From: Federico Tedin <federicotedin@gmail.com>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: emacs-devel@gnu.org
Subject: Re: Patch to remove a bit of duplicated code in eval.c
Date: Fri, 17 Sep 2021 22:27:47 +0200 [thread overview]
Message-ID: <CAA8GjPkV=qUbv7whTiJHbqdPt1Ymgm36a4i7Vy2EX-yRrheAWQ@mail.gmail.com> (raw)
In-Reply-To: <jwvk0jfgnmd.fsf-monnier+emacs@gnu.org>
(Apologies if there's any strange formatting, can't find this email on
Gnus and had to reply with the web client)
On Fri, Sep 17, 2021 at 7:11 PM Stefan Monnier <monnier@iro.umontreal.ca> wrote:
>
> > @@ -3081,11 +2978,52 @@ DEFUN ("funcall", Ffuncall, Sfuncall, 1, MANY, 0,
> > }
> >
> >
> > +static Lisp_Object
> > +apply_subr (struct Lisp_Subr *subr, Lisp_Object args, ptrdiff_t count)
> > +{
>
> I think this definition deserves a comment explaining at least what is
> `count` (the other two are fairly self-explanatory, but not that one).
Good point.
> > + Lisp_Object *arg_vector;
> > + Lisp_Object tem;
> > + USE_SAFE_ALLOCA;
> > +
> > + ptrdiff_t numargs = list_length (args);
> > +
> > + if (subr->max_args != UNEVALLED)
> > + {
> > + Lisp_Object args_left = args;
> > + SAFE_ALLOCA_LISP (arg_vector, numargs);
> > +
> > + for (ptrdiff_t i = 0; i < numargs; i++)
> > + {
> > + tem = Fcar (args_left);
> > + args_left = Fcdr(args_left);
> > + tem = eval_sub(tem);
>
> [ Be careful to remember to put a space before the open parens. ]
Will do!
> > Lisp_Object
> > -funcall_subr (struct Lisp_Subr *subr, ptrdiff_t numargs, Lisp_Object *args)
> > +funcall_subr (struct Lisp_Subr *subr, ptrdiff_t numargs, Lisp_Object *args, bool unevalled_ok)
> > {
>
> I'm not very happy with this.
> Everywhere else in Emacs, the name "funcall" means we're calling
> a *function* and not a special form. I think we'd be better off keeping
> `funcall_subr` unchanged and use "something else" when `+apply_subr`
> needs to handle a special form (aka `UNEVALLED`).
>
> That will also make it obvious that the patch does not slow down
> execution of bytecode at all (which does use `funcall_subr` but
> not `eval_sub`).
That is a great idea. I was not very satisfied with the change to
'funcall_subr' either. Fitting the change entirely in 'apply_subr'
should not be too difficult.
> > My concerns now are:
> > 1) Could I have broken anything without realizing it, since this is such
> > a central function in Lisp code evaluation? Everything seems to be
> > compiling fine (without warnings) and so far I haven't had any crashes.
>
> I haven't looked in enough details to be sure, but in principle it
> should be OK since it re-uses the well-tested `funcall_subr` code.
>
> > 2) I removed a comment that made reference to Bug#21245, but it seems
> > like it makes sense since the variable it refers to is no longer needed.
>
> That removal looks good, thanks.
>
> > 3) Have I maybe made Emacs slower by always using SAFE_ALLOCA_LISP for
> > the subroutine arguments (instead of only for 'max_args=MANY')?
>
> It might slightly slow down execution of interpreted code, but
> interpreted code should not be performance critical (after all, if
> speed matters, the answer is to byte-compile the code). You can try and
> measure the slowdown in the following way:
>
> rm src/*.pdmp lisp/**/*.elc
> (cd src; make bootstrap-emacs.pdmp)
> rm lisp/**/*.elc
> (cd lisp; time make emacs-lisp/macroexp.elc)
>
> The important part is to time the `make emacs-lisp/macroexp.elc`.
> The three lines before it only serve to get to a state where we have
> a working Emacs executable with no bytecode at all (so the compilation
> of `macroexp.el` takes a long while because all the code is
> interpreted).
Thanks for the tip on measuring execution speed. I think I might be
able to undo this particular change though, since I didn't realize
that if max_args!=MANY,
then there's the possibility of just using a Lisp_Object args[8],
which is what the code that I removed did (I commented this in my
reply to Eli). So this change
was unnecessary.
Appreciate the feedback!
prev parent reply other threads:[~2021-09-17 20:27 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-16 21:49 Patch to remove a bit of duplicated code in eval.c Federico Tedin
2021-09-17 7:29 ` Eli Zaretskii
2021-09-17 20:08 ` Federico Tedin
2021-09-17 17:11 ` Stefan Monnier
2021-09-17 20:27 ` Federico Tedin [this message]
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