Public bug reported:
Binary package hint: g++-4.3
g++ appears to be (incorrectly) using a signed int comparison when -O3
optimization is enabled. Compiling with -O2 or lower produces the
correct output.
This problem was observed on Ubuntu 9.04 x86_64. The source code
(bug.cpp) is attached.
$ lsb_release -rd
Description: Ubuntu 9.04
Release: 9.04
$ uname -a
Linux rabota 2.6.28-13-generic #45-Ubuntu SMP Tue Jun 30 22:12:12 UTC 2009
x86_64 GNU/Linux
$ apt-cache policy g++-4.3
g++-4.3:
Installed: 4.3.3-5ubuntu4
Candidate: 4.3.3-5ubuntu4
Version table:
*** 4.3.3-5ubuntu4 0
500 http://us.archive.ubuntu.com jaunty/main Packages
100 /var/lib/dpkg/status
$ g++ --version
g++ (Ubuntu 4.3.3-5ubuntu4) 4.3.3
$ g++ -O2 bug.cpp && ./a.out
4264598888
$ g++ -O3 bug.cpp && ./a.out
1898580612
$ g++ -v -O3 bug.cpp
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.3.3-5ubuntu4'
--with-bugurl=file:///usr/share/doc/gcc-4.3/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --enable-nls --with-gxx-include-dir=/usr/include/c++/4.3
--program-suffix=-4.3 --enable-clocale=gnu --enable-libstdcxx-debug
--enable-objc-gc --enable-mpfr --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 4.3.3 (Ubuntu 4.3.3-5ubuntu4)
COLLECT_GCC_OPTIONS='-v' '-O3' '-shared-libgcc' '-mtune=generic'
/usr/lib/gcc/x86_64-linux-gnu/4.3.3/cc1plus -quiet -v -D_GNU_SOURCE bug.cpp
-D_FORTIFY_SOURCE=2 -quiet -dumpbase bug.cpp -mtune=generic -auxbase bug -O3
-version -fstack-protector -o /tmp/cc1tnMId.s
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory
"/usr/lib/gcc/x86_64-linux-gnu/4.3.3/../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/include/c++/4.3
/usr/include/c++/4.3/x86_64-linux-gnu
/usr/include/c++/4.3/backward
/usr/local/include
/usr/lib/gcc/x86_64-linux-gnu/4.3.3/include
/usr/lib/gcc/x86_64-linux-gnu/4.3.3/include-fixed
/usr/include/x86_64-linux-gnu
/usr/include
End of search list.
GNU C++ (Ubuntu 4.3.3-5ubuntu4) version 4.3.3 (x86_64-linux-gnu)
compiled by GNU C version 4.3.3, GMP version 4.2.4, MPFR version 2.4.0.
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: d9dd67dcc191271ac69fd2c05266cf9c
COLLECT_GCC_OPTIONS='-v' '-O3' '-shared-libgcc' '-mtune=generic'
as -V -Qy -o /tmp/ccZsdHhv.o /tmp/cc1tnMId.s
GNU assembler version 2.19.1 (x86_64-linux-gnu) using BFD version (GNU Binutils
for Ubuntu) 2.19.1
COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.3.3/:/usr/lib/gcc/x86_64-linux-gnu/4.3.3/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.3.3/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.3.3/:/usr/lib/gcc/x86_64-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.3.3/:/usr/lib/gcc/x86_64-linux-gnu/4.3.3/:/usr/lib/gcc/x86_64-linux-gnu/4.3.3/../../../../lib/:/lib/../lib/:/usr/lib/../lib/:/usr/lib/gcc/x86_64-linux-gnu/4.3.3/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-O3' '-shared-libgcc' '-mtune=generic'
/usr/lib/gcc/x86_64-linux-gnu/4.3.3/collect2 --eh-frame-hdr -m elf_x86_64
--hash-style=both -dynamic-linker /lib64/ld-linux-x86-64.so.2 -z relro
/usr/lib/gcc/x86_64-linux-gnu/4.3.3/../../../../lib/crt1.o
/usr/lib/gcc/x86_64-linux-gnu/4.3.3/../../../../lib/crti.o
/usr/lib/gcc/x86_64-linux-gnu/4.3.3/crtbegin.o
-L/usr/lib/gcc/x86_64-linux-gnu/4.3.3 -L/usr/lib/gcc/x86_64-linux-gnu/4.3.3
-L/usr/lib/gcc/x86_64-linux-gnu/4.3.3/../../../../lib -L/lib/../lib
-L/usr/lib/../lib -L/usr/lib/gcc/x86_64-linux-gnu/4.3.3/../../..
/tmp/ccZsdHhv.o -lstdc++ -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc
/usr/lib/gcc/x86_64-linux-gnu/4.3.3/crtend.o
/usr/lib/gcc/x86_64-linux-gnu/4.3.3/../../../../lib/crtn.o
** Affects: gcc-4.3 (Ubuntu)
Importance: Undecided
Status: New
** Tags: g++ optimization unsigned
--
g++ -O3 produces incorrect results for less-than operator
https://bugs.launchpad.net/bugs/403744
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