编译C/C++

前面我们完成了java的编译，编译成jar包，编译成apk。

接下来我们看看C/C++的编译，编译成静态库/动态库，编译成可执行文件。

静态库和动态库（共享库）的说明在前面已经和大家讲了。

编译so库

先给大家表演编译so库，后面的编译可执行程序时，我们可以依赖so库，这样子比较全。

所以就先学习一下如何编译库吧。

库也一样，我们分动态库和静态库。

先写个库吧，我写个简单的，比如说log输出。

头文件：log.h

#define TAG "SOB-LOG"
#include <string>
using namespace std;
namespace sob{
    void log(const string msg);
}

c++文件log.cpp

#include <iostream>
#include <string>
#include "log.h"

using namespace std;
namespace sob {
    void log(const string msg)
    {
        cout << TAG << " : " << msg << endl;
    }
}

就这么简单，现在，我们把它编译成共享库

编写Android.mk文件

还记得前面我们的Android.mk的结构吗？

image

于是，我们的脚本这样写了：

LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)

#放到vender目录下
LOCAL_VENDOR_MODULE = true
LOCAL_MODULE_TAGS := optional

LOCAL_MODULE:= liblog

LOCAL_C_INCLUDES := external/libcxx/include

LOCAL_SHARED_LIBRARIES := \
    libc++

LOCAL_SRC_FILES:= \
    log.cpp

include $(BUILD_SHARED_LIBRARY)

编译结果

hdc@ubuntu:~/Android5.1/packages/apps/HardwearTest/loglib$ mm
make: Entering directory '/home/hdc/Android5.1'
============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=5.1
TARGET_PRODUCT=aosp_x86
TARGET_BUILD_VARIANT=eng
TARGET_BUILD_TYPE=release
TARGET_BUILD_APPS=
TARGET_ARCH=x86
TARGET_ARCH_VARIANT=x86
TARGET_CPU_VARIANT=
TARGET_2ND_ARCH=
TARGET_2ND_ARCH_VARIANT=
TARGET_2ND_CPU_VARIANT=
HOST_ARCH=x86_64
HOST_OS=linux
HOST_OS_EXTRA=Linux-5.11.0-40-generic-x86_64-with-Ubuntu-20.04-focal
HOST_BUILD_TYPE=release
BUILD_ID=LMY47D
OUT_DIR=out
============================================
make: Circular out/target/product/generic_x86/obj/SHARED_LIBRARIES/liblog_intermediates/LINKED/liblog.so <- out/target/product/generic_x86/obj/lib/liblog.so dependency dropped.
make: Circular out/target/product/generic_x86/system/lib/liblog.so <- out/target/product/generic_x86/system/lib/liblog.so dependency dropped.
make: Nothing to be done for 'all_modules'.
make: Leaving directory '/home/hdc/Android5.1'

#### make completed successfully (1 seconds) ####

hdc@ubuntu:~/Android5.1/packages/apps/HardwearTest/loglib$

也就是在这个out/target/product/generic_x86/system/lib/liblog.so目录下有生成。

接下来我们编译一下可执行文件，然后依赖我们的log库。

编译成可执行文件

比如说最近写的一个程序，去查询是否有GSensor的，当然，这个是模拟器，就不是真的能测试，只是模拟给大家看如何编译一个可执行程序。

#include "loglib/log.h"
#include <string>

using namespace std;
using namespace sob;

void printHelp(void)
{
    log("帮助内容：");
    log("checkGyroscope 检查是否支持陀螺仪，1表示支持，-1表示不支持");
    log("getGsensorType 检查是否支持重力传感器，0-不支持，1-QMA7981，2-SC7A21，3-DA217");
    log("使用示例：hardwaretest checkGyroscope");
}

void handleCmd(char* cmd)
{
    //对命令进行判断和执行
    log("参数内容:");
    string cmdStr;
    cmdStr = cmd;

    //log("cmdStr ==> "+ cmdStr);
    if("checkGyroscope"==cmdStr)
    {
        log("测试是否有陀螺仪");
        //TODO:去检查是否有陀螺仪
    }else if("getGsensorType"==cmdStr)
    {
        log("检查重力传感器的类型");
        //TODO:去检查是否有重力传感器
    }else
    {
        printHelp();
    }
}

//argc是参数个数,argv[]是参数内容
int main(int argc, char *argv[]){
    log("do hardware test...");
    int i = 0;
    for(;i<argc;i++)
    {
        if(argc==1)
        {
            //打开帮助
            printHelp();
        }
        if(i>0){
            handleCmd(argv[i]);
        }
    }
}

按前面的套路，我们这样写Android.mk

LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)

