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From: "ebotcazou at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/100653] usage of scalar_storage_order produces incorrect result
Date: Wed, 26 May 2021 10:49:29 +0000 [thread overview]
Message-ID: <bug-100653-4-rqUaAG7F4B@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-100653-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100653
Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |INVALID
--- Comment #2 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> Attached test case produces invalid results with -O2, good with -O1.
See the manual:
Moreover, the use of type punning or aliasing to toggle the storage
order is not supported; that is to say, a given scalar object
cannot be accessed through distinct types that assign a different
storage order to it.
typedef struct tIp6Addr
{
unsigned int s6_addr32[4];
} tIp6Addr;
struct _tBeTimNetAddr
{
unsigned char isIPv4;
union
{
unsigned int addr;
tIp6Addr addr6;
} BB_MSG_ENDIANNESS u;
} BB_MSG_ENDIANNESS;
_tBeTimNetAddr.u.addr6.s6_addr32[0] is accessed in little-endian and
_tBeTimNetAddr.u.addr is accessed in big-endian, but they are the same scalar.
next prev parent reply other threads:[~2021-05-26 10:49 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-18 15:23 [Bug tree-optimization/100653] New: " jan.smets at nokia dot com
2021-05-19 1:14 ` [Bug tree-optimization/100653] " pinskia at gcc dot gnu.org
2021-05-26 10:49 ` ebotcazou at gcc dot gnu.org [this message]
2021-05-26 12:36 ` jan.smets at nokia dot com
2021-05-26 12:45 ` ebotcazou at gcc dot gnu.org
2021-05-26 13:04 ` ebotcazou at gcc dot gnu.org
2021-05-26 17:14 ` [Bug c/100653] " cvs-commit at gcc dot gnu.org
2021-05-26 22:26 ` cvs-commit at gcc dot gnu.org
2021-05-27 19:29 ` pinskia at gcc dot gnu.org
2021-06-15 15:49 ` george.thopas at gmail dot com
2021-06-15 16:42 ` ebotcazou at gcc dot gnu.org
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