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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/97493] generate wrong code with "-Os -fno-toplevel-reorder -frename-registers"
Date: Mon, 19 Oct 2020 14:06:06 +0000	[thread overview]
Message-ID: <bug-97493-4-oaLQ4heYJV@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-97493-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97493

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |jakub at gcc dot gnu.org
         Resolution|---                         |INVALID

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The testcase is invalid.  In standard C only one union member may be active at
a time, and while GCC as extension allows type puning through unions, the union
must be visible in the expressions accessing it, so taking addresses of the
union elts and dereferencing them through those pointers where the union is not
visible is UB.

  reply	other threads:[~2020-10-19 14:06 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-19 13:50 [Bug c/97493] New: " suochenyao at 163 dot com
2020-10-19 14:06 ` jakub at gcc dot gnu.org [this message]
2020-10-19 15:23 ` [Bug c/97493] " rguenth at gcc dot gnu.org
2020-10-19 15:39 ` jakub at gcc dot gnu.org
2020-10-20 12:59 ` suochenyao at 163 dot com
2020-10-20 12:59 ` suochenyao at 163 dot com
2020-10-30 15:28 ` suochenyao at 163 dot com

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