From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 28193 invoked by alias); 10 Jul 2014 09:52:12 -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 Received: (qmail 28085 invoked by uid 48); 10 Jul 2014 09:52:03 -0000 From: "theemathas at hotmail dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/61769] New: const reference value is changed to random by a range-for loop Date: Thu, 10 Jul 2014 09:52:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c++ X-Bugzilla-Version: 4.8.2 X-Bugzilla-Keywords: X-Bugzilla-Severity: major X-Bugzilla-Who: theemathas at hotmail 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-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status bug_severity priority component assigned_to reporter Message-ID: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-SW-Source: 2014-07/txt/msg00618.txt.bz2 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61769 Bug ID: 61769 Summary: const reference value is changed to random by a range-for loop Product: gcc Version: 4.8.2 Status: UNCONFIRMED Severity: major Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: theemathas at hotmail dot com I previously thought that the g++ compiler should not contain bugs when compiling valid code without using very strange tricks. However, the bug I found can be generated using a relatively simple program. A const reference is assigned to be the result of a certain function, and the value is somehow changed by a for-each loop (that is supposedly useless) to a random value. The non-preprocessed source code I have is very short (18 actual code lines, counted by code::blocks). It should output 55 (a random literal hard-coded into the program) It outputs random values, changing on each run. -----start output of "g++ -v"----- Using built-in specs. COLLECT_GCC=g++ COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.8/lto-wrapper Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.8.2-19ubuntu1' --with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs --enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.8 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-libmudflap --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --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 4.8.2 (Ubuntu 4.8.2-19ubuntu1) -----end output of "g++ -v"----- No warnings or errors when compiling program with "g++ -std=c++11 -pedantic -Wall -Wextra main.cpp". The bug disappears after adding one of the following flags: "-O1", "-O2", "-O3" The shortest command line that still produces the bug is "g++ -std=c++11 main.cpp" The "main.ii" file created using the command "g++ -save-temps -std=c++11 -pedantic -Wall -Wextra main.cpp" is attached Thank you.