bug#30393: 24.4; cperl-mode: indentation failure

[Alan Mackenzie]

Hello, Eli.

On Mon, Mar 05, 2018 at 18:14:51 +0200, Eli Zaretskii wrote:
> > Date: Mon, 5 Mar 2018 08:42:55 +0000
> > From: Alan Mackenzie <acm@muc.de>
> > Cc: 30393@debbugs.gnu.org, Dmitry Gutov <dgutov@yandex.ru>,
> >     Noam Postavsky <npostavs@users.sourceforge.net>

> > Existing C functions have been modified as follows:
> >   o - signal_after_change.
> >     * - Regardless of the settings of the change hooks,
> >       syntax-ppss-flush-cache will be called for an actual textual
> >       change.
> >   o - Fset_syntax_table.
> >     * - If the new table is literally different from the old,
> >       syntax-ppss-flush-cache will be called with an argument of -1.
> >   o - Fmodify_syntax_entry.
> >     * - If the new entry is literally different from the old one,
> >       syntax-ppss-flush-cache will be called with an argument of -1.
> >   o - init_syntax_once and syms_of_syntax.
> >     * - Administrative amendments.
> >   o - set_properties, add_properties, remove_properties.  If a
> >     syntax-table property set or removed, whether directly or via a
> >     category property, potentially alters the parsing of literals,
> >     syntax-ppss-flush-cache will be called.

> Any reason why you introduce 2 new primitives that no Lisp code uses?

least-literal-difference-between-syntax-tables and
syntax-tables-literally-different-p?  They're for helping with
debugging.  Syntax tables, like char tables in general, are awkward
unwieldy beasts.  Sooner or later, somebody debugging is going to want
to compare two syntax tables which aren't behaving as she expects they
should.  Those primitives (which, yes, will need documenting) were cheap
and easy to write, but would be awkward and unwieldy to write as
one-offs in Lisp.

> In any case, this needs documentation changes if and when it's agreed
> upon.

Yes, but less documentation that would be needed without it.
Introducing the syntax-ppss mechanism into syntax primitives broke them,
since its cache invalidation is imperfect.  With my patch, aside from
any bugs in it, those primitives are less broken, hence less
documentation of the breakage is needed.

> Thanks.

-- 
Alan Mackenzie (Nuremberg, Germany).