Oh, alright. We are speaking about two different things. I was thinking about compilation and specifically supporting complex language features which are mostly handled by a compiler frontend which is this case is clang. And it seems that you are thinking about runtime libraries (or the whole tool chain).
Re:WebAssembly 101: A developer’s first steps
by ThePhysicist on Tuesday June 06, 2017 @11:31AM
(#14497981)
Ah yes you're right, that part is luckily covered by LLVM.
You must not forget that JS does not provide support for many of the things that are required to run a C program (e.g. printing), so emscripten needs to take care of providing alternative implementations for all these things.