CMake入門-01-從HelloWorld開始

工做環境

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

從 Hello,World! 開始

(1) 新建 hello 目錄，建立文件 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) 編寫程序代碼 main.cpp，其代碼以下：

#include <iostream>

using namespace std;

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

(3) 編寫 CMakeLists.txt，以下：

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

# 項目名設置爲 hello
project(hello)

# 將當前目錄中的源文件名稱賦值給變量 SRC_LIST
aux_source_directory(. SRC_LIST)

# 指示變量 SRC_LIST 中的源文件須要編譯成一個名稱爲 hello 的可執行文件
add_executable(hello ${SRC_LIST})

(4) 執行 cmake & make 編譯

# 進入 hello 目錄
$ 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

# 執行 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

# 執行 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

# 運行咱們的 hello 程序
$ ./hello
Hello,World!

(5) 外部編譯方式

cmake 能夠直接在當前目錄進行編譯，可是，這種作法會將全部生成的中間文件和源代碼混在一塊兒，並且 cmake 生成的 makefile 沒法跟蹤全部的中間文件，即不容易將全部的中間文件刪除。

• 以前編譯方式的目錄（中間文件和源代碼混在一塊兒）：

$ 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!

• 使用外部編譯方式：

$ 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 文件夾中新建 build 文件夾
$ mkdir build
$ cd build
$ pwd
/Users/staff/Desktop/hello/build

# 在 hello/build 文件夾中，執行 cmake & make 編譯
$ 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!

• 外部編譯方式的目錄爲：

$ 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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