# Introduction

The Dart VM runs on a variety of ARM processors on Linux and Android. This document explains how to build the Dart VM and SDK to target these platforms.

> **Note**: You must follow the steps in [Building.md](Building.md) to set up the environment and properly fetch the source code. Cloning the repository or obtaining the source code through other means will not result in a successful build.

# Cross-compiling

The build scripts download a Clang toolchain that can target X64, ARM, ARM64 or RISCV64 and run on an X64 or ARM64 host. For these cases, you do not need to install a cross-compiler yourself. For other cases, like building on a RISCV64 host or targeting RISCV32, you will need to manually install a toolchain.

## Linux

If you are running Debian/Ubuntu, you can obtain a cross-compiler by doing the following:	

```bash
$ sudo apt-get install g++-x86-64-linux-gnu     # To target x64
$ sudo apt-get install g++-arm-linux-gnueabihf  # To target arm
$ sudo apt-get install g++-aarch64-linux-gnu    # To target arm64
$ sudo apt-get install g++-riscv64-linux-gnu    # To target riscv64
```

## Android

Follow instructions under ["One-time Setup" under Android](https://github.com/dart-lang/sdk/blob/main/docs/Building-the-Dart-VM-for-Android.md)

# Building

## Linux

With the default Debian/Ubuntu toolchains, simply do:

```bash
$ ./tools/build.py --no-clang --mode release --arch arm create_sdk
$ ./tools/build.py --no-clang --mode release --arch arm64 create_sdk
$ ./tools/build.py --no-clang --mode release --arch riscv64 create_sdk
```

You can also produce only a Dart VM runtime, no SDK, by replacing `create_sdk` with `runtime`. This process involves also building a VM that targets x64, which is used to generate a few parts of the SDK.

You can use a different toolchain using the -t switch. For example, if the path to your gcc is /path/to/toolchain/prefix-gcc, then you'd invoke the build script with:

```bash
$ ./tools/build.py --no-clang -m release -a arm -t arm=/path/to/toolchain/prefix create_sdk
$ ./tools/build.py --no-clang -m release -a arm64 -t arm64=/path/to/toolchain/prefix create_sdk
$ ./tools/build.py --no-clang -m release -a riscv32 -t riscv32=/path/to/toolchain/prefix create_sdk
$ ./tools/build.py --no-clang -m release -a riscv64 -t riscv64=/path/to/toolchain/prefix create_sdk
```

## Android

The standalone Dart VM can also target Android.

```
$ ./tools/build.py --mode=release --arch=arm --os=android create_sdk
$ ./tools/build.py --mode=release --arch=arm64 --os=android create_sdk
$ ./tools/build.py --mode=release --arch=riscv64 --os=android create_sdk
```

## Debian Packages

You can create Debian packages targeting ARM or RISC-V as follows:

```
$ ./tools/build.py --mode=release --arch=arm,arm64,riscv64 debian_package
```

# Testing

In addition to cross-compiling the Dart SDK, tests can be run even without the corresponding hardware by using QEMU.

```bash
$ sudo apt install qemu-user libc6-armhf-cross libc6-arm64-cross libc6-riscv64-cross
$ ./tools/build.py --mode release --arch arm,arm64,riscv64 runtime
$ ./tools/test.py --mode release --arch arm,arm64,riscv64 --use-qemu lib
```