CMake编译目录包含命令include_directories

本文使用的相关软件环境信息如下：

• include_directories

  命令格式：

  include_directories([AFTER|BEFORE] [SYSTEM] dir1 [dir2 ...])

  该命令主要是将目录添加到编译器的头文件的搜索目录之下，具体介绍见这里。执行该命令后，会将指定的目录添加到当前CMakeLists.txt文件的INCLUDE_DIRECTORIES目录属性和INCLUDE_DIRECTORIES目标文件属性中。接下来看一个实例，看include_directories添加目录之后，INCLUDE_DIRECTORIES属性内容的变化。目录结构如下，后续没有特殊说明，执行命令的目录为include_directories：

  include_directories/
  ├── CMakeLists.txt
  ├── main.cpp
  ├── testdir1
  │   ├── CMakeLists.txt
  │   ├── test1.cpp
  │   └── test1.h
  │   └── testdir1_subdir
  └── testdir2
      ├── CMakeLists.txt
      ├── test2.cpp
      └── test2.hs
  

  include_directories/CMakeLists.txt内容如下：

  cmake_minimum_required(VERSION 3.22)
  project(dir_test)
  
  include_directories(testdir1)
  message("--$ include_directories: testdir1")
  
  
  # 获取当前文件的INCLUDE_DIRECTORIES目录属性
  get_property(dirs DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} PROPERTY INCLUDE_DIRECTORIES)
  message("--$ in directory: ${CMAKE_CURRENT_SOURCE_DIR}, include dir list: ${dirs}")
  
  # 编译testdir1下的库
  add_subdirectory(testdir1)
  message("--$ after compile lib test1")
  get_property(dirs TARGET test1 PROPERTY INCLUDE_DIRECTORIES)
  message("--$ lib test1 include dir list: ${dirs}")
  get_property(dirs DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} PROPERTY INCLUDE_DIRECTORIES)
  message("--$ current file include dir list: ${dirs}")
  
  
  # 编译testdir2下的库
  add_subdirectory(testdir2)
  message("--$ after compile lib test2")
  get_property(dirs TARGET test1 PROPERTY INCLUDE_DIRECTORIES)
  message("--$ lib test1 include dir list: ${dirs}")
  get_property(dirs TARGET test2 PROPERTY INCLUDE_DIRECTORIES)
  message("--$ lib test2 include dir list: ${dirs}")
  get_property(dirs DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} PROPERTY INCLUDE_DIRECTORIES)
  message("--$ current file include dir list: ${dirs}")
  
  
  add_executable(main main.cpp)
  message("--$ after add exe main")
  get_property(dirs TARGET test1 PROPERTY INCLUDE_DIRECTORIES)
  message("--$ lib test1 include dir list: ${dirs}")
  get_property(dirs TARGET test2 PROPERTY INCLUDE_DIRECTORIES)
  message("--$ lib test2 include dir list: ${dirs}")
  get_property(dirs TARGET main PROPERTY INCLUDE_DIRECTORIES)
  message("--$ executable main include dir list: ${dirs}")
  get_property(dirs DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} PROPERTY INCLUDE_DIRECTORIES)
  message("--$ current file include dir list: ${dirs}")
  message("---")
  
  
  target_link_libraries(main test1)
  message("--$ after add lib test1")
  get_property(dirs TARGET test1 PROPERTY INCLUDE_DIRECTORIES)
  message("--$ lib test1 include dir list: ${dirs}")
  get_property(dirs TARGET test2 PROPERTY INCLUDE_DIRECTORIES)
  message("--$ lib test2 include dir list: ${dirs}")
  get_property(dirs TARGET main PROPERTY INCLUDE_DIRECTORIES)
  message("--$ executable main include dir list: ${dirs}")
  get_property(dirs DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} PROPERTY INCLUDE_DIRECTORIES)
  message("--$ current file include dir list: ${dirs}")
  message("---")
  
  
  target_link_libraries(main test2)
  message("--$ after add lib test2")
  get_property(dirs TARGET test1 PROPERTY INCLUDE_DIRECTORIES)
  message("--$ lib test1 include dir list: ${dirs}")
  get_property(dirs TARGET test2 PROPERTY INCLUDE_DIRECTORIES)
  message("--$ lib test2 include dir list: ${dirs}")
  get_property(dirs TARGET main PROPERTY INCLUDE_DIRECTORIES)
  message("--$ executable main include dir list: ${dirs}")
  get_property(dirs DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} PROPERTY INCLUDE_DIRECTORIES)
  message("--$ current file include dir list: ${dirs}")
  message("---")
  
