Android makefile编写基础

首先来看一个简单的Android makefile,这个是我上篇文章写的，重新摘出来:

LOCAL_PATH:=$(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE_TAGS := eng
LOCAL_LDLIBS := -L$(SYSROOT)/usr/lib -llog
LOCAL_SRC_FILES:= \
		ppp.c

LOCAL_MODULE:= PPPreboot
include $(BUILD_EXECUTABLE)
#include $(BUILD_SHARED_LIBRARY)

下面对上面的语法进行解析:

LOCAL_PATH:=$(call my-dir) 					 定义了当前模块的相对路径
include $(CLEAR_VARS)      					 清空了当前的环境变量
LOCAL_MODULE_TAGS := eng   					 指定模块在eng模式下才进行编译
LOCAL_LDLIBS := -L$(SYSROOT)/usr/lib -llog   编译需要的库
LOCAL_SRC_FILES:ppp.c      				     编译所需要的目标源文件，一般都是当前目录下，或者依赖于其它目录下
LOCAL_MODULE:= PPPreboot   					 编译生成该目标的名称，也就是最终的可执行文件
include $(BUILD_EXECUTABLE)				     编译所生成的目标的文件格式 

其中:

my-dir在build/core/definitions.mk定义
CLEAR_VARS在build/core/config.mk定义

以下就是我之前写的源码，简单的功能。

#include <stdio.h>
#include <stdlib.h>
#include <android/log.h>
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, "keymatch", __VA_ARGS__)
int main(void)
{
    int i ;
    freopen("/dev/ttyMT0", "a", stdout);setbuf(stdout, NULL);
    freopen("/dev/ttyMT0", "a", stderr);setbuf(stderr, NULL);
    LOGD("YYX---->reboot system!!!!!!--->201612.1\n");
    system("reboot");
    return 0 ;
} 

makefile还有源码写完以后我们就可以进行编译了。
首先，需要source build/envsetup.sh  初始化参数和环境变量
接着lunch  对应的平台的版本

接着就拥有了mm、mmm等编译工具
然后对刚刚写的程序进行手动编译: mmm external/test/

编译成功信息如下:

PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=6.0
TARGET_PRODUCT=em_t8350_emmc
TARGET_BUILD_VARIANT=eng
TARGET_BUILD_TYPE=release
TARGET_BUILD_APPS=
TARGET_ARCH=arm
TARGET_ARCH_VARIANT=armv7-a-neon
TARGET_CPU_VARIANT=cortex-a7
TARGET_2ND_ARCH=
TARGET_2ND_ARCH_VARIANT=
TARGET_2ND_CPU_VARIANT=
HOST_ARCH=x86_64
HOST_OS=linux
HOST_OS_EXTRA=Linux-3.13.0-32-generic-x86_64-with-Ubuntu-14.04-trusty
HOST_BUILD_TYPE=release
BUILD_ID=MRA58K
OUT_DIR=out
============================================
PRODUCT_COPY_FILES frameworks/base/data/sounds/effects/ogg/camera_click.ogg:system/media/audio/ui/camera_click.ogg ignored.
PRODUCT_COPY_FILES device/pskyed/em_t8350_emmc/init.recovery.mt8127.rc:root/init.recovery.mt8127.rc ignored.
PRODUCT_COPY_FILES device/pskyed/em_t8350_emmc/handheld_core_hardware.xml:system/etc/permissions/handheld_core_hardware.xml ignored.
make: Entering directory `/mnt/sdb1/yangyx/MT8127_t8350_Debug_Camera_20161121/MT8127_M0_MP8_0407_for_t8350'
build/core/Makefile:614: warning: overriding commands for target `out/target/product/em_t8350_emmc/boot.img'
build/core/Makefile:39: warning: ignoring old commands for target `out/target/product/em_t8350_emmc/boot.img'
No private recovery resources for TARGET_DEVICE em_t8350_emmc
Import includes file: out/target/product/em_t8350_emmc/obj/EXECUTABLES/PPPreboot_intermediates/import_includes
target thumb C: PPPreboot <= external/test/ppp.c
target Executable: PPPreboot (out/target/product/em_t8350_emmc/obj/EXECUTABLES/PPPreboot_intermediates/LINKED/PPPreboot)
target Unpacked: PPPreboot (out/target/product/em_t8350_emmc/obj/EXECUTABLES/PPPreboot_intermediates/PACKED/PPPreboot)
target Symbolic: PPPreboot (out/target/product/em_t8350_emmc/symbols/system/bin/PPPreboot)
Export includes file: external/test/Android.mk -- out/target/product/em_t8350_emmc/obj/EXECUTABLES/PPPreboot_intermediates/export_includes
target Strip: PPPreboot (out/target/product/em_t8350_emmc/obj/EXECUTABLES/PPPreboot_intermediates/PPPreboot)
Install: out/target/product/em_t8350_emmc/system/bin/PPPreboot
make: Leaving directory `/mnt/sdb1/yangyx/MT8127_t8350_Debug_Camera_20161121/MT8127_M0_MP8_0407_for_t8350'

#### make completed successfully (2 seconds) ####

输出的文件就在out/target/product/em_t8350_emmc/system/bin/PPPreboot，用什么手段执行它都可以，就看你的需求了。