I've been working on an Emscripten emulation layer for a fledgling startup, and it's just a huge bitch. Seriously, Emscripten is the worst designed project I've ever seen. It embeds constants into a js file that it spits out. It turns out you can't fucking run the wasm that Emscripten emits without these magic constants from the js file.

Additionally, all the wasm imports that emscripten specifies are weirdly cased, with apparently no naming convention. They also use some weird, shitty vararg implementation when it already fucking knows exactly how many arguments are going to get passed to an import.

Also, there are a ton of broken things left over from when emscripten compiled to asm.js that they never bothered to replace with features from wasm. God knows how it even works.