Red-Black tree storing color without additional memory requirements

[bearophile]

safety0ff:

> Since the GC supports interior pointers, I think you can 
> justify using the least significant bits as long as the size 
> and alignment of the pointed object guarantee that the pointer 
> + tag will always lie inside the memory block.

From:
http://dlang.org/garbage.html

> Do not take advantage of alignment of pointers to store bit 
> flags in the low order bits:

Bye,
bearophile