From: Al Viro <viro@ZenIV.linux.org.uk>
To: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: linux-sparse@vger.kernel.org, Christopher Li <sparse@chrisli.org>
Subject: Re: [PATCH] fix typing error in compound assignment
Date: Sat, 10 Dec 2016 02:14:00 +0000 [thread overview]
Message-ID: <20161210021400.GG1555@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20161207143342.88825-1-luc.vanoostenryck@gmail.com>
On Wed, Dec 07, 2016 at 03:33:42PM +0100, Luc Van Oostenryck wrote:
> But what is really done currently is something like:
> x = x + (typeof(x)) a;
> In other words, the left-hand side is casted to the same type as the
> rhs and the operation is always done with this type, neglecting the
> usual conversions and thus forcing the operation to always be done
> with the rhs type, here 'int' instead of 'long'.
Addition is a bad example, actually - your variant (promotions + operaton +
cast down to the first argument due to assignment) will yield the same value.
It's division where the real trouble happens -
unsigned n1 = 1, n2 = 1;
long v = -1;
n1 /= v;
n2 /= (unsigned)v;
should yield n1 == ~0U, n2 == 0. And yes, the current logics in sparse
does not distinguish between those. So ACK on the fix, but you want
a better testcase.
next prev parent reply other threads:[~2016-12-10 2:14 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-07 14:33 [PATCH] fix typing error in compound assignment Luc Van Oostenryck
2016-12-10 2:14 ` Al Viro [this message]
2016-12-10 6:25 ` Luc Van Oostenryck
-- strict thread matches above, loose matches on Subject: below --
2016-12-10 9:52 Luc Van Oostenryck
2016-12-10 21:22 ` Ramsay Jones
2016-12-10 22:40 ` Luc Van Oostenryck
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