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From: "kees at outflux dot net" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/101832] __builtin_object_size(P->M, 1) where M ends with a flex-array behaves like sizeof()
Date: Mon, 09 Aug 2021 18:07:19 +0000	[thread overview]
Message-ID: <bug-101832-4-80KOUlvLI5@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-101832-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101832

--- Comment #5 from Kees Cook <kees at outflux dot net> ---
Perhaps the best question to ask is "given an arbitrary argument, how can code
detect the remaining bytes of a member, including if the member contains a
flexible array?"

Because right now, this does not work:

#define __bytes_until_end_of_member(p) __builtin_object_size(p, 1)

since this gives different answers, depending on the level of dereference:

__bytes_until_end_of_member(wrap) == -1
__bytes_until_end_of_member(&wrap->msg) == 16
__bytes_until_end_of_member(&wrap->msg.nlmsg_content) == -1

How can "wrap->msg" be 16 if "wrap" and "warp->msg.nlmsg_content" are -1?

  parent reply	other threads:[~2021-08-09 18:07 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-09 17:01 [Bug c/101832] New: " kees at outflux dot net
2021-08-09 17:10 ` [Bug c/101832] " kees at outflux dot net
2021-08-09 17:10 ` kees at outflux dot net
2021-08-09 17:16 ` jakub at gcc dot gnu.org
2021-08-09 17:50 ` kees at outflux dot net
2021-08-09 18:07 ` kees at outflux dot net [this message]
2022-08-25 20:11 ` qinzhao at gcc dot gnu.org
2023-01-20 16:46 ` qinzhao at gcc dot gnu.org
2023-01-25 21:54 ` qinzhao at gcc dot gnu.org
2023-01-26 17:00 ` qinzhao at gcc dot gnu.org
2023-01-27 16:04 ` qinzhao at gcc dot gnu.org
2023-06-21 19:40 ` [Bug tree-optimization/101832] " qinzhao at gcc dot gnu.org
2023-06-30 18:24 ` cvs-commit at gcc dot gnu.org
2023-07-19 19:27 ` qinzhao at gcc dot gnu.org
2023-07-19 19:28 ` qinzhao at gcc dot gnu.org
2023-07-19 20:03 ` qinzhao at gcc dot gnu.org

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