From: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
To: "Marc-André Lureau" <marcandre.lureau@gmail.com>
Cc: qemu-devel@nongnu.org, "Hyman Huang" <yong.huang@smartx.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Gerd Hoffmann" <kraxel@redhat.com>,
qemu-block@nongnu.org, "Kevin Wolf" <kwolf@redhat.com>,
"Fabiano Rosas" <farosas@suse.de>,
"Mahmoud Mandour" <ma.mandourr@gmail.com>,
"John Snow" <jsnow@redhat.com>,
"Klaus Jensen" <its@irrelevant.dk>, "Fam Zheng" <fam@euphon.net>,
"Eugenio Pérez" <eperezma@redhat.com>,
"Bin Meng" <bin.meng@windriver.com>,
"Hanna Reitz" <hreitz@redhat.com>,
"Eric Blake" <eblake@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
"Stefan Hajnoczi" <stefanha@redhat.com>,
"Philippe Mathieu-Daudé" <philmd@linaro.org>,
"Yuval Shaia" <yuval.shaia.ml@gmail.com>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Jesper Devantier" <foss@defmacro.it>,
"Pierrick Bouvier" <pierrick.bouvier@linaro.org>,
"Keith Busch" <kbusch@kernel.org>,
"Marcel Apfelbaum" <marcel.apfelbaum@gmail.com>,
"Alexandre Iooss" <erdnaxe@crans.org>,
"Peter Xu" <peterx@redhat.com>
Subject: Re: [PATCH 06/19] block/stream: fix -Werror=maybe-uninitialized false-positives
Date: Tue, 2 Apr 2024 12:58:43 +0300 [thread overview]
Message-ID: <0d7344c2-b146-44cf-a911-21fa5e556665@yandex-team.ru> (raw)
In-Reply-To: <CAJ+F1CLbjZG24rMKwA20NFM=6sTE4CRAaGt4Vha+bP8i=+on-A@mail.gmail.com>
On 02.04.24 12:12, Marc-André Lureau wrote:
> Hi
>
> On Fri, Mar 29, 2024 at 12:35 PM Vladimir Sementsov-Ogievskiy
> <vsementsov@yandex-team.ru> wrote:
>>
>> On 28.03.24 13:20, marcandre.lureau@redhat.com wrote:
>>> From: Marc-André Lureau <marcandre.lureau@redhat.com>
>>>
>>> ../block/stream.c:193:19: error: ‘unfiltered_bs’ may be used uninitialized [-Werror=maybe-uninitialized]
>>> ../block/stream.c:176:5: error: ‘len’ may be used uninitialized [-Werror=maybe-uninitialized]
>>> trace/trace-block.h:906:9: error: ‘ret’ may be used uninitialized [-Werror=maybe-uninitialized]
>>>
>>> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
>>
>> Again, same false-positives, because of WITH_GRAPH_RDLOCK_GUARD()..
>>
>> Didn't you try to change WITH_ macros somehow, so that compiler believe in our good intentions?
>>
>
>
> #define WITH_QEMU_LOCK_GUARD_(x, var) \
> for (g_autoptr(QemuLockable) var = \
> qemu_lockable_auto_lock(QEMU_MAKE_LOCKABLE_NONNULL((x))); \
> var; \
> qemu_lockable_auto_unlock(var), var = NULL)
>
> I can't think of a clever way to rewrite this. The compiler probably
> thinks the loop may not run, due to the "var" condition. But how to
> convince it otherwise? it's hard to introduce another variable too..
hmm. maybe like this?
#define WITH_QEMU_LOCK_GUARD_(x, var) \
for (g_autoptr(QemuLockable) var = \
qemu_lockable_auto_lock(QEMU_MAKE_LOCKABLE_NONNULL((x))), \
var2 = (void *)(true); \
var2; \
qemu_lockable_auto_unlock(var), var2 = NULL)
probably, it would be simpler for compiler to understand the logic this way. Could you check?
(actually, will also need to construct var2 name same way as for var)
>
>> Actually, "unused variable initialization" is bad thing too.
>>
>> Anyway, if no better solution for now:
>> Acked-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
>>
>>> ---
>>> block/stream.c | 6 +++---
>>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/block/stream.c b/block/stream.c
>>> index 7031eef12b..9076203193 100644
>>> --- a/block/stream.c
>>> +++ b/block/stream.c
>>> @@ -155,8 +155,8 @@ static void stream_clean(Job *job)
>>> static int coroutine_fn stream_run(Job *job, Error **errp)
>>> {
>>> StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
>>> - BlockDriverState *unfiltered_bs;
>>> - int64_t len;
>>> + BlockDriverState *unfiltered_bs = NULL;
>>> + int64_t len = -1;
>>> int64_t offset = 0;
>>> int error = 0;
>>> int64_t n = 0; /* bytes */
>>> @@ -177,7 +177,7 @@ static int coroutine_fn stream_run(Job *job, Error **errp)
>>>
>>> for ( ; offset < len; offset += n) {
>>> bool copy;
>>> - int ret;
>>> + int ret = -1;
>>>
>>> /* Note that even when no rate limit is applied we need to yield
>>> * with no pending I/O here so that bdrv_drain_all() returns.
