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

[Pavel Hrdina <phrdina@redhat.com>]

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.

Pavel