1- adroid 演进过程

Android编译演进过程：

Android7.0之前 使用GNU Make

Android7.0 引入ninja、kati、Android.bp和soong构建系统

Android8.0 默认打开Android.bp

Android9.0 强制使用Android.bp

Make 构建系统得到了广泛的支持和使用，但在 Android 层面变得缓慢、容易出错、无法扩展且难以测试。Soong 构建系统正好提供了 Android build 所需的灵活性。

2- android build 流程

build/ 目录下

blueprint：用于处理Android.bp，编译生成*.ninja文件，用于做ninja的处理

kati：用于处理Android.mk，编译生成*.ninja文件，用于做ninja的处理

make：文件夹还是原始的make那一套流程，比如envsetup.sh

soong：构建系统，核心编译为soong_ui.bash

build 流程

3 编译环境初始化

source build/envsetup.sh

输入指令hmm 就可以查看信息

Run "m help" for help with the build system itself.

Invoke ". build/envsetup.sh" from your shell to add the following functions to your environment:

- lunch: lunch -

Selects as the product to build, and as the variant to

build, and stores those selections in the environment to be read by subsequent

invocations of 'm' etc.

- tapas: tapas [ ...] [arm|x86|mips|arm64|x86_64|mips64] [eng|userdebug|user]

- croot: Changes directory to the top of the tree, or a subdirectory thereof.

- m: Makes from the top of the tree.

- mm: Builds all of the modules in the current directory, but not their dependencies.

- mmm: Builds all of the modules in the supplied directories, but not their dependencies.

To limit the modules being built use the syntax: mmm dir/:target1,target2.

- mma: Builds all of the modules in the current directory, and their dependencies.

- mmma: Builds all of the modules in the supplied directories, and their dependencies.

- provision: Flash device with all required partitions. Options will be passed on to fastboot.

- cgrep: Greps on all local C/C++ files.

- ggrep: Greps on all local Gradle files.

- jgrep: Greps on all local Java files.

- resgrep: Greps on all local res/*.xml files.

- mangrep: Greps on all local AndroidManifest.xml files.

- mgrep: Greps on all local Makefiles files.

- sepgrep: Greps on all local sepolicy files.

- sgrep: Greps on all local source files.

- godir: Go to the directory containing a file.

- allmod: List all modules.

- gomod: Go to the directory containing a module.

- pathmod: Get the directory containing a module.

- refreshmod: Refresh list of modules for allmod/gomod.

Environment options:

- SANITIZE_HOST: Set to 'true' to use ASAN for all host modules. Note that

ASAN_OPTIONS=detect_leaks=0 will be set by default until the

build is leak-check clean.

- ANDROID_QUIET_BUILD: set to 'true' to display only the essential messages.

lunch 2

PLATFORM_VERSION_CODENAME=REL

PLATFORM_VERSION=10

TARGET_PRODUCT=aosp_arm64

TARGET_BUILD_VARIANT=eng

TARGET_BUILD_TYPE=release

TARGET_ARCH=arm64

TARGET_ARCH_VARIANT=armv8-a

TARGET_CPU_VARIANT=generic

TARGET_2ND_ARCH=arm

TARGET_2ND_ARCH_VARIANT=armv8-a

TARGET_2ND_CPU_VARIANT=generic

HOST_ARCH=x86_64

HOST_2ND_ARCH=x86

HOST_OS=linux

HOST_OS_EXTRA=Linux-4.15.0-137-generic-x86_64-Ubuntu-16.04.7-LTS

HOST_CROSS_OS=windows

HOST_CROSS_ARCH=x86

HOST_CROSS_2ND_ARCH=x86_64

HOST_BUILD_TYPE=release

BUILD_ID=QD4A.200805.003

OUT_DIR=out

4-make 说明

通过soong执行编译构建，这里执行make命令时，main.mk文件把一些环境变量和目标都配置好后，会执行envsetup.sh中的make()进行编译。

function make()

{

_wrap_build $(get_make_command "$@") "$@"

}

function get_make_command()

{

# If we're in the top of an Android tree, use soong_ui.bash instead of make

if [ -f build/soong/soong_ui.bash ]; then

# Always use the real make if -C is passed in

for arg in "$@"; do

if [[ $arg == -C* ]]; then

echo command make

return

fi

done

echo build/soong/soong_ui.bash --make-mode

else

echo command make

fi

}

build/soong/soong_ui.bash --make-mode

------->

[build/soong/soong_ui.bash] -------》 下面说明

# Save the current PWD for use in soong_ui

export ORIGINAL_PWD=${PWD}

export TOP=$(gettop)

source ${TOP}/build/soong/scripts/microfactory.bash

soong_build_go soong_ui android/soong/cmd/soong_ui -->生成soog_ui

cd ${TOP} --->return root

exec "$(getoutdir)/soong_ui" "$@"------>exec out/soong_ui --make-mode build

“echo build/soong/soong_ui.bash --make-mode ”

soong的编译过程:

soong_ui.bash 调用流程：

可以看到include 了main.mk文件，从main.mk开始，将通过include命令将其所有需要的.mk文件包含进来，最终在内存中形成一个包括所有编译脚本的集合，这个相当于一个巨大Makefile文件。Makefile文件看上去很庞大，其实主要由三种内容构成: 变量定义、函数定义和目标依赖规则，此外mk文件之间的包含也很重要。

文件

作用

build/make/core/main.mk

Build的主控文件，主要作用是包含其他mk，以及定义几个最重要的编译目标，同时检查编译工具的版本，例如如gcc、clang、java等

build/make/core/config.mk

Build的配置文件，主要是区分各个产品的配置，并将这些编译器参数引入产品配置 BoardConfig.mk,同时也配置了一些编译器的路径等

build/make/core/definitions.mk

最重要的 Make 文件之一，在其中定义了大量的函数。这些函数都是 Build 系统的其他文件将用到的。例如：my-dir，all-subdir-makefiles，find-subdir-files，sign-package 等，关于这些函数的说明请参见每个函数的代码注释。

build/make/core/dex_preopt.mk

定义了dex优化相关的路径和参数

5.工具链的关系

Android.bp --> Blueprint --> Soong --> Ninja

Makefile or Android.mk --> kati --> Ninja

(Android.mk --> Soong --> Blueprint --> Android.bp)