On Wed, Nov 30, 2011 at 03:03:32PM -0600, Anthony Liguori wrote:
> +static void qdev_set_legacy_property(DeviceState *dev, Visitor *v, void
> *opaque,
> + const char *name, Error **errp)
> +{
> + Property *prop = opaque;
> +
> + if (dev->state != DEV_STATE_CREATED) {
> + error_set(errp, QERR_PERMISSION_DENIED);
> + return;
> + }
> +
> + if (prop->info->parse) {
> + Error *local_err = NULL;
> + char *ptr = NULL;
> +
> + visit_type_str(v, &ptr, name, &local_err);
> + if (!local_err) {
> + int ret;
> + ret = prop->info->parse(dev, prop, ptr);
> + if (ret != 0) {
> + error_set(errp, QERR_INVALID_PARAMETER_VALUE,
> + name, prop->info->name);
> + }
> + g_free(ptr);
> + } else {
> + error_propagate(errp, local_err);
> + }
I noticed something subtle about Error** here. Your code is correct but
I (incorrectly) wanted to eliminate local_err and use errp directly:
if (prop->info->parse) {
char *ptr = NULL;
visit_type_str(v, &ptr, name, errp);
if (!error_is_set(errp)) {
int ret;
ret = prop->info->parse(dev, prop, ptr);
if (ret != 0) {
error_set(errp, QERR_INVALID_PARAMETER_VALUE,
name, prop->info->name);
}
g_free(ptr);
}
} else {
...
Turns out you cannot do this because error_is_set(errp) will be false if
the caller passed in a NULL errp. That means we wouldn't detect the
error from visit_type_str()!
So it's not okay to depend on the caller's errp. We always need to
juggle around a local_err with propagation :(.
Just wanted to share.
