From: Stephan Bergmann <sbergman@redhat.com>
To: libc-alpha@sourceware.org
Cc: Vincent Lefevre <vincent@vinc17.net>,
Paul Eggert <eggert@cs.ucla.edu>,
Simon Chopin <simon.chopin@canonical.com>
Subject: Re: UB status of snprintf on invalid ptr+size combination?
Date: Thu, 16 Mar 2023 11:29:31 +0100 [thread overview]
Message-ID: <92810b6e-e7e6-6ffd-d33a-067b9f300059@redhat.com> (raw)
In-Reply-To: <20230315123949.GC73312@zira.vinc17.org>
On 15/03/2023 13:39, Vincent Lefevre wrote:
> No, it is not obvious. If the C standard does not say that this is
> the size of the array, then it does not have to be the size of the
> array. The C standard just says:
>
> Otherwise, output characters beyond the n-1st are discarded rather
> than being written to the array, and a null character is written at
> the end of the characters actually written into the array.
But in 7.1.4 "Use of library functions" the standard also says
> If a function argument is described as being an array, the pointer passed to the function shall
> have a value such that all address computations and accesses to objects (that would be valid if
> the pointer did point to the first element of such an array) are valid.
which could be construed as meaning that the n-1st array element must
always be accessible, even if a given invocation is known to always
generate less then n output characters.
next prev parent reply other threads:[~2023-03-16 10:29 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
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 [this message]
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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