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kripken edited this page Dec 8, 2012 · 96 revisions

Emscripten is an LLVM to JavaScript compiler. It takes LLVM bitcode (which can be generated from C/C++ using Clang, or any other language that can be converted into LLVM bitcode) and compiles that into JavaScript, which can be run on the web (or anywhere else JavaScript can run).

Using Emscripten, you can

  • Compile C and C++ code into JavaScript and run that on the web
  • Run code in languages like Python as well, by compiling CPython from C to JavaScript and interpreting code in that on the web

Demos

Other Examples

  • zpipe - zlib compiled to JS
  • zee.js - Another port of zlib to JS (focused on compressing/decompressing of gzip files)
  • lzma.js - LZMA ported to JS
  • sql.js - SQLite ported to JS

Useful Things

Get in Touch

Bug Reports

You can file issues here on GitHub. If relevant, please supply the original source, the generated .ll, and the generated .js files (in a gist, pastebin, or any other method). It's very helpful to compile with EMCC_DEBUG=1 in the environment, and grab the /tmp/emscripten_temp/emcc-* files (note - you should empty that directory manually before, so it only contains new content), that will include the bitcode, ll, and JS in several stages.

Contributing

Anyone is welcome to join us in developing Emscripten. Feel free to contact us on IRC or on the mailing list (links above), or through issues here on GitHub.

Patches can be submitted either in issues (as a gist is probably most convenient), or as pull requests, either is fine. When submitting patches, please:

  • Add yourself to the AUTHORS file (if you aren't already there). By adding yourself, you agree to license your code under the project's open source licenses (MIT/LLVM).
  • You should run all the automatic tests and make sure they pass (python tests/runner.py). Patches that are simple enough (for example, just add library functions that were not used before) might not need this, but most will. Please mention in the pull request or issue which tests you ran.
  • If you did not run all the automatic tests, please make your pull request to incoming, not master. Code in incoming will have tests run on it, and will later merge to master when they all pass.
  • If you add any new functionality or fix an existing bug, add an automatic test to tests/runner.py.
  • Please do not include merge commits in pull requests; include only commits with the new relevant code.

Branches of interest

  • master - Always safe to pull from, the test suite always passes on it
  • incoming - Where new code lands before tests have been done
  • llvmsvn - Where work to support a new version of LLVM lands. Activity typically begins near the end of an LLVM 6-month dev cycle. When LLVM launches the new version, we merge this branch to master and incoming, at which point our support officially moves to that new LLVM version (we only support one at a time)

Thanks to juj we have test results for master and incoming on multiple platforms.

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