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From: Dan Cross <crossd@gmail.com>
To: John Cowan <cowan@ccil.org>
Cc: The TUHS <tuhs@tuhs.org>
Subject: Re: [TUHS] Memory management in Dennis Ritchie's C Compiler
Date: Mon, 24 Aug 2020 13:20:43 -0400	[thread overview]
Message-ID: <CAEoi9W6iyOJH93ODeZC6LmRK6Yu4PbCmpkncFJtHZv1c0JZjEw@mail.gmail.com> (raw)
In-Reply-To: <CAD2gp_QkJokBCTBGirhtFr8b_kHMVP_Owv1okcRd74m9Tks7KQ@mail.gmail.com>

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On Mon, Aug 24, 2020 at 1:08 PM John Cowan <cowan@ccil.org> wrote:

> On Mon, Aug 24, 2020 at 12:00 PM Dan Cross <crossd@gmail.com> wrote:
>
>> Stacks may be at the top of the user portion of the address space; but
>> I'd have to double check the details.
>>
>
> That's always true on the PDP-11 and Vax, no matter what the OS, because
> the processor architecture (which has pre-increment and post-decrement
> instructions, but not their counterparts) makes anything but a
> downward-growing stack unmanageable.
>

Ah, but if one has a fixed-size stack that cannot be extended, one can put
it anywhere one wants in the virtual address space. E.g., right after the
program text segment or whatever (effectively using the text as a guard to
detect stack overflow). I don't know why one would want to do that, except
that it makes freeing the virtual address space slightly simpler when the
process exits, but the point is that the Unix choice isn't the only way.
That said, stacks and data growing toward each gives the maximum amount of
flexibility.

In OSes without virtual memory like RSX-11[ABC], RT-11, and
> mini-Unix/LSX-11, what counts as the top naturally varies.
>
> Dennis's compiler AFAIK was never extended to anything but the PDP-11,
> both as host and target.
>

That's my impression, as well.

        - Dan C.

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  parent reply	other threads:[~2020-08-24 17:21 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-15 21:50 Dibyendu Majumdar
2020-08-16 15:20 ` arnold
2020-08-16 15:27   ` Jim Geist
2020-08-17 16:13 ` Dan Cross
2020-08-17 20:16   ` Dibyendu Majumdar
2020-08-17 20:34     ` Paul Winalski
2020-08-17 20:43       ` Dibyendu Majumdar
2020-08-17 21:05         ` Warner Losh
2020-08-17 22:47         ` Dave Horsfall
2020-08-17 23:06           ` Nemo Nusquam
2020-08-17 21:29     ` Dibyendu Majumdar
2020-08-24 15:58     ` Dan Cross
2020-08-24 17:08       ` John Cowan
2020-08-24 17:15         ` Clem Cole
2020-08-24 17:24           ` Clem Cole
2020-08-24 17:20         ` Dan Cross [this message]
2020-08-25 23:06           ` Arthur Krewat
2020-08-17  2:02 Noel Chiappa
2020-08-17 18:02 ` Paul Winalski
2020-08-17 18:13   ` Jim Geist
2020-08-17 18:48     ` Paul Winalski
2020-08-17 19:08       ` Jim Geist
2020-08-17 19:28         ` Paul Winalski
2020-08-17 19:35           ` Jim Geist
2020-08-17 19:41             ` Richard Salz
2020-08-17 23:40               ` Steffen Nurpmeso
2020-08-17 19:27 Noel Chiappa
2020-08-17 19:30 ` Larry McVoy
2020-08-17 19:44   ` Dan Halbert
2020-08-17 19:50   ` Paul Winalski
2020-08-17 22:05     ` Arthur Krewat
2020-08-18  0:52 ` Rob Gingell
2020-08-17 19:51 Noel Chiappa
2020-08-17 22:32 Norman Wilson
2020-08-17 22:55 ` Bakul Shah
2020-08-17 23:12 ` Chet Ramey
2020-08-18  6:33 ` arnold
2020-08-25  9:36 Steve Simon
2020-08-26 13:24 Doug McIlroy
2020-08-26 15:41 ` John Cowan
2020-08-26 15:59 Noel Chiappa
2020-08-26 16:09 ` Warner Losh
2020-08-26 19:13   ` Clem Cole
2020-08-26 16:14 ` Jim Geist
2020-08-26 17:31 ` John Cowan
2020-08-27  8:37 Paul Ruizendaal

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