In the article he states "[for Copying] Conservative GC is unable to determine the difference between pointer and integer values. If an integer value was overwritten the result would be disastrous. It is likely that the result of 1+1 would change occasionally."
However reading through the RHG, it is shown that Ruby allocates memory for objects in 20 byte blocks and that this results in all pointers therefore being multiples of four. This is handy as it allows the direct usage of literals such as FixNum (an always odd 'pointer' that you shift right by one bit to access the value) and Symbol (a 'pointer' that always has 0xff as the trailing byte that you shift right 1 byte to access the unique ID) without requiring object creation.
With this in mind, can someone enlighten me as to why Copying could not be used inside Ruby?
It seems as though it would be trivial for the GC to differentiate between literals and pointers as otherwise they would not be much use as literals.
However reading through the RHG, it is shown that Ruby allocates memory for objects in 20 byte blocks and that this results in all pointers therefore being multiples of four. This is handy as it allows the direct usage of literals such as FixNum (an always odd 'pointer' that you shift right by one bit to access the value) and Symbol (a 'pointer' that always has 0xff as the trailing byte that you shift right 1 byte to access the unique ID) without requiring object creation.
With this in mind, can someone enlighten me as to why Copying could not be used inside Ruby? It seems as though it would be trivial for the GC to differentiate between literals and pointers as otherwise they would not be much use as literals.