bug#39889: emacs-27 and master: unbalanced invocation of after-change-functions in cedet

[Alan Mackenzie]

Hello, Emacs.

In both the emacs-27 and master branches, in
.../lisp/cedet/srecode/insert.el, function srecode-insert-fcn,
after-change-functions is invoked without a matching invocation of
before-change-functions.  This violates the specified use of these hooks
described on the page "Change Hooks" in the Elisp manual.

CC Mode can recover from this scenario, though its recovery is slow (it
essentially runs the change hooks over the entire buffer).

It is not clear whether or not the syntax-ppss mechanism will recover
gracefully from this bug.

Any other uses of before-change-functions will probably suffer
corruption from this bug.

It looks like a good solution might well be to surround the pertinent
code with the combine-change-calls macro, at least for Emacs-27 onwards.
For the use of the cedet package in older emacsen, an explicit
invocation of before-change-functions needs adding.

-- 
Alan Mackenzie (Nuremberg, Germany).