Important! So, you’re asking about multithreading in Emscripten? How does it work? What are the limitations?
Okay, so here’s the lowdown as I understand it. WebWorkers are the base implementation. At one point in time, SharedArrayBuffers were used on top of these to effectively implement multithreading, but for the time being this feature was disabled in light of the Meltdown and Spectre vulnerabilities. Until the feature gets re-enabled, true multithreading in Emscripten is out of the game.
Okay, so what features do WebWorkers provide you with? Can you start
a process and deliver messages to it like you would with Unix I/O?
Unfortunately, the setup seems more contrived. You can deliver
messages, but messages are processed in a batch manner. A message,
one delivered, calls an event notification, and the next message
processing will be delayed until that function exits. Sorry, looks
like Unix-like read() is not supported.
20180611/DuckDuckGo emscripten webworkers
20180611/https://floooh.github.io/2013/01/13/multithreading-in-emscripten-with-html5.html
20180611/DuckDuckGo emscripten threads
20180611/https://stackoverflow.com/questions/27473959/thread-using-emscripten#31466135
20180611/https://kripken.github.io/emscripten-site/docs/porting/pthreads.html
20180611/https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API
20180611/https://developer.mozilla.org/en-US/docs/Web/API/Worker
20180611/https://developer.mozilla.org/en-US/docs/Web/API/EventListener