public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "agamous at bgcpartners dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/47603] New: Optimization level O2 nad O3 produces different output from level O1 and O0
Date: Thu, 03 Feb 2011 21:19:00 -0000 [thread overview]
Message-ID: <bug-47603-4@http.gcc.gnu.org/bugzilla/> (raw)
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47603
Summary: Optimization level O2 nad O3 produces different output
from level O1 and O0
Product: gcc
Version: 4.4.3
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: agamous@bgcpartners.com
CC: agamous@bgcpartners.com
Source code to compile
#include <stdio.h>
int main()
{
int i32 =0x12345678;
short *t = (short *)&i32;
t[0] = 0xaa;
t[1] = 0xbb;
printf("i32 = %lx\n", i32);
return 0;
}
We tried both gcc and g++ with the same compilation options and the same
result.
Compilation line (optimization O3 or O2)
gcc -O3 -o foo foo.c
run as ./foo
output i32 = 12345678
If compiles with O1 or O0
gcc -O0 -o foo foo.c
output i32 = bb00aa
GCC version
> * the exact version of GCC, as shown by "gcc -v";
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
4.4.3-4ubuntu5' --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr
--enable-shared --enable-multiarch --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4
--program-suffix=-4.4 --enable-nls --enable-clocale=gnu
--enable-libstdcxx-debug --enable-plugin --enable-objc-gc
--disable-werror --with-arch-32=i486 --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5)
CPU
Intel(R) Core(TM)2 Duo CPU E8400 @ 3.00GHz
system type
uname -a displays the following
Linux 2.6.32-24-generic #39-Ubuntu SMP Wed Jul 28 05:14:15 UTC 2010
x86_64 GNU/Linux
next reply other threads:[~2011-02-03 21:19 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-03 21:19 agamous at bgcpartners dot com [this message]
2011-02-03 21:27 ` [Bug c++/47603] " pinskia at gcc dot gnu.org
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=bug-47603-4@http.gcc.gnu.org/bugzilla/ \
--to=gcc-bugzilla@gcc.gnu.org \
--cc=gcc-bugs@gcc.gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).