Make Rust work with emscripten

[steveklabnik]

Issue by brson
Wednesday Apr 18, 2012 at 20:44 GMT

For earlier discussion, see rust-lang/rust#2235

This issue was labelled with: A-an-interesting-project, A-build, A-runtime, E-hard, I-wishlist in the Rust repository

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I've spent some time poking at this problem and rustc now generates code that emscripten can translate, but the compiled javascript fails when it hits a runtime function. The next step is to start building the runtime using emcc as the compiler. Stub out all the things that don't build behind EMSCRIPTEN ifdefs.

Emscripten is adding a way to treat inline assembly as javascript, so all the parts of the runtime that don't build with emscripten can be implemented inline with javascript.

Alternately, we could reimplement the runtime piecemeal in javascript and not bother compiling it from C++ at all. This approach isn't recommended.

[aidanhs]

Looks kinda-working with a bit of hackery - http://www.reddit.com/r/rust/comments/2ylzkx/a_game_written_with_piston_running_on_the_web_via/

[antonkulaga]

This feature looks very promising. I wonder, is the expecting performance going to be better than with native (handwritten) Javascript?

[withoutboats]

@antonkulaga it should perform much better in a browser that supports asm.js - tests show asm.js is within about a factor of 2 of native performance.

[ticki]

Relevant:

• http://myth.aaronlindsay.com/test/
• https://github.com/AerialX/cargo-build
• https://github.com/tomaka/cargo-emscripten

[DiamondLovesYou]

Also relevant:

• https://github.com/DiamondLovesYou/rust/tree/libstd-pnacl-rebase

[chpio]

it's not working any more: AerialX/cargo-build#2

[chpio]

[tomaka]

@t128 The next step is basically rust-lang/rust#26505

[bennycode]

@tomaka rust-lang/rust#26505 is closed. So how good are chances to see a working Rust -> JavaScript transpiler? Has anyone made progress?

[ticki]

This is not exactly a Rust -> JavaScript transpiler, but there is bilalhusain/dust, which is a language which is very similar to Rust (but as it's JS, it doesn't have all the fancy memory mangement of rust, it uses a gc). I'm not sure if that's relevant.

Also why make a transpiler, instead of getting it to work with emscripten?

[tomaka]

@bennyn The previous PR has been closed in favor of rust-lang/rust#28355