lsb(b) and msb(b) are undefined when b == 0. This can lead to subtle bugs, where the resulting code behaves differently on different configurations: - It can be the home grown software LSB/MSB - It can be the compiler generated software LSB/MSB (when using compiler intrinsics without the right compiler flags to allow compiler to use hardware LSB/MSB). Which of course depends on the compiler. - It can be hardware LSB/MSB generated by the compiler. - Not to mention that hardware LSB/MSB can return different value on different hardware when b == 0.