[Qemu-devel] error reporting in functions

[Qemu-devel] error reporting in functions

[Vladimir Sementsov-Ogievskiy]

HI all!

My questions is: what are general recommendations in Qemu for return 
code, if we have Error **errp?
What should I prefer: errp, duplicated by int return code, or void 
functions with errp?

void + errp seems good, just to not duplicate things. But it has a 
disadvantage of necessity of "local_err" and "error_propagate" in caller 
function, if its behaviour depends on callee function success...

-- 
Best regards,
Vladimir

Re: [Qemu-devel] error reporting in functions

[Eric Blake]

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On 10/12/2016 10:47 AM, Vladimir Sementsov-Ogievskiy wrote:
> HI all!
> 
> My questions is: what are general recommendations in Qemu for return
> code, if we have Error **errp?
> What should I prefer: errp, duplicated by int return code, or void
> functions with errp?

Markus has already had several threads commenting on this very topic in
the past.  A lot of code uses void return, but some newer code is using
an int return for simplifying the call-sites (and glib prefers the int
rather than void return, as well).  Markus was playing with a Coccinelle
script to see how painful a bulk-conversion of the code base would be,
but it is probably stalled behind more pressing work at the moment.

> 
> void + errp seems good, just to not duplicate things. But it has a
> disadvantage of necessity of "local_err" and "error_propagate" in caller
> function, if its behaviour depends on callee function success...
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] error reporting in functions

[Markus Armbruster]

Eric Blake <eblake@redhat.com> writes:

> On 10/12/2016 10:47 AM, Vladimir Sementsov-Ogievskiy wrote:
>> HI all!
>> 
>> My questions is: what are general recommendations in Qemu for return
>> code, if we have Error **errp?
>> What should I prefer: errp, duplicated by int return code, or void
>> functions with errp?
>
> Markus has already had several threads commenting on this very topic in
> the past.  A lot of code uses void return, but some newer code is using

A recent one:
Message-ID: <87a8ekfenp.fsf@dusky.pond.sub.org>
http://lists.gnu.org/archive/html/qemu-devel/2016-10/msg00435.html

> the past.  A lot of code uses void return, but some newer code is using
> an int return for simplifying the call-sites (and glib prefers the int
> rather than void return, as well).  Markus was playing with a Coccinelle
> script to see how painful a bulk-conversion of the code base would be,
> but it is probably stalled behind more pressing work at the moment.

Correct.

>> void + errp seems good, just to not duplicate things. But it has a
>> disadvantage of necessity of "local_err" and "error_propagate" in caller
>> function, if its behaviour depends on callee function success...