Well yes, the need to download a new runtime for every app you run is a problem if thst runtime is several megabytes.

C++ isn't accessible to web developers compared to Rust. It's not just that I can't be bothered to learn, it's that I'm scared of all the security vunerabilities and memory corruption bugs I will write while I'm learning. And wjy put in that effort when I can learn Rust more easily, and get the ongoing benefits of my code being safe and reliable.

True, D also competes here. I should probably have put D on the list. Although my understanding is that a large part of the D ecosystem still relies on GC.

Most runtimes are fairly small, and most issues could be done away with by either the browser storing common runtimes (Search for x, then checking hashes etc.) or by compiling statically against the parts you actually use.

This is still not conclusive, as the runtimes will probably have to be significantly modified (at the ABI/System level, so around the edges) given that they will have to get memory from the browser etc. This leaves much room for WASM specific optimisation, especially given that the actual (let's say) garbage collector implementation is probably quite small compared to the code used to interface to it.

Writing C++ defensively (i.e. Do what the guidelines tell you, Preach Andrei and Bjarne etc), and using sanitizers cleans up a huge amount of C++ code.

> Writing C++ defensively (i.e. Do what the guidelines tell you, Preach Andrei and Bjarne etc), and using sanitizers cleans up a huge amount of C++ code.

Well sure, but the joy of Rust is that I don't have to worry about any of that. I can write my code naively, and the compiler will throw an error if I do anything stupid.

> This is still not conclusive, as the runtimes will probably have to be significantly modified (at the ABI/System level, so around the edges) given that they will have to get memory from the browser etc. This leaves much room for WASM specific optimisation

Certainly if/when this happens, other languages will be a lot viable in the compile-to-wasm. But you can run Rust (and C/C++) in the WASM runtime without issues today. And Rust even has a number of high-level libraries which provide binding to JavaScript APIs (e.g. https://github.com/rustwasm/wasm-bindgen)