One thing that was supported on PCC for many years was the ability to
generate GE/Honeywell 6-bit character constants, using the back quote
(`) character.  I remember trying it in the late 80's on a shipping
Sun machine and seeing that it was still present in the grammar, and,
as nearly as I could remember, still produced the correct answer.

Steve

----- Original Message -----
From: "Lars Brinkhoff" <lars@nocrew.org>
To:"Warner Losh" <imp@bsdimp.com>
Cc:"Steve Johnson" <scj@yaccman.com>, "The Eunuchs Hysterical Society"
<tuhs@tuhs.org>
Sent:Tue, 30 Oct 2018 08:16:17 +0000
Subject:Re: [TUHS] Archaic yacc C grammar

 Warner Losh wrote:
 > Steve Johnson wrote:
 > We actually had a pretty good system for making changes like
 > that. First, we would change the compiler to accept both the old
and
 > the new. Then we would produce a warning that on a particular date
 > the old would no longer work. Then we made the old an error and
 > printed a message about how to fix it.
 >
 > How long a transition period did you typically have?

 I heard the V7 compiler still supports old B style initialization
 "int x 42;". So in some cases, a really long time.