CMake入门-01-从HelloWorld开始

工作环境

• 系统：macOS Mojave 10.14.6
• CMake: Version 3.15.0-rc4

从 Hello,World! 开始

(1) 新建 hello 目录，创建文件 CMakeLists.txt、main.cpp

$ mkdir hello
$ cd hello
$ touch CMakeLists.txt main.cpp
$ ll
-rw-r--r--  1 staff  staff   124B  8 14 17:19 CMakeLists.txt
-rw-r--r--@ 1 staff  staff   145B  8 14 21:33 main.cpp

(2) 编写程序代码 main.cpp，其代码如下：

#include 

using namespace std;

int main(int argc, char const *argv[]) {
  /* code */
  cout << "Hello,World!" << endl;
  return 0;
}

(3) 编写 CMakeLists.txt，如下：

# cmake 最低版本需求，不加入此行会受到警告信息
cmake_minimum_required(VERSION 3.15.0)

# 项目名设置为 hello
project(hello)

# 将当前目录中的源文件名称赋值给变量 SRC_LIST
aux_source_directory(. SRC_LIST)

# 指示变量 SRC_LIST 中的源文件需要编译成一个名称为 hello 的可执行文件
add_executable(hello ${SRC_LIST})

(4) 执行 cmake & make 编译

# 进入 hello 目录
$ pwd
/Users/staff/Desktop/hello
$ ll
-rw-r--r--@ 1 staff  staff   124B  8 14 17:19 CMakeLists.txt
-rw-r--r--@ 1 staff  staff   145B  8 14 21:33 main.cpp

# 执行 cmake . 命令
$ cmake .
-- The C compiler identification is AppleClang 10.0.1.10010046
-- The CXX compiler identification is AppleClang 10.0.1.10010046
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/staff/Desktop/hello

# 执行 make 命令
$ make
Scanning dependencies of target hello
[ 50%] Building CXX object CMakeFiles/hello.dir/main.cpp.o
[100%] Linking CXX executable hello
[100%] Built target hello

# 运行我们的 hello 程序
$ ./hello
Hello,World!

(5) 外部编译方式

cmake 可以直接在当前目录进行编译，但是，这种做法会将所有生成的中间文件和源代码混在一起，而且 cmake 生成的 makefile 无法跟踪所有的中间文件，即不容易将所有的中间文件删除。

• 之前编译方式的目录（中间文件和源代码混在一起）：

$ pwd
/Users/staff/Desktop/hello

$ ll
-rw-r--r--   1 staff  staff    13K  8 14 21:50 CMakeCache.txt
drwxr-xr-x  12 staff  staff   384B  8 14 21:51 CMakeFiles
-rw-r--r--@  1 staff  staff   124B  8 14 17:19 CMakeLists.txt
-rw-r--r--   1 staff  staff   4.7K  8 14 21:50 Makefile
-rw-r--r--   1 staff  staff   1.3K  8 14 21:50 cmake_install.cmake
-rwxr-xr-x   1 staff  staff    18K  8 14 21:51 hello
-rw-r--r--@  1 staff  staff   145B  8 14 21:33 main.cpp

$ ./hello
Hello,World!

• 使用外部编译方式：

$ pwd
/Users/staff/Desktop/hello
$ ll
-rw-r--r--@ 1 staff  staff   124B  8 14 17:19 CMakeLists.txt
-rw-r--r--@ 1 staff  staff   145B  8 14 21:33 main.cpp

# 在 hello 文件夹中新建 build 文件夹
$ mkdir build
$ cd build
$ pwd
/Users/staff/Desktop/hello/build

# 在 hello/build 文件夹中，执行 cmake & make 编译
$ cmake ..
-- The C compiler identification is AppleClang 10.0.1.10010046
-- The CXX compiler identification is AppleClang 10.0.1.10010046
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/hubin/Desktop/hello/build

$ make
Scanning dependencies of target hello
[ 50%] Building CXX object CMakeFiles/hello.dir/main.cpp.o
[100%] Linking CXX executable hello
[100%] Built target hello

$ ./hello
Hello,World!

• 外部编译方式的目录为：

$ pwd
/Users/staff/Desktop/hello
$ tree .
.
├── CMakeLists.txt
├── build
│   ├── CMakeCache.txt
│   ├── CMakeFiles
│   │   ├── 3.15.0-rc4
│   │   │   ├── ... 省略
│   │   └── progress.marks
│   ├── Makefile
│   ├── cmake_install.cmake
│   └── hello
└── main.cpp

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相关参考：
CMake 官方网站

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