


> 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
>
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