alt Hacker NewsThere are a thousand reasons, which is why nobody is doing it. They're orthogonal. Problems WASM/WASI doesn't solve:
- Building / moving file hierarchies around
- Compatibility with software that expects Linux APIs like /proc
- Port binding, DNS, service naming
- CLI / API tooling for service management
And about a gazillion other things. WASI, meanwhile, is just a very small subset of POSIX but with a bunch of stuff renamed so nothing works on it. It's not meaningfully portable in any way outside of UNIX so you might as well just write a real Linux app. WASI buys you nothing.
WASM is heavily overfit to the browser user case. I think a lot of the dissipated excitement is due to people not appreciating how much that is true. The JVM is a much more general technology than WASM is which is why it was able to move between such different use cases successfully (starting on smart TV boxes, then applets, then desktop apps, then servers + smart cards, then Android), whereas WASM never made it outside the browser in any meaningful way.
WASM seems to exist mostly because Mozilla threw up over the original NaCL proposal (which IMO was quite elegant). They said it wasn't 'webby', a quality they never managed to define IMO. Before WASM Google also had a less well known proposal to formally extend the web with JVM bytecode as a first class citizen, which would have allowed fast DOM/JS bindings (Java has an official DOM/JS bindings API for a long time due to the applet heritage). The bytecode wouldn't have had full access to the entire Java SE API like applets did, so the security surface area would have been much smaller and it'd have run inside the renderer sandbox like V8. But Mozilla rejected that too.
So we have WASM. Ignoring the new GC extensions, it's basically just regular assembly language with masked memory access and some standardized ABI stuff, with the major downside that no CPU vendor uses it so it has to be JIT compiled at great expense. A strange animal, not truly excellent at anything except pleasing the technical aesthetic tastes of the Mozillians. But if you don't have to care about what Mozilla think it's hard to come up with justifications for using it.
Replies
> WASM seems to exist mostly because Mozilla threw up over the original NaCL proposal (which IMO was quite elegant). They said it wasn't 'webby', a quality they never managed to define IMO.
No, Mozilla's concerns at the time were very concrete and clear:
- NaCl was not portable - it shipped native binaries for each architecture.
- PNaCl (Portable Native Client, which came later) fixed that, but it only ran out of process, making it depend on PPAPI, an entirely new set of APIs for browsers to implement.
Wasm was designed to be PNaCl - a portable bytecode designed to be efficiently compiled - but able to run in-process, calling existing Web APIs through JS.
> with a bunch of stuff renamed
And a capability system and a brand new IDL, although I'm not sure who the target audience is...
> it's basically just regular assembly language
This doesn't affect your point at all, but it's much closer to a high-level language than to regular assembly language, isn't it? Nonaddressable, automatically managed stack, mandatorily structured control flow, local variables instead of registers, etc.
> WASI, meanwhile, is just a very small subset of POSIX but with a bunch of stuff renamed so nothing works on it.
WASI fixed well-known flaws in the POSIX API. That's not a bad thing.
> the major downside that no CPU vendor uses it so it has to be JIT compiled at great expense.
WASM was designed to be JIT-compiled into its final form at the speed it is downloaded by a web browser. JS JIT-compilers in modern web browsers are much more complex, often having multiple compilers in tiers so it spends time optimising only the hottest functions.
Outside web browsers, I'd think there are few use-cases where WASM couldn't be AOT-compiled.