[systemd-devel] [PATCH] core: don't allow enabling if unit is masked

[Zbigniew Jędrzejewski-Szmek]

On Wed, Oct 08, 2014 at 09:28:39PM +0200, Lennart Poettering wrote:
> On Wed, 08.10.14 17:24, Zbigniew Jędrzejewski-Szmek (zbyszek at in.waw.pl) wrote:
> 
> > > > I think that the best way to handle this would be to
> > > > use a temporary structure like
> > > >    { char *unit_name; char *error_message; int code}
> > > > and use this to pass the information about the error from the lower
> > > > to the upper levels. But maybe I'm overcomplicating things.
> > > 
> > > Hmm, maybe a simply solution would be to convert EADDRNOTAVAIL into a
> > > proper sd_bus_error on the calling side, that shouldn't be too
> > > difficult.
> > 
> > You can convert to an error, sure, but it is really nice to deliver
> > a specific message like "Unit boo.service is masked", instead of
> > "A unit is masked".
> 
> Well, true, but then again, it's not thaaaaaat much worse...
Yeah, I guess now its time to do a proof-of-concept implementation to
see how it works in practice.
 
> > > > A related thing: there's a mapping bus-error <-> errno implemented,
> > > > but it only works for the errors defined in the library itself. It
> > > > would be nice to extend this mapping to the "user" defined errors,
> > > > e.g. in core/.  Would you be amenable to adding a mechianism to
> > > > register additional mappings like bus-error-mapping.gperf so that they
> > > > are used by the library?
> > > 
> > > Maybe have internal versions of the conversion calls that allow
> > > passing in an additional table?
> > That is not as convenient. E.g. sd_bus_error_set
> > internally calls bus_error_name_to_errno. Currently, this always
> > returns EIO for errors unknown to the library, and then the caller
> > does it own lookup (e.g. looking at transaction_add_job_and_dependencies()).
> 
> What precisely are you proposing instead?

typedef const name_error_mapping*
(*bus_error_mapping_lookup_t) (const char *str, size_t len);

int bus_error_add_mapping(bus_error_mapping_lookup_t mapping);

This could be used to register a custom function similar to our
bus_error_mapping_lookup(). It would get stored in a global table (of
fixed size?), and bus_error_mapping_lookup would be the first slot in
this table and the calls to bus_error_mapping_lookup would be
replace by a function which iterates over this table and
returns the first successful lookup.

Zbyszek