Re: Discrepancy in definition/use of match-data?

[Richard Stallman]

      In general, even a simple variable
    reference can call arbitrary Lisp code in XEmacs (because of magic
    Mule handlers) and most likely GNU Emacs (because those handlers were
    introduced for GNU Emacs compatibility).

I have never heard of "magic Mule handlers", and I am pretty sure there
is nothing like this in Emacs.  If we had them, we would make them save
and restore the match data.

    On the other hand, pretty much any time any Lisp code intervenes
    between the return of the matching function and entry to the match
    data access there is an opportunity for a hook or handler to be
    called.

That is rather an exaggeration.  Most of the Lisp functions described
in the manual cannot call any hook.  Asynchronous activities only happen
inside functions that can wait, which means, only certain primitives.
Likewise for file name handlers.  And these normally save the match
data anyway.