Document UInt return type of objectid

[fonsp]

It took me some time to figure out that objectid returns a UInt. typeof(objectid(123)) gave me the false belief that the return type is UInt64.

Is the return type for hash also fixed to UInt?

[fredrikekre]

Is the return type for hash also fixed to UInt?

Looks like it

[Seelengrab]

I'm confused - what's the return type of those two functions on a 32-Bit system? UInt is just an alias for either UInt64 or UInt32 after all, is the return type system dependent here?

[fonsp]

is the return type system dependent here?

That's right, it returns a UInt, which is UInt32 or UInt64 depending on your system. I think this has something to do with pointers.

[Seelengrab]

Looking through hashing.h and builtins.c, it's not immediately obvious to me why this is system dependent (other than it relying on pointer sizes), but I can tell that it would be a lot of work (and breaking at that) to change that to be consistent across systems. May also not be worthwhile 🤷‍♂️

Maybe there are more undocumented cases of methods not agreeing across systems, even though they're from the same version?

[fonsp]

@Seelengrab Unfortunately I am not the right person to ask (not a computer scientist), but you could restart this discussion on https://discourse.julialang.org/ to reach people who also understand this subject!