Updating Clang format binaries

Instructions on how to update the clang-format binaries that come with a checkout of Chromium.


You‘ll need a Windows machine, a Linux machine, and a Mac; all capable of building clang-format. You’ll also need permissions to upload to the appropriate google storage bucket. Chromium infrastructure team members have this, and others can be granted the permission based on need. Talk to ncarter or hinoka about getting access.

Pick a head svn revision

Consult http://llvm.org/svn/llvm-project/ for the current head revision. This will be the CLANG_REV you'll use later to check out each platform to a consistent state.

Build a release-mode clang-format on each platform

Follow the official instructions here: http://clang.llvm.org/get_started.html.

Windows step-by-step:

# [double check you have the tools you need]
where cmake.exe  # You need to install this.
where svn.exe  # Maybe fix with: set PATH=%PATH%;D:\src\depot_tools\svn_bin
"c:\Program Files (x86)\Microsoft Visual Studio 14.0\vc\vcvarsall.bat" amd64_x86

set CLANG_REV=198831  # You must change this value (see above)

[from a clean directory, check out and build]
rmdir /S /Q llvm
rmdir /S /Q llvm-build
mkdir llvm
mkdir llvm-build
svn co http://llvm.org/svn/llvm-project/llvm/trunk@%CLANG_REV% llvm
cd llvm\tools
svn co http://llvm.org/svn/llvm-project/cfe/trunk@%CLANG_REV% clang
cd ..\..\llvm-build
set CC=cl
set CXX=cl
cmake -G Ninja ..\llvm -DCMAKE_BUILD_TYPE=Release -DLLVM_USE_CRT_RELEASE=MT ^
ninja clang-format
bin\clang-format.exe --version

Mac & Linux step-by-step:

# Check out.
export CLANG_REV=198831   # You must change this value (see above)
rm -rf llvm
rm -rf llvm-build
mkdir llvm
mkdir llvm-build
svn co http://llvm.org/svn/llvm-project/llvm/trunk@$CLANG_REV llvm
cd llvm/tools
svn co http://llvm.org/svn/llvm-project/cfe/trunk@$CLANG_REV clang
cd ../../llvm-build

# Option 1: with cmake
time caffeinate ninja clang-format
strip bin/clang-format

# (On Linux, to build with clang, which produces smaller binaries, add this to
# your cmake invocation.
# On Mac, the system compiler is already clang so it's not needed there.)
-DCMAKE_C_COMPILER=$PWD/../chrome/src/third_party/llvm-build/Release+Asserts/bin/clang -DCMAKE_CXX_COMPILER=$PWD/../chrome/src/third_party/llvm-build/Release+Asserts/bin/clang++

Platform specific notes:

  • Windows: Visual Studio 2013 only.
  • Linux: so far (as of January 2014) we‘ve just included a 64-bit binary. It’s important to disable threading, else clang-format will depend on libatomic.so.1 which doesn't exist on Precise.
  • Mac: Remember to set MACOSX_DEPLOYMENT_TARGET when building! If you get configure warnings, you may need to install XCode 5 and avoid a goma environment.

Upload each binary to google storage

Copy the binaries into your chromium checkout (under src/buildtools/(win|linux64|mac)/clang-format(.exe?)). For each binary, you‘ll need to run upload_to_google_storage.py according to the instructions in README.txt. This will upload the binary into a publicly accessible google storage bucket, and update .sha1 file in your Chrome checkout. You’ll check in the .sha1 file (but NOT the clang-format binary) into source control. In order to be able to upload, you'll need write permission to the bucket -- see the prerequisites.

Copy the helper scripts and update README.chromium

There are some auxiliary scripts that ought to be kept updated in lockstep with the clang-format binary. These get copied into third_party/clang_format/scripts in your Chromium checkout.

The README.chromium file ought to be updated with version and date info.

Upload a CL according to the following template

Update clang-format binaries and scripts for all platforms.

I followed these instructions:

The binaries were built at clang revision ####### on ####DATETIME####.


The change should always include new .sha1 files for each platform (we want to keep these in lockstep), should never include clang-format binaries directly. The change should always update README.chromium

clang-format binaries should weigh in at 1.5MB or less. Watch out for size regressions.