watching for variable assignment

[Eric Abrahamsen <eric@ericabrahamsen.net>]

I've been fighting gnus recently over mail splitting, trying to keep the
variable nnimap-split-fancy set to my preferred value -- as I use gnus,
some other part of the code keeps setting it to "nil" and messing up my
splits.

I'd really like to know what's doing that, so I'm trying to somehow
trigger a message or a backtrace whenever that variable's value changes.
I tried advising "set" (thinking that set was the most fundamental
function for variable assignment), but that doesn't seem to get called.
I advised "setq", but that gave me a recursion exception: defadvice
probably uses setq itself.

What are my other options? How do I figure out who keeps blanking this
variable out?

Thanks,
Eric

Using GNU Emacs 24.3.1. Hmm, maybe if I tried emacs from git, and the
new add-function stuff...