Peter Maydell <peter.mayd...@linaro.org> writes:
> On Wed, 1 Apr 2020 at 10:03, Markus Armbruster <arm...@redhat.com> wrote:
>>
>> QEMU's Error was patterned after GLib's GError. Differences include:
>
> From my POV the major problem with Error as we have it today
> is that it makes the simple process of writing code like
> device realize functions horrifically boilerplate heavy;
> for instance this is from hw/arm/armsse.c:
>
> object_property_set_link(cpuobj, OBJECT(&s->cpu_container[i]),
> "memory", &err);
> if (err) {
> error_propagate(errp, err);
> return;
> }
> object_property_set_link(cpuobj, OBJECT(s), "idau", &err);
> if (err) {
> error_propagate(errp, err);
> return;
> }
> object_property_set_bool(cpuobj, true, "realized", &err);
> if (err) {
> error_propagate(errp, err);
> return;
> }
>
> 16 lines of code just to set 2 properties on an object
> and realize it. It's a lot of boilerplate and as
> a result we frequently get it wrong or take shortcuts
> (eg forgetting the error-handling entirely, calling
> error_propagate just once for a whole sequence of
> calls, taking the lazy approach and using err_abort
> or err_fatal when we ought really to be propagating
> an error, etc). I haven't looked at 'auto propagation'
> yet, hopefully it will help?
With that, you can have
object_property_set_link(cpuobj, OBJECT(&s->cpu_container[i]),
"memory", errp);
if (*errp) {
return;
}
object_property_set_link(cpuobj, OBJECT(s), "idau", errp);
if (*errp) {
return;
}
object_property_set_bool(cpuobj, true, "realized", errp);
if (*errp) {
return;
}
but you have to add
ERRP_AUTO_PROPAGATE();
right at the beginning of the function.
It's a small improvement. A bigger one is
if (object_property_set_link(cpuobj, OBJECT(&s->cpu_container[i]),
"memory", errp)) {
return;
}
if (object_property_set_link(cpuobj, OBJECT(s), "idau", errp)) {
return;
}
if (object_property_set_bool(cpuobj, true, "realized", errp)) {
return;
}
This is item "Return value conventions" in the message you replied to.
Elsewhere in this thread, I discussed the difficulties of automating the
conversion to this style. I think I know how to automate converting the
calls to use the bool return value, but converting the functions to
return it looks hard. We could do that manually for a modest set of
frequently used functions. object.h would top my list.
