[Bug 403744] Re: [PR42542] g++ -O3 produces incorrect results for less-than operator

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** Changed in: gcc
   Importance: Unknown => Medium

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Title:
  [PR42542] g++ -O3 produces incorrect results for less-than operator

Status in The GNU Compiler Collection:
  Fix Released
Status in “gcc-4.3” package in Ubuntu:
  Won't Fix
Status in “gcc-4.4” package in Ubuntu:
  Fix Released

Bug description:
  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

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