# 编译出来的名称
LOCAL_MODULE := hardweartest

#源代码
LOCAL_SRC_FILES := \
    hardwaretest.cpp

#添加头部依赖
LOCAL_C_INCLUDES := external/libcxx/include

#添加依赖库
LOCAL_SHARED_LIBRARIES := \
    liblog \
    libc \
    libc++

include $(BUILD_EXECUTABLE)

编译结果：

hdc@ubuntu:~/Android5.1/packages/apps/HardwearTest$ mm
make: Entering directory '/home/hdc/Android5.1'
============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=5.1
TARGET_PRODUCT=aosp_x86
TARGET_BUILD_VARIANT=eng
TARGET_BUILD_TYPE=release
TARGET_BUILD_APPS=
TARGET_ARCH=x86
TARGET_ARCH_VARIANT=x86
TARGET_CPU_VARIANT=
TARGET_2ND_ARCH=
TARGET_2ND_ARCH_VARIANT=
TARGET_2ND_CPU_VARIANT=
HOST_ARCH=x86_64
HOST_OS=linux
HOST_OS_EXTRA=Linux-5.11.0-40-generic-x86_64-with-Ubuntu-20.04-focal
HOST_BUILD_TYPE=release
BUILD_ID=LMY47D
OUT_DIR=out
============================================
Import includes file: out/target/product/generic_x86/obj/EXECUTABLES/hardweartest_intermediates/import_includes
target  C++: hardweartest <= packages/apps/HardwearTest/hardwaretest.cpp
target Executable: hardweartest (out/target/product/generic_x86/obj/EXECUTABLES/hardweartest_intermediates/LINKED/hardweartest)
target Symbolic: hardweartest (out/target/product/generic_x86/symbols/system/bin/hardweartest)
Export includes file: packages/apps/HardwearTest/Android.mk -- out/target/product/generic_x86/obj/EXECUTABLES/hardweartest_intermediates/export_includes
target Strip: hardweartest (out/target/product/generic_x86/obj/EXECUTABLES/hardweartest_intermediates/hardweartest)
Install: out/target/product/generic_x86/system/bin/hardweartest
make: Leaving directory '/home/hdc/Android5.1'

#### make completed successfully (1 seconds) ####

从输出的Log上看，我们可以知道它在这里：out/target/product/generic_x86/system/bin/hardweartest

编译到system/bin目录下，可是，我们现在的镜像并没有这个程序

所以我们要重新打包镜像

怎么打包叫经？

make snod

执行结果

hdc@ubuntu:~/Android5.1$ make snod
============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=5.1
TARGET_PRODUCT=aosp_x86
TARGET_BUILD_VARIANT=eng
TARGET_BUILD_TYPE=release
TARGET_BUILD_APPS=
TARGET_ARCH=x86
TARGET_ARCH_VARIANT=x86
TARGET_CPU_VARIANT=
TARGET_2ND_ARCH=
TARGET_2ND_ARCH_VARIANT=
TARGET_2ND_CPU_VARIANT=
HOST_ARCH=x86_64
HOST_OS=linux
HOST_OS_EXTRA=Linux-5.11.0-40-generic-x86_64-with-Ubuntu-20.04-focal
HOST_BUILD_TYPE=release
BUILD_ID=LMY47D
OUT_DIR=out
============================================
build/core/Makefile:1013: Warning: with dexpreopt enabled, you may need a full rebuild.
make snod: ignoring dependencies
Target system fs image: out/target/product/generic_x86/system.img
Running:  mkuserimg.sh out/target/product/generic_x86/system out/target/product/generic_x86/system.img ext4 system 786432000 out/target/product/generic_x86/root/file_contexts
make_ext4fs -T -1 -S out/target/product/generic_x86/root/file_contexts -l 786432000 -a system out/target/product/generic_x86/system.img out/target/product/generic_x86/system
Creating filesystem with parameters:
    Size: 786432000
    Block size: 4096
    Blocks per group: 32768
    Inodes per group: 8000
    Inode size: 256
    Journal blocks: 3000
    Label: 
    Blocks: 192000
    Block groups: 6
    Reserved block group size: 47
Created filesystem with 1463/48000 inodes and 130394/192000 blocks
out/target/product/generic_x86/system.img maxsize=802897920 blocksize=2112 total=786432000 reserve=8110080

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

运行结果

运行模拟器

emulator

把模拟器启动起来以后，我们adb shell 进去android系统里

进入到system/bin目录下，查看是否有我们的程序hardweartest

如果有直接执行即可：

图片描述

到次，就和大家了解完了可执行程序的编译和库的编译了