pw_android_toolchain

Pigweed AI summary: The pw_android_toolchain module provides GN toolchains for building Pigweed against an Android NDK. The tool names and paths are derived from build args and defaults, and the Android NDK must be downloaded and its location specified using the pw_android_toolchain_NDK_PATH build arg. The module defines several toolchains for different architectures and optimization levels. Defining toolchains is similar to pw_toolchain, but with pw_generate_android_toolchain instead of generate_toolchain. The Android SDK target version defaults

Android toolchains differ from pw_toolchain in that the latter defines the tool names and paths at the lowest level, with customisation added at higher levels, while in pw_android_toolchain the tool names and paths are derived from build args and defaults so are defined last by calling pw_generate_android_toolchain.

Setup

Pigweed AI summary: To set up Pigweed, you need to download and unpack the Android NDK and specify its location using the build argument pw_android_toolchain_NDK_PATH. You can also configure Pigweed build options using gn args out.

You must first download and unpack a copy of the Android NDK and let Pigweed know where that is located using the pw_android_toolchain_NDK_PATH build arg.

You can set Pigweed build options using gn args out.

Toolchains

Pigweed AI summary: The "pw_android_toolchain" provides GN toolchains for building Pigweed against an Android NDK. The toolchains available include various options for different architectures and optimization levels. However, the documentation for this module is currently incomplete.

pw_android_toolchain provides GN toolchains that may be used to build Pigweed against an Android NDK. The following toolchains are defined:

• arm_android_debug

• arm_android_size_optimized

• arm_android_speed_optimized

• arm64_android_debug

• arm64_android_size_optimized

• arm64_android_speed_optimized

• x64_android_debug

• x64_android_size_optimized

• x64_android_speed_optimized

• x86_android_debug

• x86_android_size_optimized

• x86_android_speed_optimized

Note

The documentation for this module is currently incomplete.

Defining Toolchains

Pigweed AI summary: This section explains how to define Android NDK toolchains using the <literal>pw_generate_android_toolchain</literal> command and setting <literal>current_cpu</literal> in the toolchain <literal>defaults</literal>. It provides an example code snippet and mentions that <literal>pw_generate_android_toolchains</literal> does not require <literal>current_cpu</literal> to be set. The section also mentions how to customize the Android SDK target version by setting <literal>api_level

Defining Android NDK toolchains is similar to pw_toolchain except that instead of using generate_toolchain use pw_generate_android_toolchain, and ensure that current_cpu is set in the toolchain defaults.

For example:

import("//build_overrides/pigweed.gni")

import("$dir_pw_android_toolchain/toolchains.gni")
import("$dir_pw_android_toolchain/generate_toolchain.gni")

my_target_scope = {
  # Use Pigweed's Android toolchain as a base.
  _toolchain_base = pw_toolchain_android.debug

  # Forward everything except the defaults scope from that toolchain.
  forward_variables_from(_toolchain_base, "*", [ "defaults" ])

  defaults = {
    # Forward everything from the base toolchain's defaults.
    forward_variables_from(_toolchain_base.defaults, "*")

    # Build for 64-bit AArch64 Android devices.
    current_cpu = "arm64"

    # Extend with custom build arguments for the target.
    pw_log_BACKEND = dir_pw_log_tokenized
  }
}

# Create the actual GN toolchain from the scope.
pw_generate_android_toolchain("my_target") {
  forward_variables_from(my_target_scope, "*")
}

Since Android NDKs contain toolchains for all supported targets, as a convenience, pw_generate_android_toolchains does not require that current_cpu is set. If any toolchain scope in the list does not set it, a toolchain for each supported target will be generated.

# Generate arm_*, arm64_*, x64_*, and x86_* for each scope in the list.
pw_generate_android_toolchains("target_toolchains) {
  toolchains = pw_toolchain_android_list
}

Customization

Pigweed AI summary: This paragraph explains that the default target version for the Android SDK is determined by the build argument "pw_android_toolchain_API_LEVEL," but it can be overridden globally or on a per-toolchain level by setting the "api_level" in the toolchain defaults.

The Android SDK target version defaults to the value of the pw_android_toolchain_API_LEVEL build arg. You can override this on global level, or on a per-toolchain level by setting api_level in the toolchain defaults.