From: Paul Eggert <eggert@cs.ucla.edu>
To: Eli Zaretskii <eliz@gnu.org>
Cc: "Stephen J. Turnbull" <stephen@xemacs.org>,
dmantipov@yandex.ru, monnier@iro.umontreal.ca,
emacs-devel@gnu.org
Subject: Re: ptrdiff_t misuse
Date: Fri, 06 Jul 2012 07:56:48 -0700 [thread overview]
Message-ID: <4FF6FCB0.8080400@cs.ucla.edu> (raw)
In-Reply-To: <83bojt2lwm.fsf@gnu.org>
On 07/06/2012 04:01 AM, Eli Zaretskii wrote:
> It is easy enough to explain that EMACS_POS is used for Lisp integers
> that express buffer and string positions, and EMACS_INT for any other
> Lisp integer values.
But not every use of ptrdiff_t is for buffer and string positions.
Bitmap table sizes, for example. So we would need three types:
EMACS_INT for Lisp integer values
EMACS_POS for buffer and string positions
ptrdiff_t for other large memory-related numbers
and at that point, we'll need to teach Emacs hackers about
ptrdiff_t anyway.
An argument for EMACS_POS is that it clearly identifies an
integer as being used for a buffer or a string position, as
having some other ptrdiff_t-like use. But in that case shouldn't
we also distinguish between buffer positions and string positions?
And distinguish between character and byte counts, in both cases?
Something like this?
EMACS_INT for Lisp integer values
EMACS_BUFCPOS for buffer char positions
EMACS_BUFBPOS for buffer byte positions
EMACS_STRCPOS for string char positions
EMACS_STRBPOS for string byte positions
ptrdiff_t for other large memory-related numbers
This question answers itself, I think -- the extra complexity
isn't worth it, and we should stick with EMACS_INT and ptrdiff_t.
I think most competent C programmers know ptrdiff_t well enough.
They think of it being like size_t, but signed. Other GNU software
tends to prefer size_t, but the Emacs style is to prefer signed
integers and ptrdiff_t is the obvious alternative. I agree
that most C programs use 'int' for indexes, but that's because
they're small indexes. Emacs does this too, when indexes are
known to be sufficiently small.
next prev parent reply other threads:[~2012-07-06 14:56 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-29 13:20 (unknown) Eli Zaretskii
2012-06-29 14:18 ` ptrdiff_t misuse [was :Re: (empty)] Dmitry Antipov
2012-06-29 17:07 ` Stefan Monnier
2012-06-30 7:13 ` Paul Eggert
2012-06-30 7:27 ` Eli Zaretskii
2012-06-30 13:12 ` Paul Eggert
2012-06-30 14:23 ` Stefan Monnier
2012-06-30 12:07 ` Stefan Monnier
2012-06-30 13:14 ` Paul Eggert
2012-06-30 14:23 ` Stefan Monnier
2012-07-04 6:25 ` Paul Eggert
2012-07-04 16:39 ` Eli Zaretskii
2012-07-04 18:19 ` Paul Eggert
2012-07-05 16:31 ` Eli Zaretskii
2012-07-05 19:34 ` Eli Zaretskii
2012-07-06 0:08 ` Paul Eggert
2012-07-06 6:43 ` Eli Zaretskii
2012-07-06 7:32 ` Paul Eggert
2012-07-06 8:34 ` ptrdiff_t misuse Eli Zaretskii
2012-07-06 14:51 ` Paul Eggert
2012-07-06 21:30 ` Stefan Monnier
2012-07-06 21:33 ` Samuel Bronson
2012-07-07 10:59 ` Stefan Monnier
2012-07-07 15:34 ` Paul Eggert
2012-07-06 8:46 ` Eli Zaretskii
2012-07-06 10:19 ` Stephen J. Turnbull
2012-07-06 11:01 ` Eli Zaretskii
2012-07-06 12:02 ` Stephen J. Turnbull
2012-07-06 13:37 ` Eli Zaretskii
2012-07-06 16:25 ` Stephen J. Turnbull
2012-07-06 14:56 ` Paul Eggert [this message]
2012-07-06 15:43 ` Eli Zaretskii
2012-07-06 15:56 ` Paul Eggert
2012-07-06 16:00 ` Eli Zaretskii
2012-07-06 16:42 ` Dmitry Antipov
2012-07-06 17:39 ` Paul Eggert
2012-07-07 1:31 ` Chong Yidong
2012-06-29 18:54 ` ptrdiff_t misuse [was :Re: (empty)] Eli Zaretskii
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: https://www.gnu.org/software/emacs/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4FF6FCB0.8080400@cs.ucla.edu \
--to=eggert@cs.ucla.edu \
--cc=dmantipov@yandex.ru \
--cc=eliz@gnu.org \
--cc=emacs-devel@gnu.org \
--cc=monnier@iro.umontreal.ca \
--cc=stephen@xemacs.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.savannah.gnu.org/cgit/emacs.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).