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.
