RL02 version of UNIX6?

Guy Sotomayor Jr ggs at shiresoft.com
Thu Feb 2 11:58:37 CST 2017

> On Feb 2, 2017, at 9:25 AM, Bill Gunshannon <bill.gunshannon at hotmail.com> wrote:
> From: cctalk [cctalk-bounces at classiccmp.org] on behalf of Paul Koning [paulkoning at comcast.net]
> Sent: Thursday, February 2, 2017 9:34 AM
> To: General Discussion: On-Topic and Off-Topic Posts
> Cc: jnc at mercury.lcs.mit.edu
> Subject: Re: RL02 version of UNIX6?
>> On Feb 1, 2017, at 9:30 PM, Noel Chiappa <jnc at mercury.lcs.mit.edu> wrote:
>>> From: Paul Koning
>>> Yes, GCC should do that correctly. ... Dealing with the output might be
>>> a nuisance ... You may need some post-processing to cast the output
>>> into the syntax that V6 "as" expects.
>> Actually, dealing with the _input_ is going to be a PITA (so my suggestion
>> was, in retrospect, not really a plausible one). The problem is that V6 is
>> written in an early dialect of C, one which I am sure would cause GCC would
>> toss its cookies, if fed to it.
>> Some things, like "a =+ b;" would be easy to fix; likewise "int a 1;" instead
>> of "int a = 1;". But the Unix kernel is shot through with places where are
>> int is used as a structure pointer, etc, without benefit of a cast (casts
>> weren't invented until later). And a lot of stuff like that.
> Yes, that would be an interesting issue.  One answer would be to write a new front end ("Old C").  That's probably more work than can easily be justified, though.
> __________________________________________________________________
> What version of GCC is being used here? I thought they removed support
> for the PDP-11 more than a deacde ago.
> And, while I am at it, based on what people are saying here I assume they also
> removed the switch for K&R mode.

It’s not just K&R mode.  It’s v6 mode.  C had some deficiencies prior to the release
of v7.  The most notable was that <larg> <op=> <expression> (e.g. a += 1) was in
v6 actually <larg><=op><expression> (e.g a =+ 1).  This led to ambiguities:
if you have a=+1 do you mean to increment a by 1 or assign +1 to a?  I don’t recall
if v7 cc was transitory (in that it allowed both forms) but I do know the earlier form
was phased out fairly quickly.

TTFN - Guy

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