On Thu, Apr 02, 2020 at 07:54:11AM +0200, Markus Armbruster wrote:
> 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.
Even better, we can then string the checks together
if (object_property_set_link(cpuobj, OBJECT(&s->cpu_container[i]),
"memory", errp) ||
object_property_set_link(cpuobj, OBJECT(s), "idau", errp) ||
object_property_set_bool(cpuobj, true, "realized", errp)) {
return;
}
Regards,
Daniel
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