Re: [Qemu-devel] [PATCH v6 08/15] qstring: Add qstring_wrap_str()

[Marc-André Lureau]

Hi

On Tue, Oct 11, 2016 at 7:05 PM Eric Blake <address@hidden> wrote:

> On 10/11/2016 10:04 AM, Eric Blake wrote:
> > On 10/11/2016 06:08 AM, Marc-André Lureau wrote:
> >
> >>> +++ b/block.c
> >>> @@ -1640,7 +1640,8 @@ static BlockDriverState
> >>> *bdrv_append_temp_snapshot(BlockDriverState *bs,
> >>>      qdict_put(snapshot_options, "file.driver",
> >>>                qstring_from_str("file"));
> >>>      qdict_put(snapshot_options, "file.filename",
> >>> -              qstring_from_str(tmp_filename));
> >>> +              qstring_wrap_str(tmp_filename));
> >>> +    tmp_filename = NULL;
> >>>      qdict_put(snapshot_options, "driver",
> >>>                qstring_from_str("qcow2"));
> >>>
> >>>
> >> You could also remove g_free(tmp_filename) from the normal return path
> >> (this may please static analyzers).
> >
> > No. g_free(NULL) is safe, but we can also reach the 'out' label with
> > tmp_filename still malloc'd prior to the place where we transfer it
> > here, so the g_free() in the cleanup label is still required.  The
> > assignment to NULL here prevents a double free.  The patch is correct
> as-is.
>
> Spoke too soon.  I see what you're saying - the normal return path now
> has a dead g_free(NULL).  It won't cause any grief to the static
> analyzers, but it is a useless no-op function call, so I can indeed trim
> it (the one before the label, not the one after).
>

static analyzers could  catch the fact that you always call g_free(NULL) in
this code path, please remove it.


> --
> Eric Blake   eblake redhat com    +1-919-301-3266 <+1%20919-301-3266>
> Libvirt virtualization library http://libvirt.org
>
> --
Marc-André Lureau