As many Chromium developers are on Linux/Mac, cross-compiling Chromium for Windows targets facilitates development for Windows targets on non-Windows machines.
It‘s possible to build most parts of the codebase on a Linux or Mac host while targeting Windows. It’s also possible to run the locally-built binaries on swarming. This document describes how to set that up, and current restrictions.
What does not work:
js2gtest tests are omitted from the build (bug) Note that newer WebUI tests are not based on js2gtest (see migration progress at crbug.com/1457360) and are included in the build.All other targets build fine (including chrome, browser_tests, ...).
Uses of .asm files have been stubbed out. As a result, Crashpad cannot report crashes, and NaCl defaults to disabled and cannot be enabled in cross builds (.asm bug).
Tell gclient that you need Windows build dependencies by adding target_os = ['win'] to the end of your .gclient. (If you already have a target_os line in there, just add 'win' to the list.) e.g.
solutions = [
{
...
}
]
target_os = ['android', 'win']
gclient sync, follow instructions on screen.
gclient sync should automatically download the Windows SDK for you. If this fails with an error:
Please follow the instructions at https://chromium.googlesource.com/chromium/src/+/HEAD/docs/win_cross.md
then you may need to re-authenticate via (with your google.com account):
cd path/to/chrome/src # Follow instructions, enter 0 as project id. download_from_google_storage --config
gclient sync should now succeed. Skip ahead to the GN setup section.
After installing Microsoft's development tools, you can package your Windows SDK installation into a zip file by running the following on a Windows machine:
cd path/to/depot_tools/win_toolchain python package_from_installed.py <vs version> -w <win version>
where <vs version> and <win version> correspond respectively to the versions of Visual Studio (e.g. 2019) and of the Windows SDK (e.g. 10.0.19041.0) installed on the Windows machine. Note that if you didn't install the ARM64 components of the SDK as noted in the link above, you should add --noarm to the parameter list.
These commands create a zip file named <hash value>.zip. Then, to use the generated file in a Linux or Mac host, the following environment variables need to be set:
export DEPOT_TOOLS_WIN_TOOLCHAIN_BASE_URL=<base url> export GYP_MSVS_HASH_<toolchain hash>=<hash value>
<base url> is the path of the directory containing the zip file (note that specifying scheme file:// is not required).
<toolchain hash> is hardcoded in src/build/vs_toolchain.py and can be found by setting DEPOT_TOOLS_WIN_TOOLCHAIN_BASE_URL and running gclient sync:
gclient sync ... Running hooks: 17% (11/64) win_toolchain ________ running '/usr/bin/python src/build/vs_toolchain.py update --force' in <chromium dir> Windows toolchain out of date or doesn't exist, updating (Pro)... current_hashes: desired_hash: <toolchain hash>
Add
target_os = "win"
to your args.gn.
If you're building on an arm host (e.g. a Mac with an Apple Silicon chip), you very likely also want to add
target_cpu = "x64"
lest you build an arm64 chrome/win binary.
Then just build, e.g.
ninja -C out/gnwin base_unittests.exe
This should be supported by the default RBE (remote execution).
A convenient way to copy chrome over to a Windows box is to build the mini_installer target. Then, copy just mini_installer.exe over to the Windows box and run it to install the chrome you just built.
Note that the mini_installer doesn't include PDB files. PDB files are needed to correctly symbolize stack traces (or if you want to attach a debugger).
You can run the Windows binaries you built on swarming, like so:
tools/run-swarmed.py out/gnwin base_unittests -- [ --gtest_filter=... ]
See the contents of run-swarmed.py for how to do this manually.
The linux-win-cross-rel buildbot does 64-bit release cross builds, and also runs tests. You can look at it to get an idea of which tests pass in the cross build.