http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57484
--- Comment #3 from Charles L. Wilcox <zxClhzAApX1EdJwQANqrjLERmFeURQVy at cynd dot net> --- Daniel, Unfortunately, my initial machine, a laptop, decided to commit seppuku yesterday. Fortunately, the disk survived, I ported the code to another machine I have, and am still seeing similar results there. $ gcc -v Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.7/lto-wrapper Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Debian 4.7.2-5' --with-bugurl=file:///usr/share/doc/gcc-4.7/README.Bugs --enable-languages=c,c++,go,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.7 --enable-shared --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.7 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --enable-objc-gc --with-arch-32=i586 --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 4.7.2 (Debian 4.7.2-5) I updated my code to print out the full contents of the NaN values in hex. My machine produces the following output: $ g++ -Wall -Wextra test-signaling-nan.cpp -m32 $ ./a.out Signaling NaN for type "f" in hex is "7fe00000". Signaling NaN's signaling-bit status for type "f" is set to "true". Quiet NaN for type "f" in hex is "7fc00000". Quiet NaN's signaling-bit status for type "f" is set to "true". Signaling NaN for type "d" in hex is "7ffc000000000000". Signaling NaN's signaling-bit status for type "d" is set to "true". Quiet NaN for type "d" in hex is "7ff8000000000000". Quiet NaN's signaling-bit status for type "d" is set to "true". $ g++ -Wall -Wextra test-signaling-nan.cpp -m64 $ ./a.out Signaling NaN for type "f" in hex is "7fa00000". Signaling NaN's signaling-bit status for type "f" is set to "false". Quiet NaN for type "f" in hex is "7fc00000". Quiet NaN's signaling-bit status for type "f" is set to "true". Signaling NaN for type "d" in hex is "7ff4000000000000". Signaling NaN's signaling-bit status for type "d" is set to "false". Quiet NaN for type "d" in hex is "7ff8000000000000". Quiet NaN's signaling-bit status for type "d" is set to "true". The resulting values on 32-bit vs. 64-bit are different, and I believe the 64-bit values are the correct ones.
