[cups.development] Deleting printers that have no backend

[Matt Anderson]

Jim Fehlig wrote:
> I have encountered configurations where it is possible to have printers 
> installed with no corresponding backend to communicate with the target 
> device.  Details can be provided at how I arrived at such a 
> configuration, but don't believe it is terribly relevant.
> 
> I would like to get the community's thoughts on providing a patch that 
> would delete printers for which there is no corresponding backend to 
> service the queue.  I have looked into deleting the printer when a job 
> is processed and we find that exec()ing the backend fails with ENOENT.  
> Such a patch appears to be fairly simple but wanted to get some feedback 
> before creating it.

I'd be concerned about this functionality if it became the default 
behavior or was somehow not overrideable.  In an MLS environment where 
cups was serving as a labeled printing server this feature could lead to 
undesired behavior since a printer set at secret might get an ENOENT 
when it tried to open /dev/lp0 which was at that time set to topsecret.

-matt