Catching errors from scm_run_hook

[Greg Badros <gjb@cs.washington.edu>]

What is the right, supported way to catch errors when invoking
scm_run_hook?  E.g., in Scwm, we do not want an error in a user's hook
to exit the window manager, but instead want to run scwm_handle_error.
In scwm's callbacks.c, we've a bunch of code that does safe (catching)
applications from new dynamic roots.  It seems like there should be a
better way to do this than make each application roll its own.  Is there?

Ideally, something like:

scm_catching_run_hook(scwm_handle_error, motion_hook, SCM_EOL);

would just DTRT.  (Maybe doing the right thing also involves starting
from a new dynamic root...)

Thanks!

Greg