android13/art/build/README.md

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# Building the ART Module
ART is built as a module in the form of an APEX package, `com.android.art.apex`.
That package can be installed with `adb install` on a device running Android S
or later. It is also included in the system partition (in the `system/apex`
directory) of platform releases, to ensure it is always available.
The recommended way to build the ART Module is to use the `master-art` manifest,
which only has the sources and dependencies required for the module.
Currently it is also possible to build ART directly from sources in a platform
build, i.e. as has been the traditional way up until Android S. However that
method is being phased out.
The ART Module is available as a debug variant, `com.android.art.debug.apex`,
which has extra internal consistency checks enabled, and some debug tools. A
device cannot have both the non-debug and debug variants installed at once - it
may not boot then.
`com.google.android.art.apex` (note `.google.`) is the Google signed variant of
the module. It is also mutually exclusive with the other ones.
## Building as a module on `master-art`
1. Check out the `master-art` tree:
```
repo init -b master-art -u <repository url>
```
See the [Android source access
instructions](https://source.android.com/setup/build/downloading) for
further details.
2. Set up the development environment:
```
banchan com.android.art <arch>
export SOONG_ALLOW_MISSING_DEPENDENCIES=true
```
For Google internal builds on the internal master-art branch, specify
instead the Google variant of the module and product:
```
banchan com.google.android.art mainline_modules_<arch>
export SOONG_ALLOW_MISSING_DEPENDENCIES=true
```
`<arch>` is the device architecture, one of `arm`, `arm64`, `x86`, or
`x86_64`. Regardless of the device architecture, the build also includes the
usual host architectures, and 64/32-bit multilib for the 64-bit products.
To build the debug variant of the module, specify `com.android.art.debug`
instead of `com.android.art`. It is also possible to list both.
3. Build the module:
```
m apps_only dist
```
4. Install the module and reboot:
```
adb install out/dist/com.android.art.apex
adb reboot
```
The name of the APEX file depends on what you passed to `banchan`.
## Building as part of the base system image
NOTE: This method of building is slated to be obsoleted in favor of the
module build on `master-art` above (b/172480617).
1. Check out a full Android platform tree and lunch the appropriate product the
normal way.
2. Ensure the ART Module is built from source:
```
export ART_MODULE_BUILD_FROM_SOURCE=true
```
If this isn't set then the build may use prebuilts of the ART Module that
may be older than the sources.
3. Build the system image the normal way, for example:
```
m droid
```
## Prebuilts
Prebuilts are used for the ART Module dependencies that have sources outside the
`master-art` manifest. Conversely the ART Module may be a prebuilt when used in
platform builds of the base system image.
The locations of the prebuilts are:
* `prebuilts/runtime/mainline` for prebuilts and SDKs required to build the ART
Module.
See
[prebuilts/runtime/mainline/README.md](https://android.googlesource.com/platform/prebuilts/runtime/+/master/mainline/README.md)
for instructions on how to update them.
* `packages/modules/ArtPrebuilt` for the ART Module APEX packages, if present.
* `prebuilts/module_sdk/art` for the ART Module SDK and other tools, needed to
build platform images and other modules that depend on the ART Module.