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.
----- Original Message -----
"Lars Brinkhoff" <firstname.lastname@example.org>
To:"Warner Losh" <email@example.com>
Cc:"Steve Johnson" <firstname.lastname@example.org>, "The Eunuchs Hysterical Society" <email@example.com>
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.