From: Chris Friesen <cfriesen@nortelnetworks.com>
To: Linus Torvalds <torvalds@transmeta.com>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: user-mode port 0.44-2.4.7
Date: Wed, 25 Jul 2001 19:37:20 -0400 [thread overview]
Message-ID: <3B5F5830.253C2E0D@nortelnetworks.com> (raw)
In-Reply-To: <Pine.LNX.4.33.0107251615430.22383-100000@penguin.transmeta.com>
Linus Torvalds wrote:
>
> On Thu, 26 Jul 2001, Andrea Arcangeli wrote:
> >
> > I will if Honza assures me that no future version of gcc will cause me to
> > crash if I don't declare xtime volatile and I play with it while it can
> > change under me (which seems not the case from his last email).
>
> WHY DO YOU NOT ADD THE "VOLATILE" TO THE PLACES THAT _CARE_?
>
> This is not a gcc issue. Even if gcc _were_ to generate bad code, the
> global volatile _still_ wouldn't be the correct answer.
I think his worry is the pedantic reason that without the volatile gcc is
allowed to write code that chokes and dies if xtime happens to change in a
volatile manner. The example given earlier was:
code as written:
kprintf("%d\n",xtime.tv_usec);
code as compiled by gcc (with xtime not specified as volatile):
suseconds_t temp = xtime.tv_usec;
if (temp != xtime.tv_usec)
BUG();
kprintf"%d\n",temp);
I hope that gcc would not do such a thing, but I think a case could be made that
it could do it and still comply with the language standard.
Of course, since the linux kernel is an important thing for gcc to compile, I
can't imagine them doing something that would break it on purpose without a
really good reason.
Chris
--
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Nepean, ON K2H 8E9 Canada | email: cfriesen@nortelnetworks.com
next prev parent reply other threads:[~2001-07-25 23:38 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-07-23 5:08 user-mode port 0.44-2.4.7 Jeff Dike
2001-07-23 15:56 ` Andrea Arcangeli
2001-07-23 15:59 ` Andrea Arcangeli
2001-07-23 16:17 ` Andrea Arcangeli
2001-07-23 16:51 ` Andrea Arcangeli
2001-07-23 16:33 ` Linus Torvalds
2001-07-23 16:45 ` Andrea Arcangeli
2001-07-23 17:32 ` Linus Torvalds
2001-07-23 17:50 ` Andrea Arcangeli
2001-07-23 18:11 ` Linus Torvalds
2001-07-23 18:27 ` Andrea Arcangeli
2001-07-23 20:00 ` Linus Torvalds
2001-07-23 20:15 ` Jonathan Lundell
2001-07-23 22:51 ` Linus Torvalds
2001-07-24 3:45 ` Jonathan Lundell
2001-07-24 15:41 ` Davide Libenzi
2001-07-24 15:46 ` Alexander Viro
2001-07-24 16:01 ` Davide Libenzi
2001-07-24 16:08 ` Alexander Viro
2001-07-24 16:52 ` Davide Libenzi
2001-07-24 16:59 ` Linus Torvalds
2001-07-24 17:31 ` Davide Libenzi
2001-07-24 17:38 ` Linus Torvalds
2001-07-24 18:07 ` Anton Altaparmakov
2001-07-23 20:44 ` Chris Friesen
2001-07-23 21:11 ` Andrea Arcangeli
2001-07-23 21:50 ` Richard Gooch
2001-07-23 22:09 ` Andrea Arcangeli
2001-07-23 13:20 ` Rob Landley
2001-07-23 22:27 ` Andrea Arcangeli
2001-07-23 17:50 ` Rob Landley
2001-07-23 23:47 ` Richard Gooch
2001-07-24 0:04 ` Andrea Arcangeli
2001-07-24 9:02 ` Jan Hubicka
2001-07-24 15:35 ` Linus Torvalds
2001-07-24 16:04 ` Linus Torvalds
2001-07-25 22:49 ` Andrea Arcangeli
2001-07-25 23:16 ` Linus Torvalds
2001-07-25 23:37 ` Chris Friesen [this message]
2001-07-26 18:28 ` Jan Hubicka
2001-07-26 18:35 ` Alan Cox
2001-07-23 22:53 ` Linus Torvalds
2001-07-23 23:13 ` Alan Cox
2001-07-23 20:25 ` Jeff Dike
[not found] <no.id>
2001-07-23 20:57 ` Alan Cox
2001-07-23 21:14 ` Chris Friesen
2001-07-25 19:12 ` Alan Cox
2001-07-25 23:49 ` Alan Cox
2001-07-25 19:03 James W. Lake
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