Re: [Qemu-devel] [PATCH v2 05/15] qdev_prop_parse(): change return type to void

[Markus Armbruster]

Luiz Capitulino <address@hidden> writes:

> On Thu, 7 Feb 2013 15:12:22 -0200
> Eduardo Habkost <address@hidden> wrote:
>
>> On Tue, Feb 05, 2013 at 09:39:18PM +0100, Laszlo Ersek wrote:
>> > Problems are now reported via Error only.
>> > 
>> > Signed-off-by: Laszlo Ersek <address@hidden>
>> > ---
>> >  hw/qdev-properties.h |    4 ++--
>> >  hw/qdev-monitor.c    |    3 ++-
>> >  hw/qdev-properties.c |   14 ++++++--------
>> >  3 files changed, 10 insertions(+), 11 deletions(-)
>> > 
>> > diff --git a/hw/qdev-properties.h b/hw/qdev-properties.h
>> > index 0fe4030..43fd11a 100644
>> > --- a/hw/qdev-properties.h
>> > +++ b/hw/qdev-properties.h
>> > @@ -100,8 +100,8 @@ extern PropertyInfo qdev_prop_pci_host_devaddr;
>> >  
>> >  /* Set properties between creation and init.  */
>> >  void *qdev_get_prop_ptr(DeviceState *dev, Property *prop);
>> > -int qdev_prop_parse(DeviceState *dev, const char *name, const char *value,
>> > -                    Error **errp);
>> > +void qdev_prop_parse(DeviceState *dev, const char *name, const char 
>> > *value,
>> > +                     Error **errp);
>> >  void qdev_prop_set_bit(DeviceState *dev, const char *name, bool value);
>> >  void qdev_prop_set_uint8(DeviceState *dev, const char *name, uint8_t 
>> > value);
>> >  void qdev_prop_set_uint16(DeviceState *dev, const char *name, uint16_t 
>> > value);
>> > diff --git a/hw/qdev-monitor.c b/hw/qdev-monitor.c
>> > index 5eb1c8c..cf96046 100644
>> > --- a/hw/qdev-monitor.c
>> > +++ b/hw/qdev-monitor.c
>> > @@ -110,7 +110,8 @@ static int set_property(const char *name, const char 
>> > *value, void *opaque)
>> >      if (strcmp(name, "bus") == 0)
>> >          return 0;
>> >  
>> > -    if (qdev_prop_parse(dev, name, value, &err) == -1) {
>> > +    qdev_prop_parse(dev, name, value, &err);
>> > +    if (error_is_set(&err)) {
>> 
>> You can use "if (err)" instead. I believe it is acceptable, as there's
>> lots of (recently introduced) QEMU code using this style.
>
> Yes, people tend to use if (err) in new code. For me it honestly doesn't
> matter much, although I wonder if we should have a more strict rule for this.

I prefer plain "if (err)".

>> >          qerror_report_err(err);
>> >          error_free(err);
>> >          return -1;
>> > diff --git a/hw/qdev-properties.c b/hw/qdev-properties.c
>> > index 8e3d014..d94909e 100644
>> > --- a/hw/qdev-properties.c
>> > +++ b/hw/qdev-properties.c
>> > @@ -835,8 +835,8 @@ void error_set_from_qdev_prop_error(Error **errp, int 
>> > ret, DeviceState *dev,
>> >      }
>> >  }
>> >  
>> > -int qdev_prop_parse(DeviceState *dev, const char *name, const char *value,
>> > -                    Error **errp)
>> > +void qdev_prop_parse(DeviceState *dev, const char *name, const char 
>> > *value,
>> > +                     Error **errp)
>> >  {
>> >      char *legacy_name;
>> >      Error *err = NULL;
>> > @@ -849,11 +849,7 @@ int qdev_prop_parse(DeviceState *dev, const char 
>> > *name, const char *value,
>> >      }
>> >      g_free(legacy_name);
>> >  
>> > -    if (err) {
>> > -        error_propagate(errp, err);
>> > -        return -1;
>> > -    }
>> > -    return 0;
>> > +    error_propagate(errp, err);
>> 
>> I didn't expect it to be valid to call error_propagate() if error is
>> _not_ set. All cases of error_propagate() usage I have seen before first
>> checked if error was set. But by looking at the implementation, it seems
>> to be OK.

Yes, it does the right thing.  Weaker preconditions are good :)

>> Maybe we should extend the error_propagate() documentation to mention it
>> is OK to call error_propagate() even if error is unset?

Makes sense.

[...]