Tagged pointer implementation

[Sze]

@SillyProgramming

but if the tag is inside the usize would the pointer be broken.
What is I am not understanding?

On most systems not every bit in a pointer will be used, but it depends on the target.
Here is a comment that has more details:

How to free a type erased field?

It’s also pretty easy to make this pointer tagging approach type safe in zig. If you use the lower bits, the number you can use generally just depends on the alignment of the data you point to and is quite portable. So up to 3 bits for 8 byte aligned pointers. If you use the upper bits you usually have more space but it’s architecture (and even cpu) dependent how much space you have and sometimes it might not even be possible because some other metadata might be stored there(like PAC and MTE o…

Basically pointer tagging is a bit of a trick/hack to store extra information in pointers, but it requires understanding how exactly pointers work on the target architecture, these “unused bits” are also increasingly used for other purposes, so basically you have to make sure you understand the target hardware and the software running on it, to make sure you aren’t doing something that doesn’t work. Using alignment bits is the simplest and most portable.