Ghc now runs in your browser

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ghc itself can now run purely client-side in the browser, here’s a haskell playground demo. terms and conditions apply, and i’ll write up more detailed explanation some time later, but i thought this is a cool thing to show off how far the ghc wasm backend has advanced :slight_smile:

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This is very cool! I wonder how easy it would be to load some packages; cabal in the browser when? I’m also wondering how usable Agda in the browser would be.

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I think I found a bug: ghc options persist even after I change them.

Also -with-rtsopts=-s does not work, sadly. Edit: Ah, that’s because it is interpreted.

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This is awesome!
Perfect for building a fully interactive Haskell online course! :star_struck:

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Awesome work!

Browser reports:

  • In Brave, after a few seconds unresponsive, it loads. It shows: “Could not create web worker(s). Falling back to loading web worker code in main thread, which might cause UI freezes. Please see GitHub - microsoft/monaco-editor: A browser based code editor
    You must define a function MonacoEnvironment.getWorkerUrl or MonacoEnvironment.getWorker”. The Run button works.
  • In Safari, the same message, but the Run button remains disabled.
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Excellent work - the efforts to bring Haskell to WASM are a huge boon to our ecosystem and userbase!

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Can’t run it on my tablet (wasm), curious: is this running the type checker or also code gen to wasm?

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It runs the code, but it seems like it uses the bytecode interpreter.

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What modifications were to GHC for it to be compiled to WASM?

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cabal won’t work in the browser due to lack of process support; but it’s possible to use wasm32-wasi-cabal to precompile some third party packages to wasm and make this playground support them as well.

you might be interested to check GitHub - agda-web/agda-wasm-dist: Distributions of Agda executable compiled into WebAssembly.; afaik they even compiled GitHub - agda/agda-language-server: Language Server for Agda to wasm, not sure how usable it is currently

thanks for the report! i pushed an update which should have fixed it.

that’s right; ghc in browser can’t invoke the c compiler and it can only interpret haskell modules via bytecode.

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thanks for the reports! a few seconds of freeze during start-time is expected, since it needs to download ~50M of a rootfs tarball and extract it, then link the ghc library and all its dependencies. as for safari, it’s strange since i i just landed a workaround for a webkit bug that breaks the wasm dynamic linker a few days ago, i’ll take a closer look later.

the ghc library already mostly works when compiled to wasm, and it can parse/typecheck/desugar stuff. the bottleneck is the linker/loader part, for it to be useful it needs to be able to dynamically load and execute haskell code. i landed a couple of ghc patches recently to push towards that direction, and the last one that gets us towards the haskell playground (not landed yet) is Draft: Support running GHC fully client-side in the browser (!15000) · Merge requests · Glasgow Haskell Compiler / GHC · GitLab

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Which packages are installed by default?

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now chrome will consume even more memory :stuck_out_tongue:

Awesome work!