| commit | 6966efb0f6ff0f80b1a6bc5ee6ac2f343ecf3523 | [log] [tgz] |
|---|---|---|
| author | RJ Ascani <rjascani@google.com> | Mon Oct 19 16:50:11 2020 -0700 |
| committer | Commit Bot <commit-bot@chromium.org> | Fri Dec 11 17:17:17 2020 +0000 |
| tree | f094107d1e05a2a0648ca1db3bfd66ba0e5a97bb | |
| parent | 2d9fd62c6572e324ae893e2c5bc2f054b7f70fa4 [diff] |
Restat build.ninja after gen As of version 1.8, ninja caches mtimes in the .ninja_log file and will not restat a file if it has an entry in the .ninja_log. This becomes problematic for generator files such as build.ninja. In a scenario where the .ninja_log has an entry for build.ninja (ie, after ninja has had to trigger a re-gen) and a manual run of of `gn gen` has updated the build.ninja file, a subsequent invocation of ninja will trigger yet another re-gen of build.ninja. This can be reproduced like this: # Initial build gn gen out && ninja -C out # Trigger ninja re-gen so there's a build.ninja log entry touch BUILD.gn && ninja -C out # Manual re-gen gn gen out # The following command will re-gen again before building ninja -C out To work around this, the recommended approach from ninja is to use the ninja restat tool to get ninja to update the mtime in the .ninja_log. This CL does that by attempting to invoke `ninja -t restat build.ninja` immediately after the build.ninja is generated by `gn gen`. Because this tool was only introduced in 1.10, the usage is gated on having a ninja binary of at least that version. The ninja binary can be provided via the --ninja-executable switch. Bug: 136 Change-Id: If40391aa13e6ef71c4e8ab26aff57d66a8137b8e Reviewed-on: https://gn-review.googlesource.com/c/gn/+/10400 Commit-Queue: RJ Ascani <rjascani@google.com> Reviewed-by: Brett Wilson <brettw@chromium.org>
GN is a meta-build system that generates build files for Ninja.
Related resources:
You can download the latest version of GN binary for Linux, macOS and Windows.
Alternatively, you can build GN from source:
git clone https://gn.googlesource.com/gn cd gn python build/gen.py ninja -C out # To run tests: out/gn_unittests
On Windows, it is expected that cl.exe, link.exe, and lib.exe can be found in PATH, so you'll want to run from a Visual Studio command prompt, or similar.
On Linux and Mac, the default compiler is clang++, a recent version is expected to be found in PATH. This can be overridden by setting CC, CXX, and AR.
There is a simple example in examples/simple_build directory that is a good place to get started with the minimal configuration.
To build and run the simple example with the default gcc compiler:
cd examples/simple_build ../../out/gn gen -C out ninja -C out ./out/hello
For a maximal configuration see the Chromium setup:
and the Fuchsia setup:
If you find a bug, you can see if it is known or report it in the bug database.
GN uses Gerrit for code review. The short version of how to patch is:
Register at https://gn-review.googlesource.com. ... edit code ... ninja -C out && out/gn_unittests
Then, to upload a change for review:
git commit git push origin HEAD:refs/for/master
The first time you do this you'll get an error from the server about a missing change-ID. Follow the directions in the error message to install the change-ID hook and run git commit --amend to apply the hook to the current commit.
When revising a change, use:
git commit --amend git push origin HEAD:refs/for/master
which will add the new changes to the existing code review, rather than creating a new one.
We ask that all contributors sign Google's Contributor License Agreement (either individual or corporate as appropriate, select ‘any other Google project’).
You may ask questions and follow along with GN‘s development on Chromium’s gn-dev@ Google Group.