From: Eric Blake <eblake@redhat.com>
To: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Cc: Richard Henderson <richard.henderson@linaro.org>,
qemu-devel@nongnu.org, qemu-block@nongnu.org
Subject: Re: [PATCH 01/11] nbd/server: Remove unused variable
Date: Tue, 13 Jul 2021 08:14:38 -0500 [thread overview]
Message-ID: <20210713131438.hx2gp6v2jc2qvba3@redhat.com> (raw)
In-Reply-To: <20210713130134.zfti7sgxcw4i3dbd@redhat.com>
On Tue, Jul 13, 2021 at 08:01:34AM -0500, Eric Blake wrote:
> > > @@ -973,7 +973,6 @@ static int nbd_negotiate_meta_queries(NBDClient *client,
> > > {
> > > int ret;
> > > g_autofree char *export_name = NULL;
> > > - g_autofree bool *bitmaps = NULL;
> > > NBDExportMetaContexts local_meta = {0};
> > Actually, "bitmaps" _is_ used, in cleanup handler, setup by g_autofree. So it's a false positive.
> >
>
> Correct; this patch is wrong, and would cause a memory leak. This is a
> false positive in clang, and a known issue that clang is in general
> unable to see that g_autofree variables are used, sometimes for their
> intentional side effects such as easier memory cleanup as done here.
>
> I suspect that the definition of g_autofree already uses
> __attribute__((unused)) to work around clang's oddities, which means
> I'm not sure how to silence clang on this one.
Hmm; in glib 2.68.2 (on Fedora 34), g_autofree does NOT include an
attribute unused. Thus, does this silence the compiler? (Even cooler
would be making the comment a link to an actual bug in the clang
database, but I couldn't quickly find one)
diff --git i/nbd/server.c w/nbd/server.c
index b60ebc3ab6ac..393cbd81c57a 100644
--- i/nbd/server.c
+++ w/nbd/server.c
@@ -973,7 +973,8 @@ static int nbd_negotiate_meta_queries(NBDClient *client,
{
int ret;
g_autofree char *export_name = NULL;
- g_autofree bool *bitmaps = NULL;
+ /* G_GNUC_UNUSED needed to work around a clang bug */
+ g_autofree G_GNUC_UNUSED bool *bitmaps = NULL;
NBDExportMetaContexts local_meta = {0};
uint32_t nb_queries;
size_t i;
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
next prev parent reply other threads:[~2021-07-13 13:16 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-12 21:55 [PATCH 00/11] Fixes for clang-13 plus tcg/ppc Richard Henderson
2021-07-12 21:55 ` [PATCH 01/11] nbd/server: Remove unused variable Richard Henderson
2021-07-13 9:27 ` Vladimir Sementsov-Ogievskiy
2021-07-13 13:01 ` Eric Blake
2021-07-13 13:14 ` Eric Blake [this message]
2021-07-13 13:54 ` Richard Henderson
2021-07-12 21:55 ` [PATCH 02/11] accel/tcg: Remove unused variable in cpu_exec Richard Henderson
2021-07-13 16:27 ` Philippe Mathieu-Daudé
2021-07-12 21:55 ` [PATCH 03/11] util/selfmap: Discard mapping on error Richard Henderson
2021-07-13 16:06 ` Eric Blake
2021-07-13 17:10 ` Richard Henderson
2021-07-12 21:55 ` [PATCH 04/11] net/checksum: Remove unused variable in net_checksum_add_iov Richard Henderson
2021-07-12 21:55 ` [PATCH 05/11] hw/audio/adlib: Remove unused variable in adlib_callback Richard Henderson
2021-07-13 16:31 ` Philippe Mathieu-Daudé
2021-07-12 21:55 ` [PATCH 06/11] hw/ppc/spapr_events: Remove unused variable from check_exception Richard Henderson
2021-07-13 0:05 ` David Gibson
2021-07-12 21:55 ` [PATCH 07/11] hw/pci-hist/pnv_phb4: Fix typo in pnv_phb4_ioda_write Richard Henderson
2021-07-13 0:06 ` David Gibson
2021-07-12 21:55 ` [PATCH 08/11] linux-user/syscall: Remove unused variable from execve Richard Henderson
2021-07-13 13:57 ` Laurent Vivier
2021-07-12 21:55 ` [PATCH 09/11] tests/unit: Remove unused variable from test_io Richard Henderson
2021-07-13 16:30 ` Philippe Mathieu-Daudé
2021-07-12 21:55 ` [PATCH 10/11] tcg/ppc: Replace TCG_TARGET_CALL_DARWIN with _CALL_DARWIN Richard Henderson
2021-07-12 21:55 ` [PATCH 11/11] tcg/ppc: Ensure _CALL_SYSV is set for 32-bit ELF Richard Henderson
2021-08-14 5:27 ` [PATCH 00/11] Fixes for clang-13 plus tcg/ppc Brad Smith
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