How to track changes to a variable?

[Juanma Barranquero]

I'm designing an elisp module that uses jit-lock to highlight text that
goes beyond the fill-column.

Supposedly, the module should somehow track (user) changes to the
variable fill-column. As there aren't change hooks for variables, what's
the best way to do it?

I've thought of:

 - Advising set-fill-column: not entirely right because programmatic
changes to the variable fill-column won't be detected, but that's OK
because my module is a user-level convenience. However, advising is not
recommended, I think.

 - Redefining set-fill-column, storing its original value and calling it
from my function: Ugly, and I don't know what is the gain wrt advising.

 - Installing a post-command-hook to check the value of fill-column: OK,
but too heavy-duty (I assume the user is not going to change the fill
column very often).

Any other option that I've overlooked?

Thanks,


                                                           /L/e/k/t/u