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Date: Fri, 28 Feb 2014 11:41:06 +0100
From: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20140228104106.GG30385@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v4 4/6] qdev: add get_pointer_and_free()
 for temporary strings
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To: Igor Mammedov <imammedo@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Fam Zheng <famz@redhat.com>, qemu-devel@nongnu.org, Michael Roth <mdroth@linux.vnet.ibm.com>

On Wed, Feb 26, 2014 at 10:53:34AM +0100, Igor Mammedov wrote:
> On Fri, 21 Feb 2014 15:46:56 +0100
> Stefan Hajnoczi <stefanha@redhat.com> wrote:
> 
> > get_pointer() assumes the string has unspecified lifetime (at least as
> > long as the object is alive).  In some cases we can only produce a
> > temporary string that should be freed when get_pointer() is done.
> > 
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > ---
> >  hw/core/qdev-properties-system.c | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> > 
> > diff --git a/hw/core/qdev-properties-system.c b/hw/core/qdev-properties-system.c
> > index 5f5957e..3bffc01 100644
> > --- a/hw/core/qdev-properties-system.c
> > +++ b/hw/core/qdev-properties-system.c
> > @@ -31,6 +31,20 @@ static void get_pointer(Object *obj, Visitor *v, Property *prop,
> >      visit_type_str(v, &p, name, errp);
> >  }
> >  
> > +/* Same as get_pointer() but frees heap-allocated print() return value */
> > +static void get_pointer_and_free(Object *obj, Visitor *v, Property *prop,
> > +                                 char *(*print)(void *ptr),
> > +                                 const char *name, Error **errp)
> > +{
> > +    DeviceState *dev = DEVICE(obj);
> > +    void **ptr = qdev_get_prop_ptr(dev, prop);
> > +    char *p;
> > +
> > +    p = *ptr ? print(*ptr) : g_strdup("");
> > +    visit_type_str(v, &p, name, errp);
> > +    g_free(p);
> > +}
> it could be better if get_pointer() would free pointer if 3 current users
> are converted to return temporary string, something like this:

Yes, that is nicer.  I'll switch to your patch in the next revision.

Stefan