From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 12880 invoked by alias); 3 Feb 2011 21:19:23 -0000 Received: (qmail 12632 invoked by uid 22791); 3 Feb 2011 21:19:22 -0000 X-SWARE-Spam-Status: No, hits=-2.5 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00,TW_BJ,TW_CX,TW_DC,TW_GX X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 03 Feb 2011 21:19:18 +0000 From: "agamous at bgcpartners dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/47603] New: Optimization level O2 nad O3 produces different output from level O1 and O0 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c++ X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: agamous at bgcpartners dot com X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Changed-Fields: Message-ID: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Date: Thu, 03 Feb 2011 21:19:00 -0000 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2011-02/txt/msg00564.txt.bz2 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 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