I'm unfamiliar with WebAssembly, but I thought the spec was a little higher level. Two x86 apps might have the same op codes, but they don't always have the same calling conventions. How do you call a C function? You can't tell looking at the binary output, you only get the symbol name. Is it cdecl, stdcall, how many parameters and the names and types? Kotlin and Java work together, so do C# and F#.