From: Michael Hudson-Doyle <michael.hudson@canonical.com>
To: Andreas Schwab <schwab@suse.de>
Cc: Paul Eggert <eggert@cs.ucla.edu>,
Simon Chopin <simon.chopin@canonical.com>,
libc-alpha@sourceware.org
Subject: Re: UB status of snprintf on invalid ptr+size combination?
Date: Thu, 16 Mar 2023 07:34:31 +1300 [thread overview]
Message-ID: <CAJ8wqtdikMs5Pb5+S=VWNL39Yyoz6PjJDdhZCY0iO86AesqBUg@mail.gmail.com> (raw)
In-Reply-To: <mvmy1nyz7w7.fsf@suse.de>
[-- Attachment #1: Type: text/plain, Size: 1210 bytes --]
On Wed, 15 Mar 2023 at 22:22, Andreas Schwab via Libc-alpha <
libc-alpha@sourceware.org> wrote:
> On Mär 14 2023, Paul Eggert wrote:
>
> > For example, it's valid for snprintf to be implemented this way:
> >
> > int
> > snprintf (char *buf, size_t size, char const *fmt, ...)
> > {
> > char *buf_limit = buf + size;
> > ...
> > }
> >
> > even though this would have undefined behavior if BUF points to a
> > character array smaller than SIZE.
>
> Since it is part of the implementation it is irrelevant from the POV of
> the standard. The implementation does not have to abide to the C
> standard, as long as it properly implements the interface constraints.
>
> What matters is the wording of the standard. The POSIX standard is more
> explicit here: "with the addition of the n argument which states the
> size of the buffer referred to by s." Probably the C standard should be
> clarified.
>
Ah that's interesting that POSIX is clearer here, thanks for pointing that
out. I can feel more confident declaring the affected code broken now :-)
Is anyone here close enough to the C standards process to push getting this
clarified there?
Cheers,
mwh
next prev parent reply other threads:[~2023-03-15 18:34 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-14 19:47 Simon Chopin
2023-03-14 21:39 ` Paul Eggert
2023-03-15 9:22 ` Andreas Schwab
2023-03-15 15:54 ` Siddhesh Poyarekar
2023-03-15 18:34 ` Michael Hudson-Doyle [this message]
2023-03-19 14:45 ` manfred
2023-03-19 23:07 ` Vincent Lefevre
2023-03-20 12:05 ` Siddhesh Poyarekar
2023-03-20 12:17 ` Alejandro Colomar
2023-03-20 12:29 ` Siddhesh Poyarekar
2023-03-20 13:36 ` Vincent Lefevre
2023-03-20 13:50 ` Vincent Lefevre
2023-03-20 16:56 ` Siddhesh Poyarekar
2023-03-20 17:36 ` Vincent Lefevre
2023-03-20 15:09 ` Vincent Lefevre
2023-03-20 16:15 ` Alejandro Colomar
2023-03-20 16:33 ` Vincent Lefevre
2023-03-20 17:00 ` Vincent Lefevre
2023-03-20 17:31 ` Siddhesh Poyarekar
2023-03-20 17:45 ` Vincent Lefevre
2023-03-15 12:39 ` Vincent Lefevre
2023-03-16 10:29 ` Stephan Bergmann
2023-03-18 2:07 ` Vincent Lefevre
2023-03-18 2:30 ` Alejandro Colomar
2023-03-18 10:58 ` Vincent Lefevre
2023-03-18 15:01 ` Andreas Schwab
2023-03-19 22:48 ` Vincent Lefevre
2023-03-19 23:24 ` Andreas Schwab
2023-03-20 4:10 ` Vincent Lefevre
2023-03-20 9:19 ` Andreas Schwab
2023-03-20 10:42 ` Vincent Lefevre
2023-03-20 10:44 ` Andreas Schwab
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