The program which will be attached
demonstrates a case where,
when the -fstrict-aliasing optimization is turned on,
the result of the final one of 6 double-to-float conversions
does not get written to memory as it should.
According to valgrind (memory debugging tool), the target memory
gets left uninitialized.
The expected output and actual output are described in the program's comments.
I don't think I have done any illegal pointer aliasing in this program,
and the -Wstrict-aliasing=2 option doesn't warn of any such errors.
The problem occurs in g++ 4.1.2.
It does not occur in older versions I tried (4.0.2, 3.3.5)
nor at lower optimization levels.
The compiler version info, as shown by g++ -v, is:
Using built-in specs.
Target: x86_64-suse-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --libdir=/usr/lib64 --libexecdir=/usr/lib64
--with-gxx-include-dir=/usr/include/c++/4.1.2 --enable-languages=c,c++,fortran
--enable-shared --enable-threads=posix --disable-checking --with-system-zlib
--enable-__cxa_atexit --without-system-libunwind --enable-spp --disable-libssp
--enable-version-specific-runtime-libs --host=x86_64-suse-linux
Thread model: posix
gcc version 4.1.2
--
Summary: -fstrict-aliasing causes omission of double-to-float
conversion
Product: gcc
Version: 4.1.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: dhatch at ilm dot com
GCC build triplet: x86_64-suse-linux
GCC host triplet: x86_64-suse-linux
GCC target triplet: x86_64-suse-linux
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37679
