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Compiling Bazel from source

To build Bazel from source, you can do one of the following:

Build Bazel using Bazel

If you already have a Bazel binary, you can build Bazel from a GitHub checkout.

You will need:

  • A GitHub checkout of Bazel’s sources at the desired commit.

  • The Bazel version that was the latest when the commit was merged. (Other Bazel versions may work too, but are not guaranteed to.) You can either download this version from GitHub, or build it from source, or bootstrap it as described below.

  • The same prerequisites as for bootstrapping (JDK, C++ compiler, etc.)

Once you have a Bazel binary to build with and the source tree of Bazel, cd into the directory and run bazel build //src:bazel.

Build Bazel from scratch (bootstrapping)

You can also build Bazel from scratch, without using an existing Bazel binary.

1. Download Bazel's sources (distribution archive)

(This step is the same for all platforms.)

  1. Download bazel-<version>-dist.zip from GitHub, for example bazel-0.18.0-dist.zip.

    There is a single, architecture-independent distribution archive. There are no architecture-specific or OS-specific distribution archives.

    You have to use the distribution archive to bootstrap Bazel. You cannot use a source tree cloned from GitHub. (The distribution archive contains generated source files that are required for bootstrapping and are not part of the normal Git source tree.)

  2. Unpack the zip file somewhere on disk.

    We recommend to also verify the signature made by our release key 48457EE0.

To build a development version of Bazel from a GitHub checkout, you need a working Bazel binary. Scroll up to see how to build Bazel using Bazel.

2. Bootstrap Bazel on Ubuntu Linux, macOS, and other Unix-like systems

(Scroll down for instructions for Windows.)

2.1. Install the prerequisites

  • Bash

  • zip, unzip

  • C++ build toolchain

  • JDK 8. You must install version 8 of the JDK. Versions other than 8 are not supported.

  • Python. Versions 2 and 3 are supported, installing one of them is enough.

For example on Ubuntu Linux you can install these requirements using the following command:

sudo apt-get install build-essential openjdk-8-jdk python zip unzip

2.2. Bootstrap Bazel

  1. Open a shell or Terminal window.

  2. cd to the directory where you unpacked the distribution archive.

  3. Run the compilation script: bash ./compile.sh.

The compiled output is placed into output/bazel. This is a self-contained Bazel binary, without an embedded JDK. You can copy it anywhere or use it in-place. For convenience we recommend copying this binary to a directory that’s on your PATH (such as /usr/local/bin on Linux).

2. Bootstrap Bazel on Windows

(Scroll up for instructions for Linux, macOS, and other Unix-like systems.)

2.1. Install the prerequisites

  • MSYS2 shell

  • The MSYS2 packages for zip and unzip. Run the following command in the MSYS2 shell:

    pacman -Syu zip unzip
    
  • The Visual C++ compiler. Install the Visual C++ compiler either as part of Visual Studio 2015 or newer, or by installing the latest Build Tools for Visual Studio 2017.

  • JDK 8. You must install version 8 of the JDK. Versions other than 8 are not supported.

  • Python. Versions 2 and 3 are supported, installing one of them is enough. You need the Windows-native version (downloadable from https://www.python.org). Versions installed via pacman in MSYS2 will not work.

2.2. Bootstrap Bazel

  1. Open the MSYS2 shell.

  2. Set the following environment variables:
    • Either BAZEL_VS or BAZEL_VC (they are not the same): Set to the path to the Visual Studio directory (BAZEL_VS) or to the Visual C++ directory (BAZEL_VC). Setting one of them is enough.
    • BAZEL_SH: Path of the MSYS2 bash.exe. See the command in the examples below.

      Do not set this to C:\Windows\System32\bash.exe. (You have that file if you installed Windows Subsystem for Linux.) Bazel does not support this version of bash.exe.

    • PATH: Add the Python directory.
    • JAVA_HOME: Set to the JDK directory.

    Example (using BAZEL_VS):

    export BAZEL_VS="C:/Program Files (x86)/Microsoft Visual Studio/2017/BuildTools"
    export BAZEL_SH="$(cygpath -m $(realpath $(which bash)))"
    export PATH="/c/python27:$PATH"
    export JAVA_HOME="C:/Program Files/Java/jdk1.8.0_112"
    

    or (using BAZEL_VC):

    export BAZEL_VC="C:/Program Files (x86)/Microsoft Visual Studio/2017/BuildTools/VC"
    export BAZEL_SH="$(cygpath -m $(realpath $(which bash)))"
    export PATH="/c/python27:$PATH"
    export JAVA_HOME="C:/Program Files/Java/jdk1.8.0_112"
    
  3. cd to the directory where you unpacked the distribution archive.

  4. Run the compilation script: ./compile.sh

The compiled output is placed into output/bazel.exe. This is a self-contained Bazel binary, without an embedded JDK. You can copy it anywhere or use it in-place. For convenience we recommend copying this binary to a directory that’s on your PATH.

You don’t need to run Bazel from the MSYS2 shell. You can run Bazel from the Command Prompt (cmd.exe) or PowerShell.