From: Bakul Shah <bakul+plan9@bitblocks.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Subject: Re: [9fans] BUG!!! in Plan9 compiler!
Date: Fri, 23 Apr 2010 13:08:14 -0700 [thread overview]
Message-ID: <20100423200815.03B385B4A@mail.bitblocks.com> (raw)
In-Reply-To: Your message of "Fri, 23 Apr 2010 19:53:24 BST." <239c41a785c8c5638338c2f007f50733@vitanuova.com>
On Fri, 23 Apr 2010 19:53:24 BST C H Forsyth <forsyth@vitanuova.com> wrote:
> >As per C89 in this case the unsigned char value should be
> >promoted to a *signed* int value. The sum will be of type
> >signed int and so the division will do the right thing. In
> >kencc case it seems the sum has type unsigned int for some
> >reason and further, the signed divisor (2) is promoted to an
> >unsigned int. Seems like a bug.
>
> on 19 April, I wrote:
> >notably the compiler doesn't implement the value-preserving rules for compar
> isons. ...
> >instead the compiler implements the older unsigned-preserving rule
Does the following assertion fail under plan9?
int x = 1234, y = -4321;
unsigned char z = 12;
int r1, r2;
r1 = (x + y + z)/2;
x += z;
r2 = (x + y)/2;
assert(r1 == r2);
If so, I consider it a bug; particularly as there is no
overflow involved anywhere.
next prev parent reply other threads:[~2010-04-23 20:08 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-22 15:29 tlaronde
2010-04-22 17:03 ` Bakul Shah
2010-04-22 17:36 ` tlaronde
2010-04-22 17:50 ` tlaronde
2010-04-22 19:08 ` geoff
2010-04-22 19:32 ` tlaronde
2010-04-22 20:07 ` Bakul Shah
2010-04-22 21:15 ` tlaronde
2010-04-22 21:26 ` tlaronde
2010-04-22 22:49 ` Bakul Shah
2010-04-23 7:42 ` tlaronde
2010-04-23 18:53 ` C H Forsyth
2010-04-23 18:51 ` tlaronde
2010-04-23 20:08 ` Bakul Shah [this message]
2010-04-23 20:46 ` ron minnich
2010-04-23 21:44 ` erik quanstrom
2010-04-23 22:34 ` erik quanstrom
2010-04-24 18:59 ` Bakul Shah
2010-04-24 21:47 ` Charles Forsyth
2010-04-25 0:31 ` erik quanstrom
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