Bug Reporting

All bugs should be filed in the GitHub main Emscripten repository Issue Tracker.

Please supply as much relevant information as possible, including:

  • Original source code.

  • Generated bitcode (.bc, .o or .ll)

  • Environment information — including emcc and clang versions (as reported by emcc -v).

  • Error symptoms.

  • Proposed solutions, ideally with a pull request.


Compile with EMCC_DEBUG=1 and grab the /tmp/emscripten_temp/emcc-* files (these include the bitcode and JavaScript in several stages). Note that the emscripten_temp directory should be emptied manually first, so it only contains new content!

LLVM, wasm-ld, clang, Binaryen bugs

If uncertain, bugs can always be posted to the main repository. But if you are sure a bug is in an upstream project, you can file it there:

  • LLVM bug tracker . For most issues use the “libraries” product and the “Backend: WebAssembly” component. For wasm-ld issues, use “lld” and “wasm”.

  • Binaryen bug tracker

Pull requests must (of course) go to the proper repository.

Site and documentation bugs

Documentation (site) bugs should be filed in the same Issue Tracker.

Include relevant information including:

  • The URL and title of the affected page(s).

  • A description of the problem.

  • Suggestions for a possible solution.


The Page bug link on the bottom-right of every page opens the Issue Tracker pre-seeded with the current page URL and title.