Improve support for frameworks in gn

Add "frameworks" and "framework_dirs" variables to targets and configs
that are propagated using the following rules:

-   "frameworks" is propagated to all linkable targets (executables,
    shared libraries and complete static libraries)

-   "framework_dirs" is propagated to direct compile dependencies as
    "include_dirs" and also to all linkable targets (executables,
    shared libraries and complete static libraries)

The non-conventional propagation rules for "framework_dirs" is there
to support how framework are used on Apple's platforms (macOS & iOS).
A framework bundle is a way to ship a shared library with its public
headers, so the path to the framework needs to be propagated to the
compiler (to resolve import statement for the framework's header) and
to the linker (to find the path to the shared library contained in the
framework).

Add target of type CREATE_BUNDLE that generate a framework (identified
by the product type "com.apple.product-type.framework") as inherited
libraries since they contains shared library and add them to the list
of implicit dependencies to force the regeneration of linkable targets
if any of the framework API changes (this is bit pessimistic since it
can force an unnecessary rebuild if the linkable target does not link
with the framework, but this should be rare).

Bug: crbug.com/gn/119, crbug.com/1037607
Change-Id: Icef50c38ac02afab71f2348fe3f73b6124a29112
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/6660
Commit-Queue: Brett Wilson <brettw@chromium.org>
Reviewed-by: Brett Wilson <brettw@chromium.org>
29 files changed
tree: 9e58c1798f3ac84cf96de3c0068e8789b762ac02
  1. .clang-format
  2. .editorconfig
  3. .gitignore
  4. .style.yapf
  5. AUTHORS
  6. LICENSE
  7. OWNERS
  8. README.md
  9. build/
  10. docs/
  11. examples/
  12. infra/
  13. misc/
  14. src/
README.md

GN

GN is a meta-build system that generates build files for Ninja.

Related resources:

Getting a binary

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.

Examples

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:

Reporting bugs

If you find a bug, you can see if it is known or report it in the bug database.

Sending patches

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’).

Community

You may ask questions and follow along with GN‘s development on Chromium’s gn-dev@ Google Group.