If it is on purpose, what an absolutely diabolical way to ensure javascript language dominance in the browser: give people a way to port their language to the browser, but make it incredibly difficult to do anything.
[0] https://github.com/WebAssembly/interface-types/blob/master/p...
The Emscripten SDK offers helper functions to marshal high level data types like Javascript strings to UTF-8 encoded C strings on the WASM heap and back to JS, so it's not that bad.
DOM access can be achieved with helper libraries which call out into JS. And since any sort of DOM manipulation is extremely slow anyway there's not much of a performance difference even with the overhead of calling out from WASM into JS (which actually is quite fast nowadays).
The good one!
UTf-8, NOT null terminated, pascal like.
ie: what rust have:
https://doc.rust-lang.org/std/string/struct.String.html
REPEAT the mistakes of C (and considering the security angle! in a browser!) must be a big no.
So you get all the fun to corrupt linear memory C style.
Agreed, but as consumer from WASM modules that isn't your option to make.
> WASM's job is to prevent code inside the sandbox from escaping the sandbox, not to prevent memory corruption inside the sandbox.
That is not better than a typical OS process, just it happens to be randomly downloaded into my computer.
On the other hand I need to admit that I would have not forseen some of the more recent use cases for WebAssembly
https://bytecodealliance.org/articles/making-javascript-run-...
which can be reminescent of the "docker daemon running as root" issue.
So, given this is a fact, the best course of action is chosen the most safe alternative.
And for everyone else? Well an array of bits ant let the host/callers that are the only that know their own stuff deal with it.
INCLUDING Js.
string ≡ (list char)
Basically, this is "the most safe alternative"??!
A safe one. Your sample is that - except I think is better if is a utf-8 string, but this one works for me too-. What will be worrisome is if is made to be like in C.
Rust (or C++) strings are not pascal strings. In pascal strings, the "string buffer" also contains the length information, and historically it was all bytes with a length byte at the start, which was why your strings started at index 1 and limited to 254 bytes.
It's possible to modernise this style of strings to be less crummy (that is essentially what sds does), but C++/Rust string are a third take where the length (and capacity) are stored separately from the string buffer, and that buffer is always on the other side of a pointer (ignoring SSO, which Rust sadly doesn't have due to the original interface definition).
To be fair, I don't know how many clock cycles creating, destroying or modifying a DOM node costs on average, but most likely "a lot" compared to the overhead of a WASM to JS call because a lot more machinery is involved.
But there's no reason you must write this yourself. Others have done the hard work for you and written libraries.
https://brendaneich.com/2015/06/from-asm-js-to-webassembly/
edit: from the linked article, in case it isn't clear, an HN comment by eich:
"Sure, in userland many languages compile to assembly. Hmm, where have I heard that word lately?"[1]
The lack of a DOM API is something I sorely miss as well. It's currently possible (and not that hard, you can just interact with JS), but comes with such performance overhead that you lose the entire benefit of WASM.
But as you have pointed out, the missing layer on top i.e. the 'thing we can practically use' is a big gaping hole and it's a little bit diabolical.
The fact that JS has gotten so much faster and the lack of both higher-level abstractions and notably a really good 'bridge' to JS means it's lagged in terms of material applicability.
I know it's an existing proposal for WASM, but it feels so massively out of scope. If the issue is having to include runtimes in the WASM binary it might be more useful to think about how we could serve runtimes in a more efficient way.
(At least, that's what it used to be; I haven't been involved in WebAssembly for a long time.)
GC performance depends more on the program than the language.
But regardless, the hardest parts of getting to advanced GCs, such as concurrent and parallel algorithms are usually very deep assumptions of single-threadedness and uninterruptibility that are debt in the runtime. It usually doesn't help that most runtimes are written in C/C++ and suffer that environment's complete uncooperativeness[1] in finding and manipulating roots.
[1] To the point of seeming hostility. It's been how many years and LLVM still fights against supporting stack maps?
The memory profile of JavaScript applications tends to look a lot like the memory profile of typical Java applications. It tends to be a law of large numbers.
Now if you want to talk about details of how we implement runtimes that do have observable GC details, like weak callbacks, Java's zoo of reference types, etc, then let's do that, because Wasm GC will eventually need to have low-level mechanisms to support those.
But if we're talking about a Wasm engine GC's ability to allocate, trace, move (or not!) little blocks of memory around, then I don't see any fundamental stumbling blocks to making that mechanism efficient and universal.
So if a future WASM GC doesn't offer APIs for such capabilities, it is useless from those runtimes point of view.
Java has an API for executing the GC on demand, and VM engineers I have talked to over the years think it's a knob that apps shouldn't have.
Wasm already supports multiple return values, so you don't need to box value types on any boundary--they can be flattened whereever they occur.
Pinning memory has to do with interfacing native code that could potentially do unsafe things. That doesn't fit into wasm's model, and would only be necessary for interacting with platform APIs, which are being designed not to need that. Same for "marshalling to native code".
I don't understand what you mean by GC regions. Realtime Java had GC regions and a complex system for trying to allow threads to run without touching the heap. It really didn't go well. I think if regions are useful for a GC, the engine should do inference of them, because adding regions to the type system infects everything.