Faster compilations for everyone?

If you’re following this blog, you may be aware of the recent work on shared compilation cache. This has been deployed with great results on Mozilla’s try server for all platforms (except a few build types, like ASAN or valgrind), and is being tested for Linux/Android builds on b2g-inbound (more on that in subsequent posts).

A side effect of the work to make it run on all platforms is that it now works to build Firefox on Windows, although it requires a specific setup. And since recently, it’s also possible to use it with local storage instead of S3. This means we now have a (basic) ccache for Windows that works to build Firefox.

If you wish to try it, here is what you need to do:

  • Clone the repository from github:

    $ git clone

  • Add the following to your mozconfig:

    ac_add_options "--with-compiler-wrapper=python2.7 path/to/sccache/"
    export _DEPEND_CFLAGS='-deps$(MDDEPDIR)/$(@F).pp'
    mk_add_options "export CC_WRAPPER="
    mk_add_options "export CXX_WRAPPER="
    mk_add_options "export COMPILE_PDB_FLAG="
    mk_add_options "export HOST_PDB_FLAG="
    mk_add_options "export MOZ_DEBUG_FLAGS=-Z7"

    Update: Currently, path/to/sccache/ needs to be a windows-like path (as opposed to msys/cygwin path) with forward slashes.

  • Then set the SCCACHE_DIR environment variable to some local directory.
  • And build happily.

A few things to note:

  • As of writing, sccache doesn’t support cleaning up the storage directory, so it will grow indefinitely (until you clean it up yourself).
  • Because the MSVC preprocessor is not exactly fast, and because sccache doesn’t have a direct mode like ccache, it doesn’t make as much difference as ccache does.
  • It also works on non-windows, but doesn’t require all the mozconfig changes, except for the --with-compiler-wrapper line.

Play with it and feel free to fork it on github, and improve it. Pull requests encouraged.

2014-05-08 09:36:24+0100


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