docs/Building.md

# Building the NDK

The latest version of this document is available at
https://android.googlesource.com/platform/ndk/+/master/docs/Building.md.

Both Linux and Windows NDKs are built on Linux machines. Windows host binaries
are cross-compiled with MinGW.

Building the NDK for Mac OS X requires at least 10.13.

## Prerequisites

* [AOSP NDK Repository](http://source.android.com/source/downloading.html)
    * Check out the branch `master-ndk`. Do this in a new directory.

        ```bash
        repo init -u https://android.googlesource.com/platform/manifest \
            -b master-ndk

        # Googlers, follow http://go/repo-init/master-ndk (check the box for
        # AOSP, uncheck the box for the git superproject). At time of writing,
        # the correct invocation is:
        repo init -u \
            sso://android.git.corp.google.com/platform/manifest -b master-ndk
        ```

If you wish to rebuild a given release of the NDK, the release branches can also
be checked out. They're named `ndk-release-r${RELEASE}` for newer releases, but
`ndk-r{RELEASE}-release` for older releases. For example, to check out the r19
release branch, use the `-b ndk-release-r19` flag instad of `-b master-ndk`.

Linux dependencies are listed in the [Dockerfile]. You can use docker to build
the NDK:

```bash
docker build -t ndk-dev infra/docker
docker run -it -u $UID -v `realpath ..`:/src -w /src/ndk ndk-dev ./checkbuild.py
```

Building on Mac OS X has similar dependencies as Linux, but also requires Xcode.

Running tests requires that `adb` is in your `PATH`. This is provided as part of
the [Android SDK].

[Dockerfile]: ../infra/docker/Dockerfile
[Android SDK]: https://developer.android.com/studio/index.html#downloads

## Build

### For Linux or Darwin

```bash
$ python checkbuild.py
```

### For Windows, from Linux

```bash
$ python checkbuild.py --system windows64
```

`checkbuild.py` will also build all of the NDK tests. This takes about 3x as
long as building the NDK itself, so pass `--no-build-tests` to skip building the
tests if you're iterating on build behavior or plan to rebuild only specific
tests. Tests can be built later with `python run_tests.py --rebuild`.

Note: The NDK's build and test scripts are implemented in Python 3 (currently
3.9). `checkbuild.py` will use a prebuilt Python, but `run_tests.py` does not do
this yet. `run_tests.py` also can be run outside of a complete development
environment (as it is when it is run on Windows), so a Python 3.9 virtualenv is
recommended.

## Packaging

Packaging uses `zip -9` so is extremely time consuming and disabled by default.
Use the `--package` flag to force packaging locally. This is not required for
local development and only needs to be used when testing packaging behavior.