From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: Bruce Richardson <bruce.richardson@intel.com>, yliu@fridaylinux.org
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] vhost: fix false-positive warning from clang 5
Date: Wed, 11 Oct 2017 12:12:07 +0200 [thread overview]
Message-ID: <0a77b5a9-fa1a-6409-2518-5e2738888da9@redhat.com> (raw)
In-Reply-To: <20171011095907.229893-1-bruce.richardson@intel.com>
On 10/11/2017 11:59 AM, Bruce Richardson wrote:
> When compiling with clang extra warning flags, such as used by default with
> meson, a warning is given in iotlb.c:
>
> ../lib/librte_vhost/iotlb.c:318:6: warning: variable 'socket' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
>
> This is a false positive, as the socket value will be initialized by the
> call to get_mempolicy in the case where the NUMA build-time flag is set,
> and in cases where it is not set, "if (ret)" will always be true as ret is
> initialized to -1 and never changed.
>
> However, this is not immediately obvious, and is perhaps a little fragile,
> as it will break if other code using ret is subsequently added above the
> call to get_mempolicy by someone unaware of this subtle dependency.
> Therefore, we can fix the warning and making the code more robust by
> explicitly initializing socket to zero, and moving the extra condition
> check on ret into the #ifdef alongside the call to get_mempolicy which sets
> ret.
>
> Fixes: d012d1f293f4 ("vhost: add IOTLB helper functions")
>
> CC: Maxime Coquelin <maxime.coquelin@redhat.com>
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> ---
> lib/librte_vhost/iotlb.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
I agree this is a bit fragile. Thanks for handling this:
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Thanks,
Maxime
next prev parent reply other threads:[~2017-10-11 10:12 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-11 9:59 Bruce Richardson
2017-10-11 10:12 ` Maxime Coquelin [this message]
2017-10-11 10:51 ` [dpdk-dev] [PATCH] vhost: fix false-positive warning from clang5 Thomas Monjalon
2017-10-11 11:01 ` Bruce Richardson
2017-10-11 11:28 ` [dpdk-dev] [PATCH v2] vhost: fix false-positive warning from clang 5 Bruce Richardson
2017-10-11 12:49 ` Thomas Monjalon
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