I'll take a stab at your question. > Are there fundamental issues with JVM bytecode that make it impossible/impractical to have c++/rust/LLVM compile to it? L

I'll take a stab at your question. > Are there fundamental issues with JVM bytecode that make it impossible/impractical to have c++/rust/LLVM compile to it? Lack of pointers. Lack of true structs. Different memory model. Enforced class/object model. WebAssembly has a memory model which is very close to a generic CPU. My understanding of what made WASM necessary - You don't want a GC? You don't get a GC. You want full control over your memory layout? You get a raw growable slab of memory with raw pointers.