>>
>> --
>> Best regards,
>> Vladimir
>>
>>
>
>
--
Best regards,
Vladimir
next prev parent reply other threads:[~2024-04-02 10:00 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-28 10:20 [PATCH 00/19] -Werror=maybe-uninitialized fixes marcandre.lureau
2024-03-28 10:20 ` [PATCH 01/19] util/coroutine: fix -Werror=maybe-uninitialized false-positive marcandre.lureau
2024-04-02 20:17 ` Stefan Hajnoczi
2024-03-28 10:20 ` [PATCH 02/19] util/timer: with " marcandre.lureau
2024-03-28 10:20 ` [PATCH 03/19] hw/qxl: fix -Werror=maybe-uninitialized false-positives marcandre.lureau
2024-03-28 10:20 ` [PATCH 04/19] nbd: with -Werror=maybe-uninitialized false-positive marcandre.lureau
2024-03-28 14:30 ` Eric Blake
2024-03-28 10:20 ` [PATCH 05/19] block/mirror: fix " marcandre.lureau
2024-03-29 8:22 ` Vladimir Sementsov-Ogievskiy
2024-03-28 10:20 ` [PATCH 06/19] block/stream: fix -Werror=maybe-uninitialized false-positives marcandre.lureau
2024-03-29 8:34 ` Vladimir Sementsov-Ogievskiy
2024-04-02 9:12 ` Marc-André Lureau
2024-04-02 9:58 ` Vladimir Sementsov-Ogievskiy [this message]
2024-04-02 15:34 ` Eric Blake
2024-04-02 19:24 ` Vladimir Sementsov-Ogievskiy
2024-04-03 8:11 ` Marc-André Lureau
2024-04-03 8:31 ` Vladimir Sementsov-Ogievskiy
2024-04-03 9:24 ` Marc-André Lureau
2024-04-03 17:50 ` Eric Blake
2024-04-03 21:28 ` Vladimir Sementsov-Ogievskiy
2024-03-28 10:20 ` [PATCH 07/19] hw/ahci: fix -Werror=maybe-uninitialized false-positive marcandre.lureau
2024-03-28 10:20 ` [PATCH 08/19] hw/vhost-scsi: fix -Werror=maybe-uninitialized marcandre.lureau
2024-03-28 10:20 ` [PATCH 09/19] hw/sdhci: fix -Werror=maybe-uninitialized false-positive marcandre.lureau
2024-03-28 11:30 ` Philippe Mathieu-Daudé
2024-04-02 9:21 ` Marc-André Lureau
2024-03-28 10:20 ` [PATCH 10/19] hw/rdma: " marcandre.lureau
2024-03-28 10:20 ` [PATCH 11/19] migration/block: " marcandre.lureau
2024-03-28 19:40 ` Peter Xu
2024-03-28 10:20 ` [PATCH 12/19] migration: fix -Werror=maybe-uninitialized false-positives marcandre.lureau
2024-03-28 19:40 ` Peter Xu
2024-03-29 1:14 ` Yong Huang
2024-03-28 10:20 ` [PATCH 13/19] hw/virtio-blk: fix -Werror=maybe-uninitialized false-positive marcandre.lureau
2024-04-02 20:18 ` Stefan Hajnoczi
2024-03-28 10:20 ` [PATCH 14/19] plugins: " marcandre.lureau
2024-03-28 10:35 ` Pierrick Bouvier
2024-03-28 10:20 ` [PATCH 15/19] migration: " marcandre.lureau
2024-03-28 19:40 ` Peter Xu
2024-03-28 10:20 ` [PATCH 16/19] tests: fix -Werror=maybe-uninitialized marcandre.lureau
2024-03-28 10:20 ` [PATCH 17/19] hw/nvme: " marcandre.lureau
2024-04-02 10:40 ` Klaus Jensen
2024-03-28 10:20 ` [PATCH 18/19] hw/virtio: " marcandre.lureau
2024-03-28 10:20 ` [PATCH 19/19] RFC: hw/virtio: a potential leak fix marcandre.lureau
2024-03-28 14:31 ` [PATCH 00/19] -Werror=maybe-uninitialized fixes Eric Blake
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