exception-handling VS llvm-project

Interesting article, thanks!

Notes on the issues mentioned there:

* The need for a manual shadow stack: This is fixed in WasmGC (in the same way it works in JS, as the link mentions).

* Lack of try-catch: This is fixed by the Wasm exception handling proposal, which has already shipped in browsers, https://github.com/WebAssembly/exception-handling/blob/main/...

* Null checks: Mostly fixed by WasmGC. The spec defines non-nullable local types, and VMs can use the techniques the article mentions to optimize them using signals (Wizard does, for example).

* Class initialization: This is a difficult problem, as the article says. J2Wasm and Binaryen are working to optimize it through static analysis at the toolchain level. Here is a recent PR I wrote that makes progress there: https://github.com/WebAssembly/binaryen/pull/6061

* The vtable overhead issue the article mentions may be a problem. I'm not aware of good measurements on it, through. There are some ideas on post-MVP solutions for method dispatch that might help, but nothing concrete yet.

* Checks for null and trapping: There has been discussion of variants on the GC instructions that throw instead of trap. Measurements, however, have not shown it to be a big problem atm, so it is low priority.

The author is right that stack walking, signals, and memory control are important areas that could help here.

Overall with WasmGC and exceptions we are in a pretty good place for Java as emitted by J2Wasm today: it is usually faster than J2CL which compiles Java to JavaScript. But there is definitely room for improvement.

It uses https://github.com/WebAssembly/exception-handling/blob/master/proposals/exception-handling/Exceptions.md which is actually supported by all major browsers already.

Yep, you're right. It's also more than just the DOM, it's web APIs in general, such as fetch, audio, webgl/webgpu, etc. WASM still needs GC, exceptions, and WASI to be able to fully interop with any host without any of the current limitations. This'll take a few years. I'm looking forward to the future in which I will be shipping WASM-only web apps to my users.

Its a part of the wasm plan to support gc https://github.com/WebAssembly/gc exceptions https://github.com/WebAssembly/exception-handling

As of Node.js 17, the v8 JavaScript engine has been updated to v9.5. The changes in this release are primarily aimed at expanding internationalization for dates and calendars as well as for the output of time zones. It also implements the WebAssembly Exception Handling proposal, designed to reduce overhead compared to current JavaScript-based workarounds.

Agreed, although at some point in a not very far feature most of those missing features will resolved. So in my mind is just a matter of time. The Wasm Community group is doing an awesome work on that :)

Here are a few examples of what needs move forward in Wasm:

* [1] Wasm Exceptions Handling: Right now Wasm is missing a way to handle exceptions natively (C++ programs can only compile to Wasm using the asyncify or longjmp/setjmp tricks via Js try/catch)

* [2] Wasm GC: Wasm Binary files are quite big (specially in interpreted languages). This is partially caused by the GC being included in the Binary itself. The GC proposal will solve this while also providing faster execution.

* [3] Wasm 64-bit Memory: currently Wasm can only operate with 32-bit data. In some contexts you may want you operate with more than 4GB of memory (for example, when operating over terabytes of data). The 64-bit memory proposal will solve that.

[1]: https://github.com/WebAssembly/exception-handling

'Computer Architeture: A Quantitative Apporach" and/or more specific design types (mips, arm, etc) can be found under the Morgan Kaufmann Series in Computer Architeture and Design.

"Getting Started with LLVM Core Libraries: Get to Grips With Llvm Essentials and Use the Core Libraries to Build Advanced Tools "

"The Architecture of Open Source Applications (Volume 1) : LLVM" https://aosabook.org/en/v1/llvm.html

"Tourist Guide to LLVM source code" : https://blog.regehr.org/archives/1453

llvm home page : https://llvm.org/

llvm tutorial : https://llvm.org/docs/tutorial/

llvm reference : https://llvm.org/docs/LangRef.html

learn by examples : C source code to 'llvm' bitcode : https://stackoverflow.com/questions/9148890/how-to-make-clan...

See

https://github.com/llvm/llvm-project/issues/88344

https://fortran-lang.discourse.group/t/flang-new-how-to-forc...

You can never mistake type_declaration with an identifier, otherwise the program will not work. Aside from that constraint, you are free to name them whatever you like, there is no one standard, and each parser has it own naming conventions, unless you are planning to use something like LLVM. If you are interested, you can see examples of naming in different language parsers in the AST Explorer.

> There is one way to make the LLVM JIT compiler more usable, but I fear it’s going to take years to be implemented: being able to cache and reuse compiled queries.

Actually, it's implemented in LLVM for years :) https://github.com/llvm/llvm-project/commit/a98546ebcd2a692e...

> It's true, this was a CVE in Rust and not a CVE in C++, but only because C++ doesn't regard the issue as a problem at all. The problem definitely exists in C++, but it's not acknowledged as a problem, let alone fixed.

Can you find a link that substantiates your claim? You're throwing out some heavy accusations here that don't seem to match reality at all.

Case in point, this was fixed in both major C++ libraries:

https://github.com/gcc-mirror/gcc/commit/ebf6175464768983a2d...

https://github.com/llvm/llvm-project/commit/4f67a909902d8ab9...

So what C++ community refused to regard this as an issue and refused to fix it? Where is your supporting evidence for your claims?

For everyone else looking for the magic in this almost 7k lines monster, look at line 6610 [1].

[1] https://github.com/llvm/llvm-project/blob/8ec28af8eaff5acd0d...

Through value tracking. It's actually LLVM that does this, GCC probably does it as well, so in theory explicit bounds checks in regular C code would also be removed by the compiler.

How it works exactly I don't know, and apparently it's so complex that it requires over 9000 lines of C++ to express:

https://github.com/llvm/llvm-project/blob/main/llvm/lib/Anal...

https://github.com/llvm/llvm-project/blob/main/flang/docs/F2...