1Using rules_go on Windows 2========================= 3 4.. _--incompatible_enable_cc_toolchain_resolution: https://github.com/bazelbuild/bazel/issues/7260 5.. _Installing Bazel on Windows: https://docs.bazel.build/versions/master/install-windows.html 6 7This document provides a list of instructions for setting up Bazel to build 8Go code on a Windows computer. 9 10Most of the difficulty here is installing a compatible C/C++ toolchain. Cgo 11only works with GCC and clang toolchains, so MSVC cannot be used. This is a 12Go limitation, not a Bazel or rules_go problem: cgo determines types of 13definitions by parsing error messages that GCC emits when compiling generated 14files. 15 16See also `Installing Bazel on Windows`_, the official instructions for 17installing Bazel. 18 19Install and configure dependencies 20---------------------------------- 21 22* Install msys2 from https://www.msys2.org/. This is needed to provide a bash 23 environment for Bazel. 24 25 * Follow the installation directions to the end, including 26 running ``pacman -Syu`` and ``pacman -Su`` in the msys2 shell. 27 28* Install additional msys2 tools. 29 30 * Run ``pacman -S mingw-w64-x86_64-gcc``. GCC is needed if you plan to build 31 any cgo code. MSVC will not work with cgo. This is a Go limitation, not a 32 Bazel limitation. cgo determines types of definitions by compiling specially 33 crafted C files and parsing error messages. GCC or clang are specifically 34 needed for this. 35 * Run ``pacman -S patch``. ``patch`` is needed by ``git_repository`` and 36 ``http_archive`` dependencies declared by rules_go. We use it to add 37 and modify build files. 38 39* Add ``C:\msys64\usr\bin`` to ``PATH`` in order to locate ``patch`` and 40 other DLLs. 41* Add ``C:\msys64\mingw64\bin`` to ``PATH`` in order to locate mingw DLLs. 42 ``protoc`` and other host binaries will not run without these. 43* Set the environment variable ``BAZEL_SH`` to ``C:\msys64\usr\bin\bash.exe``. 44 Bazel needs this to run shell scripts. 45* Set the environment variable ``CC`` to ``C:\msys64\mingw64\bin\gcc.exe``. 46 Bazel uses this to configure the C/C++ toolchain. 47* Install the MSVC++ redistributable from 48 https://www.microsoft.com/en-us/download/details.aspx?id=48145. 49 Bazel itself depends on this. 50* Install Git from https://git-scm.com/download/win. The Git install should 51 add the installed directory to your ``PATH`` automatically. 52 53Install bazel 54------------- 55 56* Download Bazel from https://github.com/bazelbuild/bazel/releases. 57* Move the binary to ``%APPDATA%\bin\bazel.exe``. 58* Add that directory to ``PATH``. 59* Confirm ``bazel version`` works. 60 61Confirm C/C++ works 62------------------- 63 64Create a workspace with a simple ``cc_binary`` target. 65 66.. code:: 67 68 -- WORKSPACE -- 69 70 -- BUILD.bazel -- 71 cc_binary( 72 name = "hello", 73 srcs = ["hello.c"], 74 ) 75 76 -- hello.c -- 77 #include <stdio.h> 78 79 int main() { 80 printf("hello\n"); 81 return 0; 82 } 83 84To build with MinGW, run the command below. Add the ``-s`` flag to print 85commands executed by Bazel to confirm MinGW is actually used. 86 87.. code:: 88 89 bazel build --cpu=x64_windows --compiler=mingw-gcc //:hello 90 91Future versions of Bazel will select a C/C++ toolchain using the same platform 92and toolchain system used by other rules. This will be the default after the 93`--incompatible_enable_cc_toolchain_resolution`_ flag is flipped. To ensure 94that the MinGW toolchain is registered, either build against a ``platform`` 95target with the ``@bazel_tools//tools/cpp:mingw`` constraint such as 96``@io_bazel_rules_go//go/toolchain:windows_amd64_cgo``, or define your own 97target explicitly, as below: 98 99.. code:: 100 101 platform( 102 name = "windows_amd64_mingw", 103 constraint_values = [ 104 "@bazel_tools//tools/cpp:mingw", 105 "@platforms//cpu:x86_64", 106 "@platforms//os:windows", 107 ], 108 ) 109 110You can build with the command below. This also ensures the MinGW toolchain is 111registered (it is not, by default). 112 113.. code:: 114 115 bazel build --extra_toolchains=@local_config_cc//:cc-toolchain-x64_windows_mingw --host_platform=//:windows_amd64_mingw --platforms=//:windows_amd64_mingw --incompatible_enable_cc_toolchain_resolution //:hello 116 117You may want to add these flags to a ``.bazelrc`` file in your project root 118directory or in your home directory. 119 120.. code:: 121 122 build --cpu=x64_windows 123 build --compiler=mingw-gcc 124 build --extra_toolchains=@local_config_cc//:cc-toolchain-x64_windows_mingw 125 build --host_platform=//:windows_amd64_mingw 126 build --platforms=//:windows_amd64_mingw 127 build --incompatible_enable_cc_toolchain_resolution 128 129Confirm Go works 130---------------- 131 132* Copy boilerplate from rules_go. 133* Confirm that you can run a pure Go "hello world" binary with 134 ``bazel run //:target`` 135* Confirm you can run a cgo binary with the same set of flags and platforms 136 used to build a C target above. 137