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
