it's not uncommon for runtimes to use always-zero bits from aligned pointers or bits above 48 (unused in most current 64bit CPUs) to store flags today. you don'

it's not uncommon for runtimes to use always-zero bits from aligned pointers or bits above 48 (unused in most current 64bit CPUs) to store flags today. you don't need special 'bit-addressing' to do it. byte addressing works just fine.