From: Stefan Monnier <monnier@iro.umontreal.ca>
To: emacs-devel@gnu.org
Subject: Re: Simplify internal_catch()
Date: Tue, 27 Dec 2016 21:50:21 -0500 [thread overview]
Message-ID: <jwveg0s7oud.fsf-monnier+gmane.emacs.devel@gnu.org> (raw)
In-Reply-To: 87k2aku8bk.fsf@gmail.com
> --- a/src/eval.c
> +++ b/src/eval.c
> @@ -458,7 +458,11 @@ usage: (progn BODY...) */)
> void
> prog_ignore (Lisp_Object body)
> {
> - Fprogn (body);
> + while (CONSP (body))
> + {
> + eval_sub (XCAR (body));
> + body = XCDR (body);
> + }
> }
Why bother? This is not performance-critical code, so the most
important criterion is to make the code clear and reduce redundancy.
> THE DIFF FOR THIS PATCH is in the attachments.
Both patches are identical, right?
> - struct handler *c = push_handler (tag, CATCHER);
> + struct handler *c;
> + Lisp_Object val;
> +
> + c = push_handler (tag, CATCHER);
Why place the declaration of `val` between the two? I always strongly prefer
initializing a var directly in its declaration so that you simply cannot
refer to it in an uninitialized state. Even more so for a variable
which is never modified afterwards.
> if (! sys_setjmp (c->jmp))
> - {
> - Lisp_Object val = func (arg);
> - clobbered_eassert (handlerlist == c);
> - handlerlist = handlerlist->next;
> - return val;
> - }
> + /* Call FUNC. */
> + val = func (arg);
> else
> - { /* Throw works by a longjmp that comes right here. */
> - Lisp_Object val = handlerlist->val;
> - clobbered_eassert (handlerlist == c);
> - handlerlist = handlerlist->next;
> - return val;
> - }
> + /* Throw works by a longjmp that comes right here. */
> + val = handlerlist->val;
> + clobbered_eassert (handlerlist == c);
> + handlerlist = handlerlist->next;
> + return val;
Right: sharing the tail is a good idea, thanks.
Stefan
next prev parent reply other threads:[~2016-12-28 2:50 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-28 1:54 Simplify internal_catch() Chris Gregory
2016-12-28 2:50 ` Stefan Monnier [this message]
-- strict thread matches above, loose matches on Subject: below --
2016-12-28 6:33 Chris Gregory
2016-12-28 8:48 ` Andreas Schwab
2016-12-28 16:45 ` Stefan Monnier
2016-12-28 19:24 ` Paul Eggert
2016-12-28 19:28 ` Stefan Monnier
2016-12-31 21:29 ` Paul Eggert
2016-12-28 7:34 [no subject] Chris Gregory
2016-12-28 7:42 ` Simplify internal_catch () Paul Eggert
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