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Using Bazel on Windows

Bazel runs on 64 bit Windows 7 or higher. Known issues are marked with label "Windows" on GitHub issues.

Bazel is a native Windows binary. Run it from the Windows Command Prompt (cmd.exe) or from PowerShell.

Requirements

  • Python 2.7 or later.
  • msys2 shell.

    You also need to set the BAZEL_SH environment variable to point to bash.exe. For example in the Windows Command Prompt (cmd.exe):

    set BAZEL_SH=C:\msys64\usr\bin\bash.exe
    
  • Several msys2 packages.

    Run the following command in the msys2 shell to install them:

    pacman -Syuu git curl zip unzip
    
  • Java JDK 8.

    JDK 7 and 9 are not supported.

    If you downloaded a binary distribution of Bazel (see installing Bazel on Windows), the binary has JDK 8 embedded by default.

  • If you built Bazel from source: set the JAVA_HOME environment variable to the JDK's directory.

    For example in the Windows Command Prompt (cmd.exe):

    set JAVA_HOME=C:\Program Files\Java\jdk1.8.0_112
    

    This step is not required if you downloaded a binary distribution of Bazel or installed Bazel using Chocolatey. See installing Bazel on Windows.

Environment variables you set in the Windows Command Prompt (cmd.exe) are only set in that command prompt session. If you start a new cmd.exe, you need to set the variables again. To always set the variables when cmd.exe starts, you can add them to the User variables or System variables in the Control Panel > System Properties > Advanced > Environment Variables... dialog box.

Installation

See Install Bazel on Windows for installation instructions.

Using Bazel on Windows

The first time you build any target, Bazel auto-configures the location of Python and the Visual C++ compiler. If you need to auto-configure again, run bazel clean then build a target.

Build C++

To build C++ targets, you need:

  • The Visual C++ compiler.

    You can install it in one of the following ways:

  • The BAZEL_VS or BAZEL_VC environment variable.

    Bazel tries to locate the C++ compiler the first time you build any target. To tell Bazel where the compiler is, you can set one of the following environment variables:

    • BAZEL_VS storing the Visual Studio installation directory
    • BAZEL_VC storing the Visual C++ Build Tools installation directory

    Setting one of these variables is enough. For example:

    set BAZEL_VS=C:\Program Files (x86)\Microsoft Visual Studio 14.0
    

    or

    set BAZEL_VC=C:\Program Files (x86)\Microsoft Visual Studio\2017\BuildTools\VC
    
  • The Windows SDK.

    The Windows SDK contains header files and libraries you need when building Windows applications, including Bazel itself.

If everything is set up, you can build a C++ target now!

Try building a target from one of our sample projects:

C:\projects\bazel> bazel build //examples/cpp:hello-world

C:\projects\bazel> bazel-bin\examples\cpp\hello-world.exe

Build Java

There's no setup necessary.

On Windows, Bazel builds three output files for java_binary rules:

  • a .jar file
  • a shell script that can set up the environment for the JVM and run the binary
  • a .cmd file (a batch script) that can call Bash with the aforementioned shell script.

Try building a target from one of our sample projects:

C:\projects\bazel> bazel build //examples/java-native/src/main/java/com/example/myproject:hello-world

C:\projects\bazel> bazel-bin\examples\java-native\src\main\java\com\example\myproject\hello-world.cmd

Build Python

To build Python targets, you need:

  • The Python interpreter

    Both Python 2 and Python 3 are supported.

    To tell Bazel where Python is, you can use --python_path=<path/to/python>. For example:

    bazel build --python_path=C:/Python27/python.exe ...
    

    If --python_path is not specified, Bazel uses python.exe as the interpreter and the binary looks for it in $PATH during runtime. If it is not in $PATH(for example, when you use py_binary as an action's executable, Bazel will sanitize $PATH), then the execution will fail.

On Windows, Bazel builds two output files for py_binary rules:

  • a self-extracting zip file
  • a batch script that can execute the Python interpreter with the self-extracting zip file as the argument

You can either run the batch script (it has a .cmd extension) or you can run Python with the self-extracting zip file as the argument.

Try building a target from one of our sample projects:

C:\projects\bazel> bazel build //examples/py_native:bin

C:\projects\bazel> bazel-bin\examples\py_native\bin.cmd

C:\projects\bazel> python bazel-bin\examples\py_native\bin

If you are interested in details about how Bazel builds Python targets on Windows, check out this design doc.