Documentation

Windows support is highly experimental. Known issues are marked with label "Windows" on github issues.

We currently support only 64 bit Windows 7 or higher and we compile Bazel as a msys2 binary.

Installation

See instructions on the installation page.

Requirements

Before you can compile or run Bazel, you will need to set some environment variables:

export JAVA_HOME="$(ls -d C:/Program\ Files/Java/jdk* | sort | tail -n 1)"
export BAZEL_SH=c:/tools/msys64/usr/bin/bash.exe

If you run outside of bash, ensure that msys-2.0.dll is in your PATH (if you install msys2 to c:\tools\msys64, just add c:\tools\msys64\usr\bin to PATH).

If you have another tool that vendors msys2 (such as msysgit), then c:\tools\msys64\usr\bin must appear in your PATH before entries for those tools.

Similarly, if you have bash on Ubuntu on Windows installed, you should make sure c:\tools\msys64\usr\bin appears in PATH before c:\windows\system32, because otherwise Windows' bash.exe is used before msys2's.

Use where msys-2.0.dll to ensure your PATH is set up correctly.

To run Bazel (even pre-built binaries), you will need:

  • Java JDK 8 or later
  • msys2 shell (need to be installed at C:\tools\msys64\).
    • We build against version 20160205, you will need this version in order to run the pre-built release Bazel binaries.
    • You can also use newer versions or the latest version, but then you will need to compile Bazel from the distribution archive (the source zip file) so that it's linked against the right version of msys-2.0.dll. See also the known issues.
  • Several msys2 packages. Use the pacman command to install them:

     pacman -Syuu gcc git curl zip unzip zlib-devel
    

To compile Bazel, in addition to the above you will need:

  • Visual C++ with Windows SDK installed (Community Edition is fine). Note: we intend to relax this requirement in the future to only require the Microsoft Visual C++ Build Tools, see github issue #2448.
  • You may need to apply some patches/workarounds, see the known issues.

Compiling Bazel on Windows

Ensure you have the requirements.

To build Bazel:

  • Open the msys2 shell.
  • Clone the Bazel git repository as normal.
  • Set the environment variables (see above)
  • Run compile.sh in Bazel directory.
  • If all works fine, bazel will be built at output\bazel.exe.

Using Bazel on Windows

Bazel now supports building C++, Java and Python targets on Windows.

Build C++

To build C++ targets, you will need:

  • Visual Studio
    We are using MSVC as the native C++ toolchain, so please ensure you have Visual Studio installed with the Visual C++ > Common Tools for Visual C++ and Visual C++ > Microsoft Foundation Classes for C++ features. (which is NOT the default installation type of Visual Studio). You can set BAZEL_VS environment variable to tell Bazel where Visual Studio is, otherwise Bazel will try to find the latest version installed.
    For example: export BAZEL_VS="C:/Program Files (x86)/Microsoft Visual Studio 14.0"

  • Python 2.7
    Currently, we use python wrapper scripts to call the actual MSVC compiler, so please make sure Python is installed and its location is added into PATH. It's also a good idea to set BAZEL_PYTHON environment variable to tell Bazel where python is.
    For example: export BAZEL_PYTHON=C:/Python27/python.exe

Bazel will auto-configure the location of Visual Studio and Python at the first time you build any target. If you need to auto-configure again, just run bazel clean then build a target.

If everything is set up, you can build C++ target now! However, since MSVC toolchain is not default on Windows yet, you should use flag --cpu=x64_windows_msvc to enable it like this:

$ bazel build --cpu=x64_windows_msvc examples/cpp:hello-world
$ ./bazel-bin/examples/cpp/hello-world.exe
$ bazel run --cpu=x64_windows_msvc examples/cpp:hello-world

Build Java

Building Java targets works well on Windows, no special configuration is needed. Just try:

$ bazel build examples/java-native/src/main/java/com/example/myproject:hello-world
$ ./bazel-bin/examples/java-native/src/main/java/com/example/myproject/hello-world
$ bazel run examples/java-native/src/main/java/com/example/myproject:hello-world

Build Python

On Windows, we build a self-extracting zip file for executable python targets, you can even use python ./bazel-bin/path/to/target to run it in native Windows command line (cmd.exe). See more details in this design doc.

$ bazel build examples/py_native:bin
$ ./bazel-bin/examples/py_native/bin
$ python ./bazel-bin/examples/py_native/bin    # This works in both msys and cmd.exe
$ bazel run examples/py_native:bin