Tracing changes of a variable's value? `nntp-marks-is-evil'

[Reiner Steib <reinersteib+gmane@imap.cc>]

Hi,

I have set the Gnus server variable `nntp-marks-is-evil' set to t
(default is nil).  Occasionally, e.g. when there are network problems,
after hitting `C-g', this variable changes to nil and I get errors
(see blow: [1]).

I don't know why the variable's value is changed.  Is the any way to
produce a backtrace when a variable changes?  I run Emacs under gdb,
if that is relevant.

[1]
--8<---------------cut here---------------start------------->8---
                  [Hitting `C-g'...]
Quit
                  [Hitting `g' in Gnus ...]
Checking new news...
Creating nntp marks directory ~/News/marks/localhost/foo.bar/
Updating marks for foo.bar...
Error reading nntp marks file ~/News/marks/localhost/foo.bar/ ((error
 IO error reading ~/News/marks/localhost/foo.bar/: Is a directory)).
 Continuing will use marks from .newsrc.eld.  Continue? (y or n)
Updating marks for foo.bar...done
Creating nntp marks directory ~/News/marks/localhost/foo.test/
Updating marks for foo.test...
Error reading nntp marks file ~/News/marks/localhost/foo.test/ ((error
 IO error reading ~/News/marks/localhost/foo.test/: Is a directory)).
 Continuing will use marks from .newsrc.eld.  Continue? (y or n)
Quit
                  [M-x rs-toggle-variable RET nntp-marks-is-evil RET ...]
`nntp-marks-is-evil' set to `t'
Checking new news...
                  [Everything fine again ...]
--8<---------------cut here---------------end--------------->8---

Bye, Reiner.
-- 
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      (o o)
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