CMake基础(一) 环境准备与CMake体验

本人使用的系统为 xubuntu_20.04

建立一个C项目

一个原始完整文件

首先创建文件夹 /cmake_tutorials/module1 ,

新建文件 main.cpp

#include <iostream>
using namespace std;

float addition(float num1, float num2)
{
    return num1 + num2;
}
float division(float num1, float num2)
{
    return num1 / num2;
}
void print_result(string result_type, float result_value)
{
    cout << result_type << " result:\t" << result_value << "\n";
}

int main(int argc, char const *argv[])
{
    float first_no, second_no, result_add, result_div;
    cout << "Enter first number\t";
    cin >> first_no;
    cout << "Enter second number\t";
    cin >> second_no;

    result_add = addition(first_no, second_no);
    result_div = division(first_no, second_no);

    print_result("Addition", result_add);
    print_result("Division", result_div);

    // cout << "Addition result:\t" << result_add
    //      << "\n Division result:\t" << result_div << endl;

    return 0;
}

终端执行g++ main.cpp -o calculator，./calculator

Enter first number      90
Enter second number     17
Addition result:        107
Division result:        5.29412

拆分成为多文件

main.cpp

#include <iostream>
using namespace std;

#include "addition.h"
#include "division.h"
#include "print_result.h"

int main(int argc, char const *argv[])
{
    float first_no, second_no, result_add, result_div;
    cout << "Enter first number\t";
    cin >> first_no;
    cout << "Enter second number\t";
    cin >> second_no;

    result_add = addition(first_no, second_no);
    result_div = division(first_no, second_no);

    print_result("Addition", result_add);
    print_result("Division", result_div);

    // cout << "Addition result:\t" << result_add
    //      << "\n Division result:\t" << result_div << endl;

    return 0;
}

addition.h

float addition(float, float);

addition.cpp

float addition(float num1, float num2){return num1 + num2;}

division.h

float division(float, float);

division.cpp

float division(float num1, float num2){return num1 / num2;}

print_result.h

void print_result(string, float);

print_result.cpp

#include <iostream>
using namespace std;

void print_result(string result_type, float result_value)
{cout << result_type << " result:\t" << result_value << "\n";}

构建系统的需求-make

创建makefile

calculator: main.o addition.o division.o print_result.o
		g++ main.o addition.o division.o print_result.o -o calculator

main.o: main.cpp
	g++ -c main.cpp

addition.o: addition.cpp
	g++ -c addition.cpp

division.o: division.cpp
	g++ -c division.cpp

print_result.o: print_result.cpp
	g++ -c print_result.cpp

执行 make，make命令将寻找makefile， 然后构建项目

g++ -c main.cpp
g++ -c addition.cpp
g++ -c division.cpp
g++ -c print_result.cpp
g++ main.o addition.o division.o print_result.o

CMake登场

make:使用生成系统文件生成可执行文件

cmake:用于生成生成系统文件

cmake 通过创建基于平台的系统文件来解决跨平台问题。

安装cmake

方法一： sudo apt install cmake，查看版本cmake --version

方法二：官网下载编译二进制文件 binary distributions

• chmod +x cmake-xxx-linux-xxx.sh 给与运行权限后执行
• 直接进入 xxx/bin文件夹，可以看到 cmake 可执行文件
• 添加 system path ：~/.bashrc文件最下方添加 export PATH=/home/user/xxx/cmake-xxx-linux-xxx/bin:$PATH

方法三：下载源代码 source code

• 解压：tar xvf xxx.tar
• 依次执行以下指令：
• ./bootstrap 如果遇到错误运行：./bootstrap -- -DCMAKE_USE_OPENSSL=OFF
• make
• sudo make install 安装完成

使用CMake生成第一个可执行文件

复制一份文件夹cp -r module1 module2，删除目标文件 rm *.o

构建项目目录：

module2

​ ---my_build_dir

​ ---Other Files

​ ---CMakeLists.txt （CMAKE文件）

编辑CMakeLists.txt，顺序不重要，但可执行文件名必须放在第一位

cmake_minimum_required(VERSION 3.0.0)

project(Calculator_Project VERSION 1.0.0)

add_executable(calculator
main.cpp
addition.cpp
division.cpp
print_result.cpp)

进入my_build_dir，执行 cmake ..生成CMake项目

/module2/my_build_dir$ ls
CMakeCache.txt  CMakeFiles  cmake_install.cmake  Makefile

执行 make

/module2/my_build_dir$ make
Scanning dependencies of target calculator
[ 20%] Building CXX object CMakeFiles/calculator.dir/main.cpp.o
[ 40%] Building CXX object CMakeFiles/calculator.dir/addition.cpp.o
[ 60%] Building CXX object CMakeFiles/calculator.dir/division.cpp.o
[ 80%] Building CXX object CMakeFiles/calculator.dir/print_result.cpp.o
[100%] Linking CXX executable calculator
[100%] Built target calculator

执行ls,可以看到生成的可执行文件calculator

/module2/my_build_dir$ ls
calculator  CMakeCache.txt  CMakeFiles  cmake_install.cmake  Makefile

生成第一个库

编辑CMakeCache.txt

cmake_minimum_required(VERSION 3.0.0)

project(Calculator_Project VERSION 1.0.0)
# 两个库
add_library(my_math
addition.cpp
division.cpp)
add_library(my_print
print_result.cpp)

# target 可执行文件
add_executable(calculator
main.cpp)

# 链接库与可执行文件
target_link_libraries(calculator my_math my_print)

进入my_build_dir，执行cmake .. , make

/module2/my_build_dir$ make
Scanning dependencies of target my_print
[ 14%] Building CXX object CMakeFiles/my_print.dir/print_result.cpp.o
[ 28%] Linking CXX static library libmy_print.a
[ 28%] Built target my_print
Scanning dependencies of target my_math
[ 42%] Building CXX object CMakeFiles/my_math.dir/addition.cpp.o
[ 57%] Building CXX object CMakeFiles/my_math.dir/division.cpp.o
[ 71%] Linking CXX static library libmy_math.a
[ 71%] Built target my_math
Scanning dependencies of target calculator
[ 85%] Linking CXX executable calculator
[100%] Built target calculator

可以看到 库和可执行文件已成功创建

/module2/my_build_dir$ ls
calculator      CMakeFiles           libmy_math.a   Makefile
CMakeCache.txt  cmake_install.cmake  libmy_print.a