RegEx101 VS PeLib

> I wonder if this could be used to make C# webassembly more viable.

You might enjoy reading this GitHub thread [0] where the community contributed a WASM library wrapping the C# regex code so that regex101.com could have a "C# mode". Lots of nerd sniping about reducing the payload size.

(There's also another thread [1] discussing the minification of a rust version of that same regex101 wasm library to provide a "rust mode" using @burntsushi's regex crate.)

[0]: https://github.com/firasdib/Regex101/issues/156

[1]: https://github.com/firasdib/Regex101/issues/1208

That’s correct, compiled to WASM. You can see all the nitty gritty here https://github.com/firasdib/Regex101/issues/1208

Excellent comparisons. ~150KB without unicode would make Rust the smallest wasm on Regex101 as far as I can tell. pcrelib comes in at 198KB. Personally, I think ~400KB with unicode features is just fine for .wasm size. The heaviest flavor C# is around 4.91MB and was added back in February of this year. They also had a performance comparison which would also be interesting.

I'm usually working with the third edition of the ISO 23271 standard, which corresponds to ECMA 335 5th Edition. There is also the book ".NET IL Assembler" (2014) by Serge Lidin which gives some additional context and a good structure to learn the details. My compiler is written in C++, not depending on the .Net framework; I don't use the reflection and emit features of .Net, but https://github.com/rochus-keller/Pelib/ to generate assemblies; also the generated code only requires minimal mscorlib.dll features, so I can use a minimal CLR.

Most of my languages have VM backends; see e.g. https://github.com/rochus-keller/Oberon; I implemented different backends generating LuaJIT bytecode; a year ago I switched to Mono which is based on ECMA-335; here is a discussion why I switched: https://github.com/rochus-keller/Oberon/releases/tag/IDEv0.9.0; I implemented utility libraries for both LuaJIT and CIL bytecode; see https://github.com/rochus-keller/LjTools/, https://github.com/rochus-keller/Pelib/ and https://github.com/rochus-keller/MonoTools/. I evaluated many VMs and think the mentioned ones are best suited. There were a lot of challenges with both technologies, what is to be expected, and too much to describe here.

And as I understand now achieving optimal performance with CoreCLR requires inside know-how of RyuJIT and Roslyn (which I don't have anyway), i.e. ECMA-335 alone is not sufficient; the actual compilation target to achieve optimal performance with CoreCLR is therefore Roslyn, not ECMA-335; of course I could generate C# instead of IL, but then I would depend on the framework and slow down the compiler. My current code generator based on https://github.com/rochus-keller/PeLib is about 30 times faster than ILASM.