From: "Alejandro Colomar (man-pages)" <alx.manpages@gmail.com>
To: наб <nabijaczleweli@nabijaczleweli.xyz>
Cc: linux-man@vger.kernel.org,
"Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>,
"G. Branden Robinson" <g.branden.robinson@gmail.com>
Subject: Re: [PATCH v2 4/5] alloca.3: remove GCC faffling from NOTES
Date: Sun, 19 Sep 2021 21:39:17 +0200 [thread overview]
Message-ID: <3cdc683a-b026-0e76-d039-738cb46142c7@gmail.com> (raw)
In-Reply-To: <20210917204530.3i2ctkt52gyfu7x7@tarta.nabijaczleweli.xyz>
Hi наб,
On 9/17/21 10:45 PM, наб wrote:
> On Wed, Sep 15, 2021 at 09:48:14PM +0200, Alejandro Colomar (man-pages) wrote:
>> On 9/14/21 2:41 PM, наб wrote:
>> [...]
>>> +is required, lest a symbol dependency be emitted.
>> Sorry that I'm not a native English speaker. I tried to learn what "lest"
>> means, but it's difficult to me, and I'm not sure I understand this line.
>> Could you maybe please reword it? :)
>
> I stand by the "lest" version because it gets less noodly,
> but rewritten as "in which case a symbol dependency will be emitted
> unless <alloca.h> is included", see updated scissor-patch below.
Hmm, the wording with 'lest' seems more precise, now that I learnt what
it means. I applied the first version. I also applied the rest of the
patches in this set (v1).
Thanks,
Alex
>
> And, well, neither am I, but that's hardly here or there.
>
> -- >8 --
> Chunks of glibc headers have no place in documenting an interface,
> and (__builtin_)alloca() is an intrinsic, not code; those days are,
> thankfully, long gone
>
> Also, clarify standards behaviour (and remove the (outdated!)
> list of cc(1) switches) regarding when alloca() is allowed to not be
> ODR-usable
>
> Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
> ---
> man3/alloca.3 | 52 +++++++++++++++------------------------------------
> 1 file changed, 15 insertions(+), 37 deletions(-)
>
> diff --git a/man3/alloca.3 b/man3/alloca.3
> index 20761b079..913cbe56a 100644
> --- a/man3/alloca.3
> +++ b/man3/alloca.3
> @@ -122,46 +122,24 @@ Do not attempt to
> .BR free (3)
> space allocated by
> .BR alloca ()!
> -.SS Notes on the GNU version
> -Normally,
> -.BR gcc (1)
> -translates calls to
> +.PP
> +By necessity,
> .BR alloca ()
> -with inlined code.
> -This is not done when either the
> -.IR "\-ansi" ,
> -.IR "\-std=c89" ,
> -.IR "\-std=c99" ,
> -or the
> -.IR "\-std=c11"
> -option is given
> -.BR and
> -the header
> -.I <alloca.h>
> -is not included.
> -Otherwise, (without an \-ansi or \-std=c* option) the glibc version of
> -.I <stdlib.h>
> -includes
> +is a compiler built-in, also known as
> +.BR __builtin_alloca ().
> +By default, modern compilers automatically translate all uses of
> +.BR alloca ()
> +into the built-in, but this is forbidden if standards conformance is requested
> +.RI ( "\-ansi" ,
> +.IR "\-std=c*" ),
> +in which case a symbol dependency will be emitted unless
> .I <alloca.h>
> -and that contains the lines:
> -.PP
> -.in +4n
> -.EX
> -#ifdef __GNUC__
> -#define alloca(size) __builtin_alloca (size)
> -#endif
> -.EE
> -.in
> +is included.
> .PP
> -with messy consequences if one has a private version of this function.
> -.PP
> -The fact that the code is inlined means that it is impossible
> -to take the address of this function, or to change its behavior
> -by linking with a different library.
> -.PP
> -The inlined code often consists of a single instruction adjusting
> -the stack pointer, and does not check for stack overflow.
> -Thus, there is no NULL error return.
> +The fact that
> +.BR alloca ()
> +is a built-in means it is impossible to take its address
> +or to change its behavior by linking with a different library.
> .SH BUGS
> Due to the nature of the stack, it is impossible to check if the allocation
> would overflow the space available, and, hence, neither is indicating an error.
>
--
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/
next prev parent reply other threads:[~2021-09-19 19:39 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-23 21:01 [PATCH 1/2] strdup.3: drop mention of "the GNU GCC suite" наб
2021-08-23 21:01 ` [PATCH 2/2] alloca.3: rewrite NOTES наб
2021-08-24 9:50 ` Michael Kerrisk (man-pages)
2021-08-24 10:04 ` G. Branden Robinson
2021-08-24 11:58 ` наб
2021-08-24 10:33 ` Alejandro Colomar (man-pages)
2021-08-24 11:18 ` Alejandro Colomar (man-pages)
2021-08-25 18:21 ` наб
2021-08-24 11:47 ` наб
2021-08-24 9:21 ` [PATCH 1/2] strdup.3: drop mention of "the GNU GCC suite" Michael Kerrisk (man-pages)
2021-08-24 10:28 ` наб
2021-08-24 10:40 ` Alejandro Colomar (man-pages)
2021-09-14 12:40 ` [PATCH v2 0/5] alloca(3) commentary re-write наб
2021-09-14 12:40 ` [PATCH v2 1/5] strdup.3: drop mention of "the GNU GCC suite" наб
2021-09-15 19:49 ` Alejandro Colomar (man-pages)
2021-09-14 12:41 ` [PATCH v2 2/5] alloca.3: clarify origins in CONFORMING TO наб
2021-09-15 19:49 ` Alejandro Colomar (man-pages)
2021-09-14 12:41 ` [PATCH v2 3/5] alloca.3: clarify reasoning for no error return in BUGS наб
2021-09-15 19:42 ` Alejandro Colomar (man-pages)
2021-09-17 20:35 ` наб
2021-09-14 12:41 ` [PATCH v2 4/5] alloca.3: remove GCC faffling from NOTES наб
2021-09-15 19:48 ` Alejandro Colomar (man-pages)
2021-09-17 20:45 ` наб
2021-09-19 19:39 ` Alejandro Colomar (man-pages) [this message]
2021-09-14 12:41 ` [PATCH v2 5/5] alloca.3: simplfy malloc(3) suite comparison, note VLAs наб
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=3cdc683a-b026-0e76-d039-738cb46142c7@gmail.com \
--to=alx.manpages@gmail.com \
--cc=g.branden.robinson@gmail.com \
--cc=linux-man@vger.kernel.org \
--cc=mtk.manpages@gmail.com \
--cc=nabijaczleweli@nabijaczleweli.xyz \
/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).