//build directory for GN-based projects

This project provides a work-in-progress standalone version of the toolchains and configs used by the Chromium project.

Supported platforms

The toolchains have been tested on the following platforms:

Windows (MSVC 2013/2015, Clang 3.8)
FreeBSD (GCC 5, Clang 3.7)
Linux (GCC 4.9, Clang 3.8)

The testsrc branch contains the test/example project used by the CI tests.

Reference

Basic variables

All variables described here are build args and can be overridden in the user's args.gn file.

`//build/config/BUILDCONFIG.gn`

(these variables are available everywhere)

is_debug (default: true): Enable/disable debugging options.
is_clang (default: false): Favor Clang over the platform default (GCC/MSVC).
is_official_build (default: !is_debug): Set to enable the official build level of optimization. This enables an additional level of optimization above release (!is_debug).
external (default: "//external"): Label of the external projects directory. By convention, all 3rd-party projects should end up in this directory, so they can depend on each other (e.g. $external/mysql_connector -> $external/zlib)

`//build/toolchain/clang.gni`

use_lld (default: false): Use the new LLD linker. This requires is_clang to be true.
clang_base_path (default: ""): The path of your Clang installation folder (without /bin). If you use Clang on Windows, you are required to set this, as the Clang installation isn't automatically detected.

`//build/toolchain/compiler_version.gni`

gcc_version (default: auto-detected): Version of the GCC compiler. Note: Auto-detection is toolchain-specific and happens only if GCC is the active compiler.
Format: major * 10000 + minor * 100 + patchlevel
clang_version (default: auto-detected): Version of the Clang compiler. Note: Auto-detection is toolchain-specific and happens only if Clang is the active compiler.
Format: major * 10000 + minor * 100 + patchlevel
msc_ver (default: auto-detected): Value of the _MSC_VER variable. See https://msdn.microsoft.com/en-us/library/b0084kay.aspx. Note: Auto-detection happens only when targeting Windows.
msc_full_ver (default: auto-detected): Value of the _MSC_FULL_VER variable. See https://msdn.microsoft.com/en-us/library/b0084kay.aspx. Note: Auto-detection happens only when targeting Windows.

Windows toolchain

`//build/toolchain/win/settings.gni`

visual_studio_version (default: 2013): The MSVC version to use.
visual_studio_path (default: auto-detected): The path of your MSVC installation. Autodetected based on visual_studio_version.
windows_sdk_path (default: auto-detected): Path of your Windows SDK installation.

POSIX toolchain

This is the default toolchain for POSIX operating systems, which is used for all POSIX systems that don't have special toolchains.

`//build/toolchain/posix/settings.gni`

gcc_cc (default: gcc): Path of the GCC C compiler executable. Does not have to be absolute.
gcc_cxx (default: g++): Path of the GCC C++ compiler executable. Does not have to be absolute.
clang_cc (default: clang): Path of the Clang C compiler executable. Does not have to be absolute. Note: If clang_base_path is set, the default will be clang_base_path/bin/clang.
clang_cxx (default: clang++): Path of the Clang C++ compiler executable. Does not have to be absolute. Note: If clang_base_path is set, the default will be clang_base_path/bin/clang++.

Mac toolchain

TODO: Mac builds are currently unsupported.

Android toolchain

`//build/toolchain/android/settings.gni`

android_ndk_root (default: "$external/android_tools/ndk"): Path of the Android NDK.
android_ndk_version (default: "r12b"): NDK Version string.
android_ndk_major_version (default: 12): NDK Major version.
android_sdk_root (default: "$external/android_tools/sdk"): Path of the Android SDK.
android_sdk_version (default: "24"): Android SDK version.
android_sdk_build_tools_version (default: "24.0.2"): Version of the Build Tools contained in the SDK.
android_libcpp_lib_dir (default: ""): Libc++ library directory. Override to use a custom libc++ binary.
use_order_profiling (default: false): Adds intrumentation to each function. Writes a file with the order that functions are called at startup.

Recommended workflow

Fork this repo and add it as a submodule/DEPS-entry to your project. This way you can modify every part of the //build directory while still being able to easily merge upstream changes (e.g. support for new GN features that you don't want to implement yourself.)

dyu / gn-build