From: Peter Zijlstra <peterz@infradead.org>
To: Maxime COQUELIN <maxime.coquelin@st.com>
Cc: gong.chen@linux.intel.com, Ingo Molnar <mingo@kernel.org>,
" Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
tytso@mit.edu, linux-kernel@vger.kernel.org,
stable@vger.kernel.org, kernel@stlinux.com, eric.paire@st.com
Subject: Re: [PATCH v2] bitops: Fix shift overflow in GENMASK macros
Date: Tue, 4 Nov 2014 11:44:14 +0100 [thread overview]
Message-ID: <20141104104414.GL3337@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1415095437-28723-1-git-send-email-maxime.coquelin@st.com>
On Tue, Nov 04, 2014 at 11:03:57AM +0100, Maxime COQUELIN wrote:
> -#define GENMASK(h, l) (((U32_C(1) << ((h) - (l) + 1)) - 1) << (l))
> -#define GENMASK_ULL(h, l) (((U64_C(1) << ((h) - (l) + 1)) - 1) << (l))
> +#define GENMASK(h, l) ((~0UL >> (BITS_PER_LONG - (h - l + 1))) << l)
> +#define GENMASK_ULL(h, l) ((~0ULL >> (BITS_PER_LONG_LONG - (h - l + 1))) << l)
OK, so you need to keep the (h) and (l) bits, macro arguments should be
wrapped in seemingly superfluous braces in order to preserve precedence
on expansion.
My bad for not explicitly doing that when suggesting the alternative.
next prev parent reply other threads:[~2014-11-04 10:44 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-04 10:03 [PATCH v2] bitops: Fix shift overflow in GENMASK macros Maxime COQUELIN
2014-11-04 10:44 ` Peter Zijlstra [this message]
2014-11-04 10:47 ` Maxime Coquelin
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