[Bug c/43637] New: [4.4/4.5 regression] miscompilation in strict-aliasing optimization

["jengelh at medozas dot de" <gcc-bugzilla at gcc dot gnu dot org>]

I have here a testcase where -fstrict-aliasing seems to miscompiles the code.

$ gcc-4.4 tc.c -o tc && ./tc
$ gcc-4.4 tc.c -o tc -O1 && ./tc
$ gcc-4.4 tc.c -o tc -O1 -fstrict-aliasing && ./tc
Segmentation fault
$ gcc-4.4 tc.c -o tc -O1 -fstrict-aliasing -DOK && ./tc
0xaf8bea20

This also happens with the gcc-4.5 snapshot.

> gcc-4.4 -v
Using built-in specs.
Target: i586-suse-linux
Configured with: ../configure --prefix=/usr --infodir=/usr/share/info
--mandir=/usr/share/man --libdir=/usr/lib --libexecdir=/usr/lib
--enable-languages=c,c++,objc,fortran,obj-c++,java,ada
--enable-checking=release --with-gxx-include-dir=/usr/include/c++/4.4
--enable-ssp --disable-libssp --with-bugurl=http://bugs.opensuse.org/
--with-pkgversion='SUSE Linux' --disable-libgcj --disable-libmudflap
--with-slibdir=/lib --with-system-zlib --enable-__cxa_atexit
--enable-libstdcxx-allocator=new --disable-libstdcxx-pch
--enable-version-specific-runtime-libs --program-suffix=-4.4
--enable-linux-futex --without-system-libunwind --with-arch-32=i586
--with-tune=generic --build=i586-suse-linux
Thread model: posix
gcc version 4.4.1 [gcc-4_4-branch revision 150839] (SUSE Linux) 

> gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/i586-suse-linux/4.5/lto-wrapper
Target: i586-suse-linux
Configured with: ../configure --prefix=/usr --infodir=/usr/share/info
--mandir=/usr/share/man --libdir=/usr/lib --libexecdir=/usr/lib
--enable-languages=c,c++,objc,fortran,obj-c++,java,ada
--enable-checking=release --with-gxx-include-dir=/usr/include/c++/4.5
--enable-ssp --disable-libssp --disable-plugin
--with-bugurl=http://bugs.opensuse.org/ --with-pkgversion='SUSE Linux'
--disable-libgcj --disable-libmudflap --with-slibdir=/lib --with-system-zlib
--enable-__cxa_atexit --enable-libstdcxx-allocator=new --disable-libstdcxx-pch
--enable-version-specific-runtime-libs --program-suffix=-4.5
--enable-linux-futex --without-system-libunwind --enable-gold
--with-plugin-ld=/usr/bin/gold --with-arch-32=i586 --with-tune=generic
--build=i586-suse-linux
Thread model: posix
gcc version 4.5.0 20100331 (experimental) [trunk revision 157870] (SUSE Linux)


-- 
           Summary: [4.4/4.5 regression] miscompilation in strict-aliasing
                    optimization
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jengelh at medozas dot de
 GCC build triplet: i586-suse-linux-gnu
  GCC host triplet: i586-suse-linux-gnu
GCC target triplet: i586-suse-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43637