Support Threads.Atomic{Bool}

[NHDaly]

Could we add Bool to the list of types supported by Threads.Atomic? Currently atomics only supports int types and float types, but I don't see any reason why it couldn't also support booleans! :)

For now as a workaround, you have to use an x = Threads.Atomic{UInt8} and always check if x != 0 instead of just if x.

I couldn't find either a github issue or discourse thread about this already, sorry if this is a duplicate. Thanks! :)

[NHDaly]

Oh, actually, I just came across this comment when checking to see how atomics are implemented:

julia/base/atomics.jl

Line 29 in 84e68f3

# TODO: Support Bool, Ptr

(# TODO: Support Bool, Ptr)

So I guess this is an already-desired TODO. I didn't find an Issue for it, but sorry if this is a duplicate.

---

That said, would implementing this be more complicated than simply adding Bool to the list of atomictypes? That is, changing this line:

julia/base/atomics.jl

Line 30 in 84e68f3

const atomictypes = (inttypes..., floattypes...)

to const atomictypes = (inttypes..., floattypes..., Bool)?

[NHDaly]

Ah, so I guess one complication would be deciding what to do about the arithmetic atomic_* functions.

For example, what should atomic_add!(x::Atomic{Bool}, val::Bool) even mean? My gut says it simply shouldn't be defined. But that will mean at least a slight refactoring of the type and its functions...

We could define ArithmeticTypes = Union{(inttypes..., floattypes...)...}, and change those function definitions to atomic_add!(x::Atomic{T}, val::T) where T<:ArithmeticTypes? Does that seem like an okay approach?

[kpamnany]

Nice work, appreciated!

[NHDaly]

haha thanks. in the PR, I just basically did what i described here in the issue: added where T<:ArithmeticTypes to atomic_add and atomic_sub.