From: Segher Boessenkool <segher@kernel.crashing.org>
To: "Alejandro Colomar (man-pages)" <alx.manpages@gmail.com>
Cc: Jonny Grant <jg@jguk.org>,
gcc-help@gcc.gnu.org, linux-man <linux-man@vger.kernel.org>,
Florian Weimer <fw@deneb.enyo.de>,
Michael Kerrisk <mtk.manpages@gmail.com>
Subject: Re: strlen
Date: Thu, 8 Jul 2021 18:49:29 -0500 [thread overview]
Message-ID: <20210708234929.GU1583@gate.crashing.org> (raw)
In-Reply-To: <feb6c15d-b242-83fc-c58d-2ebfbcd4f2bd@gmail.com>
On Thu, Jul 08, 2021 at 01:06:17PM +0200, Alejandro Colomar (man-pages) via Gcc-help wrote:
> On 7/8/21 12:07 PM, Jonny Grant wrote:
> >We can't guarantee safestrlen() won't be called with NULL. So because
> >strlen() itself doesn't check for NULL in C standard we'd need to call the
> >wrapper so that NULL can be checked for.
> >size_t __attribute__((optimize("O0"))) safestrlen(const char * s)
> >{
> > if (NULL == s) return 0;
> > else return strlen(s);
> >}
> That also allows differentiating a length of 0 (i.e., "") from an
> invalid string (i.e., NULL), by returning -1 for NULL.
It is incorrect to return any particular value for strlen(0); not 0, not
-1, not anything. Since there *is* no string, it doesn't have a length
either.
So instead of making some function for this, I recommend just writing
something like
bla = s ? strlen(s) : 0;
wherever you need it. If a function name isn't self-explanatory, and
even *cannot* be, your factoring is most likely not ideal. Code is
primarily there for humans to read, it should be optimised for that.
Segher
next prev parent reply other threads:[~2021-07-08 23:53 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-04 18:01 strlen Jonny Grant
2020-09-04 19:21 ` strlen Florian Weimer
2020-09-04 23:14 ` strlen Jonny Grant
2020-09-05 7:12 ` strlen Florian Weimer
2021-07-06 20:30 ` strlen Jonny Grant
2021-07-06 22:11 ` strlen Florian Weimer
2021-07-07 11:36 ` strlen Jonny Grant
2021-07-07 12:22 ` strlen Alejandro Colomar (man-pages)
2021-07-07 12:31 ` strlen Alejandro Colomar (man-pages)
2021-07-07 13:31 ` strlen Jonny Grant
2021-07-07 16:57 ` strlen Alejandro Colomar (man-pages)
2021-07-07 17:23 ` strlen Alejandro Colomar (man-pages)
2021-07-07 17:33 ` strlen Alejandro Colomar (man-pages)
2021-07-09 13:48 ` strlen Jonny Grant
2021-07-08 10:07 ` strlen Jonny Grant
2021-07-08 11:06 ` strlen Alejandro Colomar (man-pages)
2021-07-08 12:13 ` strlen Xi Ruoyao
2021-07-08 23:49 ` Segher Boessenkool [this message]
2021-07-09 13:54 ` strlen Jonny Grant
2021-07-09 14:17 ` strlen Alejandro Colomar (man-pages)
2021-07-09 16:11 ` strlen Xi Ruoyao
2021-07-10 1:00 ` strlen Segher Boessenkool
2021-07-09 10:50 ` strlen Jonny Grant
2021-07-09 11:27 ` strlen Alejandro Colomar (man-pages)
2021-07-09 11:43 ` strlen Alejandro Colomar (man-pages)
[not found] ` <1627912755.3783669.1625745946723@mail.yahoo.com>
[not found] ` <59a70222-a46f-1e65-c9db-6c9e577c8adc@126.com>
2021-07-09 17:26 ` strlen Martin Sebor
2021-07-09 20:19 ` strlen Alejandro Colomar (man-pages)
2021-07-09 20:44 ` strlen Jonny Grant
2021-07-10 18:37 ` strlen Alejandro Colomar (man-pages)
2021-07-10 20:49 ` strlen Jonny Grant
2021-07-10 21:36 ` strlen Alejandro Colomar (man-pages)
2021-07-12 21:16 ` strlen Jonny Grant
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
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210708234929.GU1583@gate.crashing.org \
--to=segher@kernel.crashing.org \
--cc=alx.manpages@gmail.com \
--cc=fw@deneb.enyo.de \
--cc=gcc-help@gcc.gnu.org \
--cc=jg@jguk.org \
--cc=linux-man@vger.kernel.org \
--cc=mtk.manpages@gmail.com \
/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.
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 NNTP newsgroup(s).