[systemd-devel] [PATCH 1/2] sd-bus: sd_bus_message_get_errno should only return positive errno

[Lennart Poettering]

On Mon, 15.09.14 23:15, Thomas H.P. Andersen (phomes at gmail.com) wrote:

heya,

> From: Thomas Hindoe Paaboel Andersen <phomes at gmail.com>
> 
> sd_bus_message_get_errno can currently return either a number of
> different poitive errno values (from bus-error-mapping), or a negative
> EINVAL if passed null as parameter.
> 
> The check for null parameter was introduced in 40ca29a1370379d43e44c0ed425eecc7218dcbca
> at the same as the function was renamed from bus_message_to_errno and
> made public API. Before becoming public the function used to return
> only negative values.
> 
> It is weird to have a function return both positive and negative errno
> and it generally looks like a mistake. The function is guarded by the
> --enable-kdbus flags so I wonder if we still have time to fix it up?
> It does not have any documentation yet. However, except for a few details
> it is just a convenient way to call sd_bus_error_get_errno which is documented
> to return only positive errno.
> 
> This patch makes it return only positive errno and fixes up the two
> calls to the function that tried to cope with both positive and negative
> values.

Just for the sake of archives:

So, the original code actually really made some sense. The idea was
that the error code of the error struct passed in would be return
positive, but any errors with the mode of invocation of the function
itself would return negative errors. That way it would be clear how to
distuingish invocation errors from actually translated errors...

Now, this distinction is probably a bit over the top, and certainly
doesn't make the call easier to use, hence I think your change was
good to merge (and you already applied it as I see). 

Lennart

-- 
Lennart Poettering, Red Hat