Re: [Qemu-devel] [PATCH 04/11] qerror: Eliminate QERR_DEVICE_NOT_FOUND

[Markus Armbruster <armbru@redhat.com>]

Eric Blake <eblake@redhat.com> writes:

> On 06/15/2015 09:18 AM, Luiz Capitulino wrote:
>> On Sat, 13 Jun 2015 16:20:51 +0200
>> Markus Armbruster <armbru@redhat.com> wrote:
>> 
>>> Error classes other than ERROR_CLASS_GENERIC_ERROR should not be used
>>> in new code.  Hiding them in QERR_ macros makes new uses hard to spot.
>>> Fortunately, there's just one such macro left.  Eliminate it with this
>>> coccinelle semantic patch:
>>>
>>>     @@
>>>     expression EP, E;
>>>     @@
>>>     -error_set(EP, QERR_DEVICE_NOT_FOUND, E)
>>>     +error_set(EP, ERROR_CLASS_DEVICE_NOT_FOUND, "Device '%s' not found", E)
>> 
>> This is a bit minor, but I think I'd have created a new function instead,
>> say error_set_enodev(). This avoids all the duplication. But I'm not asking
>> you to change, as the patch is good and this can be done in the future if
>> we so want.
>
> In fact, in both patch 4 and 5, I thought a similar thing - the
> remaining QERR_ macros that contain a % embedded in them are a bit
> unusual (when reading error_setg(), you have to go look up the QERR_
> macro to see how many arguments you should really be passing).  If I
> understand correctly, one of the reasons we went with QERR_ macros
> embedding % was to ensure consistent error messages among multiple call
> sites, in part if we want to enable error message translations (but
> that's a bigger project anyways, which you have argued that we may not
> even want).
>
> Having helper functions for the more common error messages can both
> reduce confusion (no hidden %) and duplication (callers don't need to
> repeat the same string).  But I likewise agree with Luiz that it can be
> deferred to the future if desired.

My preferred solution is to have a helper function for the *action*
rather than just its error.  Not always practical.