wasm-effect-handlers VS threads

This won't be a very deep answer, but to connect with the original post, programming in CPS is more closely related to delimited continuations than call/cc is because the continuations are just ordinary functions in the host language, unlike call/cc continuations which are a bit more complex.

As for why delimited continuations are not more popular, many people find shift/reset a bit difficult to program with. In particular the type systems for them are a bit odd and some variants like prompt/control don't have nice type systems for them. Currently, the closely related notion of (algebraic) effect handlers is quite popular in the functional language design community as something quite similar in expressive power but more intuitive for programming and with very natural typing. The Koka language has a lot of nice introductory resources if you are interested in learning more: https://github.com/koka-lang/koka . There's even a serious proposal for adding something based on these to webassembly: https://github.com/effect-handlers/wasm-effect-handlers .

Similarly for threads: https://github.com/webassembly/threads

Specifically I submitted this to draw attention to the latest comment in the thread: https://github.com/WebAssembly/threads/issues/177

It's a good deep dive into how a small, but well-intentioned, browser choice nearly a decade ago led to poor outcomes for the WebAssembly ecosystem.

The answer is: it's complicated. Which is most of the time the answer in the WASI world.

For this case it's complicated because some runtime supports https://github.com/WebAssembly/threads which mostly contains things like the spec for atomic but not the actual "threads" specs and then some runtimes (i.e wasmtime) also supports https://github.com/WebAssembly/wasi-threads which is one version of the threads. But a new proposal came into play https://github.com/abrown/thread-spawn so ... it's complicated.

There’s a proposal for threads

WebAssembly is having/going to have threads

https://github.com/WebAssembly/threads

It's disappointing to see the WebAssembly/threads proposal is still only in proposal state, despite existing since 2018. It being just a proposal stops languages like golang from actually implementing support for it, despite Chrome supporting it since v70.

Ah, I should have clarified that I mean the assembly instructions for atomics, rather than the JavaScript API. I.e. the opcodes listed here: https://github.com/WebAssembly/threads/blob/master/proposals...

Another point to add here is that the current wasm specification does not support threads although there is a proposal to add one. So I imagine that till the wasm specification includes it, we will continue to have only single threaded canisters.