bug#24923: 25.1; Lisp watchpoints

[npostavs]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: npostavs@users.sourceforge.net
>> Cc: 24923@debbugs.gnu.org
>> Date: Fri, 11 Nov 2016 23:34:33 -0500
>> 
>> >> +          (_ (format "watchpoint triggered %S" (cdr args))))
>> >
>> > Can you give a couple of examples of this, with %S shown explicitly?
>> > I'm not sure whether the result will be self-explanatory.
>> 
>> You mean examples of this this clause being used?  It was meant more as
>> a catchall in case some watch types were missed by the previous clauses.
>> It shouldn't really ever happen unless the debugger and watchpoint code
>> get out of sync.  Do you think it would be better to just signal an
>> error?  (although would signalling an error while the debugger is
>> invoked cause trouble?)
>
> Either signal an error, or include something like "(please submit a
> bug report)" in the text.

Here is the updated patch, created with -b.  I went with a call to
`error'.  And actually, I had missed a couple of watchpoint types.

v5-b-0001-Add-lisp-watchpoints.patch
Description: patch

v5-b-0002-Add-function-to-trigger-debugger-on-variable-writ.patch
Description: patch

v5-b-0003-Ensure-redisplay-using-variable-watcher.patch
Description: patch

v5-b-0004-Add-tests-for-watchpoints.patch
Description: patch

v5-b-0005-etc-NEWS-Add-entry-for-watchpoints.patch
Description: patch

For the manual, do you think I should document just the debugging
commands, or should there additionally be a section in the "Variables"
chapter about the watchpoint mechanism?