Building old revisions

Occasionally you may want to check out and build old versions of Chromium, such as when bisecting a regression or simply building an older release tag. Though this is not officially supported, these tips address some common complications.

This process may be easier if you copy your checkout (starting from the directory containing .gclient) to a new location, so you can just delete the checkout when finished instead of having to undo changes to your primary working directory.

Get compatible depot_tools

Check out a version of depot_tools from around the same time as the target revision. Since gclient auto-updates depot_tools, be sure to disable depot_tools auto-update before continuing by setting the environment variable DEPOT_TOOLS_UPDATE=0.

# Get date of current revision:
~/chrome/src $ COMMIT_DATE=$(git log -n 1 --pretty=format:%ci)

# Check out depot_tools revision from the same time:
~/depot_tools $ git checkout $(git rev-list -n 1 --before="$COMMIT_DATE" main)
~/depot_tools $ export DEPOT_TOOLS_UPDATE=0

Clean your working directory

To avoid unexpected gclient behavior and conflicts between revisions, remove any directories that aren't part of the revision you've checked out. By default, Git will preserve directories with their own Git repositories; bypass this by passing the --force option twice to git clean.

$ git clean -ffd

Repeat this command until it doesn't find anything to remove.

Sync dependencies

When running gclient sync, also remove any dependencies that are no longer required:

$ gclient sync -D --force --reset

Note that if you are attempting to build an old revision that is on a branch, you will need to use:

$ gclient sync -D --force --reset --with_branch_heads

instead.

Warning: gclient sync may overwrite the URL of your origin remote if it encounters problems. You'll notice this when Git starts thinking everything is "untracked" or "deleted". If this happens, fix and fetch the remote before continuing:

$ git remote get-url origin
https://chromium.googlesource.com/chromium/deps/opus.git
$ git remote set-url origin https://chromium.googlesource.com/chromium/src.git
$ git fetch origin

It may also be necessary to run the revision's version of build/install-build-deps.sh.

Build

Since build tools change over time, you may need to build using older versions of tools like Visual Studio.

You may also need to disable reclient (if enabled).

Get back to trunk

When returning to a normal checkout, you may need to undo some of the changes above:

• Restore depot_tools to the main branch.

• Clean up any _bad_scm/ directories in the directory containing .gclient.

• Revert your .gclient file if gclient changed it:

  Copy

  WARNING: gclient detected an obsolete setting in your .gclient file.  The
  file has been automagically updated.  The previous version is available at
  .gclient.old.