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Compiling Bazel from Source (bootstrapping)

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

  • Build it using an existing Bazel Binary

  • Build it without an existing Bazel binary, which is known as bootstraping

This document describes how to bootstrap Bazel.

1. Install the prerequisites

Ubuntu Linux, macOS, and other Unix-like systems

Ensure you have installed:

  • 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.

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

Windows

Ensure you have installed:

  • MSYS2 shell

  • The required MSYS2 packages. 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. You need the Windows-native version (downloadable from https://www.python.org). Versions installed via pacman in MSYS2 will not work.

2. Download and unpack Bazel's source files (distribution archive)

Download bazel-<version>-dist.zip from GitHub (for example, bazel-0.15.2-dist.zip). If you want to build a development snapshot of Bazel, download the archive for the latest release before the snapshot you are interested in as you need to bootstrap that version of Bazel first in order to build the snapshot version.

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

Note: You have to use the distribution archive to build Bazel from source. 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.)

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

3. Bootstrap Bazel

Ubuntu Linux, macOS, and other Unix-like systems

  1. Open a shell or Terminal window.

  2. Change into 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 to a directory in the PATH variable (such as /usr/local/bin on Linux) or use it in-place.

Windows

  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.

    For 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. Change into 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 to a directory within the %PATH% variable or use it in-place.

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

4. Development snapshots of Bazel

Once you have a reasonably new working bazel binary, you can also build snapshot versions of Bazel by checking out the commit you're interested in and build a new version of Bazel by bazel build //src:bazel.