[nikki93]

Hello world just needs to call console.log, so doesn't need libc. Here's an example that builds without libc / emscripten to produce a very small wasm hello world: https://github.com/nikki93/cxx-wasm-freestanding There's actually some other stuff in there right now but console.cc is the main thing -- it calls consoleLog which js exposed to wasm from the js code at https://github.com/nikki93/cxx-wasm-freestanding/blob/master... .

You do need some JS code that asks the browser to run the wasm blob. You can't eg. just have a script tag that refers to a wasm blob yet.

libc does help with things like having an allocator or string operations etc., or for using C libraries that use libc. And that's where emscripten becomes helpful.

Browser functionality like the console or making html elements is exposed through JS interfaces, and the wasm needs to call out to those. But they may be directly exposed to wasm later (or they may already be at this point in new / experimental browser features).

[itslennysfault]

The hello world in this guide doesn't actually use console.log at all. It adds 2 numbers and sets the page content to the result. All it does is expose an add function from rust and call it from the javascript side.