How to test new clang versions with try

Mac OS X builds of Firefox now use clang, and as work was put in to make the switch happen, this necessitated testing individual versions of clang. This means we have infrastructure in place that makes it (relatively) easy to run tests on the try server with even patched versions of clang. Here's how you do it:

Step 1: Build your version of clang

This should be trivial, although one wrinkle is that you need to specify where the gcc-toolchain is located explictly (/tools/gcc-4.5-0moz3 for now). If you're like me and lazy, you can just use the build-clang.py script to make the final tarball, after tweaking it to include your patch. Note that it expects to be located in specific directories (/builds/slave/moz-toolchain in particular). If you're building by hand, be sure to make a .tar.bz2 of the

Step 2: Place packages in appropriate location

The next script assumes things in particular places. It wants a directory layout that looks like:

$ pwd
/path/ending/in/clang-SVN revision
$ ls
clang-darwin.tar.bz2 clang-linux32.tar.bz2 clang-linux64.tzr.bz2

Step 3: Make manifests

This script is create-manifest.py, which has a requirement of simplejson 2.5 (which is newer than what mozilla-central's virtualenv python provides, alas). If you don't have a new enough python environment, just eliminate the item_sort_key=key_sort parameter and live with the fact that your output files are going to change more lines when importing to mozilla-central. This step produces files like darwin.manifest; these should be copied to browser/config/tooltool-manifests/platform/clang.manifest and the respective releng.manifest. It will also produce files with long, ugly filenames that look like someone dumped out a SHA512 hash as the filename (this is in fact what happens).

Step 4: Upload the files

First, copy the SHA512-named filenames somewhere public, like people.mozilla.org. Next, go into the mozconfigs to use clang instead of gcc. An example is here:

export CC="$topsrcdir/clang/bin/clang -fgnu89-inline"
export CXX=$topsrcdir/clang/bin/clang++

Disabling warnings as errors is also probably a good idea, since it seems that Linux people can't stop those extra semicolons sneaking in. Then, push to try and hope for the best!