新建目录external/hello
mkdir external/hello
cd external/hello
新建hello.c
#include <stdio.h>
int main()
{
printf("Hello World!\n");
return 0;
}
新建Android.mk，编译bin文件
LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE_TAGS := optional
LOCAL_MODULE := hello
LOCAL_SRC_FILES := $(call all-subdir-c-files)
include $(BUILD_EXECUTABLE)
编译
mmm external/hello/
输出路径：
out/target/product/xxx/system/bin/hello
hello bin
修改Android.mk，编译so文件
写法一
LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE_TAGS := optional
LOCAL_MODULE := hello
LOCAL_SRC_FILES := $(call all-subdir-c-files)
include $(BUILD_SHARED_LIBRARY)
写法二
LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE_TAGS := optional
LOCAL_MODULE_CLASS := SHARED_LIBRARIES
LOCAL_MODULE_SUFFIX := .so
LOCAL_MODULE := hello
LOCAL_SRC_FILES := $(call all-subdir-c-files)
include $(BUILD_PREBUILT)
输出路径：
out/target/product/xxx/obj/lib/hello.so
hello.so
修改Android.mk，编译a文件
LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE_TAGS := optional
LOCAL_MODULE := hello
LOCAL_SRC_FILES := $(call all-subdir-c-files)
include $(BUILD_STATIC_LIBRARY)
输出路径：
out/target/product/xxx/obj/STATIC_LIBRARIES/hello_intermediates/hello.a
hello.a
报错
编译报错
No rule to make target `out/target/product/xxx/obj/lib/libc.so'
解：
先编译整个工程
make -j8
设置BUILD_PREBUILT编译报错
build/core/base_rules.mk:97: *** external/hello: LOCAL_MODULE_CLASS must contain exactly one word, not "". Stop.
解：
添加LOCAL_MODULE_CLASS 。
参考
例说如何编译android模块 - Eliot_shao的专栏 - CSDN博客
https://blog.csdn.net/eliot_shao/article/details/50441219
Android编译环境（转） - allenpettle - ITeye博客
https://allenshao.iteye.com/blog/616052
android编译系统makefile(Android.mk)写法 - 飞翔的熊猫 - 博客园
https://www.cnblogs.com/hesiming/archive/2011/03/15/1984444.html
