Re: Questionable aspects of QEMU Error's design

[Peter Maydell <peter.maydell@linaro.org>]

On Wed, 1 Apr 2020 at 10:03, Markus Armbruster <armbru@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?

thanks
-- PMM