Re: [Qemu-devel] [PATCH 01/11] qemu-img: introduce qemu_img_handle_error()

[Luiz Capitulino <lcapitulino@redhat.com>]

On Thu, 18 Apr 2013 15:09:27 +0200
Pavel Hrdina <phrdina@redhat.com> wrote:

> On 18.4.2013 14:59, Kevin Wolf wrote:
> > Am 18.04.2013 um 13:52 hat Pavel Hrdina geschrieben:
> >> On 18.4.2013 13:44, Kevin Wolf wrote:
> >>> Am 16.04.2013 um 18:05 hat Pavel Hrdina geschrieben:
> >>>> Later in the patch series we will use this function few times.
> >>>> This will avoid of duplicating the code.
> >>>>
> >>>> Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
> >>>> ---
> >>>>   qemu-img.c | 17 +++++++++++------
> >>>>   1 file changed, 11 insertions(+), 6 deletions(-)
> >>>>
> >>>> diff --git a/qemu-img.c b/qemu-img.c
> >>>> index 31627b0..dbacdb7 100644
> >>>> --- a/qemu-img.c
> >>>> +++ b/qemu-img.c
> >>>> @@ -322,6 +322,16 @@ static int add_old_style_options(const char *fmt, QEMUOptionParameter *list,
> >>>>       return 0;
> >>>>   }
> >>>>
> >>>> +static int qemu_img_handle_error(const char *msg, Error *err)
> >>>> +{
> >>>> +    if (error_is_set(&err)) {
> >>>> +        error_report("%s: %s", msg, error_get_pretty(err));
> >>>> +        error_free(err);
> >>>> +        return 1;
> >>>> +    }
> >>>> +    return 0;
> >>>> +}
> >>>> +
> >>>>   static int img_create(int argc, char **argv)
> >>>>   {
> >>>>       int c;
> >>>> @@ -400,13 +410,8 @@ static int img_create(int argc, char **argv)
> >>>>
> >>>>       bdrv_img_create(filename, fmt, base_filename, base_fmt,
> >>>>                       options, img_size, BDRV_O_FLAGS, &local_err, quiet);
> >>>> -    if (error_is_set(&local_err)) {
> >>>> -        error_report("%s", error_get_pretty(local_err));
> >>>> -        error_free(local_err);
> >>>> -        return 1;
> >>>> -    }
> >>>>
> >>>> -    return 0;
> >>>> +    return qemu_img_handle_error("qemu-img create failed", local_err);
> >>>>   }
> >>>
> >>> This makes a change to the error message that isn't mentioned in the
> >>> commit message. It should definitely be mentioned there, but I'm not
> >>> even sure if it's a good change. Today you get something like:
> >>>
> >>>      $ qemu-img create -f foo test.img
> >>>      qemu-img: Unknown file format 'foo'
> >>>
> >>> With the patch applied it becomes:
> >>>
> >>>      $ qemu-img create -f foo test.img
> >>>      qemu-img: qemu-img create failed: Unknown file format 'foo'
> >>>
> >>> Does this add any useful information or does it just make the error
> >>> message longer? I feel it's the latter.
> >>>
> >>> Kevin
> >>>
> >>
> >> Thanks for pointing this out, it should be
> >> qemu_img_handle_error("create failed", local_err);
> >>
> >> and later in patch series also
> >> qemu_img_handle_error("snapshot create failed", local_err);
> >>
> >> Is that OK after this change?
> >
> > I would in fact leave the error message as it is today. The "create
> > failed" doesn't help me understand the error better. I already know that
> > it's a create command that failed, because it was me who called 'qemu-img
> > create'.
> >
> > Kevin
> >
> 
> Yes that's true and make sense, but what if another tool internally uses 
> the qemu-img command? I know that the tool could print/return/whatever 
> proper error message, but qemu-img could help with that printing more 
> information.

Then the tool should prepend any relevant information. We can't guess
all use cases.