  
  include_directories(testdir2)
  message("--$ include_directories: testdir2")
  get_property(dirs TARGET test1 PROPERTY INCLUDE_DIRECTORIES)
  message("--$ lib test1 include dir list: ${dirs}")
  get_property(dirs TARGET test2 PROPERTY INCLUDE_DIRECTORIES)
  message("--$ lib test2 include dir list: ${dirs}")
  get_property(dirs TARGET main PROPERTY INCLUDE_DIRECTORIES)
  message("--$ executable main include dir list: ${dirs}")
  get_property(dirs DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} PROPERTY INCLUDE_DIRECTORIES)
  message("--$ current file include dir list: ${dirs}")
  message("---")
  

  include_directories/main.cpp内容：

  #include "test1.h"
  #include "test2.h"
  
  int main(int argc, char** argv)
  {
      test1_print();
      test2_print();
  }
  

  include_directories/testdir1/CMakeLists.txt内容如下：

  message("---")
  message("---Enter directory: ${CMAKE_CURRENT_SOURCE_DIR}")
  
  include_directories(testdir1_subdir)
  
  # 获取当前文件的INCLUDE_DIRECTORIES目录属性
  get_property(dirs DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} PROPERTY INCLUDE_DIRECTORIES)
  message("   --$ include dir list: ${dirs}")
  
  add_library(test1 test1.cpp)
  message("   --$ after add lib test1")
  get_property(dirs TARGET test1 PROPERTY INCLUDE_DIRECTORIES)
  message("   --$ lib test1 include dir list: ${dirs}")
  get_property(dirs DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} PROPERTY INCLUDE_DIRECTORIES)
  message("   --$ current file include dir list: ${dirs}")
  
  message("---Exist directory: ${CMAKE_CURRENT_SOURCE_DIR}")
  message("---")
  
  

  include_directories/testdir1/test1.cpp和include_directories/testdir1/test1.h文件内容如下：

  // test1.h
  #ifndef __TEST1_T__
  #define __TEST1_T__
  
  void test1_print();
  
  #endif
  
  // test1.cpp
  #include "test1.h"
  #include <iostream>
  
  void test1_print()
  {
      std::cout << "From test1: hello!" << std::endl;
  }
  
  

  include_directories/testdir2/CMakeLists.txt内容如下：

  message("---")
  message("---Enter directory: ${CMAKE_CURRENT_SOURCE_DIR}")
  
  # 获取当前文件的INCLUDE_DIRECTORIES目录属性
  get_property(dirs DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} PROPERTY INCLUDE_DIRECTORIES)
  message("   --$ include dir list: ${dirs}")
  
  add_library(test2 test2.cpp)
  message("   --$ after add lib test2")
  get_property(dirs TARGET test2 PROPERTY INCLUDE_DIRECTORIES)
  message("   --$ lib test2 include dir list: ${dirs}")
  get_property(dirs DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} PROPERTY INCLUDE_DIRECTORIES)
  message("   --$ current file include dir list: ${dirs}")
  
  message("---Exist directory: ${CMAKE_CURRENT_SOURCE_DIR}")
  message("---")
  

  include_directories/testdir2/test2.cpp和include_directories/testdir2/test2.h文件内容如下：

  // test2.h
  #ifndef __TEST2_T__
  #define __TEST2_T__
  
  void test2_print();
  
  #endif
  
  // test2.cpp
  #include "test2.h"
  #include <iostream>
  
  void test2_print()
  {
      std::cout << "From test2: hello!" << std::endl;
  }
  

  运行cmake .、make以及./main等命令，关键输出如下：

  $cmake .
  ……
  --$ include_directories: testdir1
  --$ in directory: /XXX/include_directories, include dir list: /XXX/include_directories/testdir1
  ---
  ---Enter directory: /XXX/include_directories/testdir1
     --$ include dir list: /XXX/include_directories/testdir1;/XXX/include_directories/testdir1/testdir1_subdir
     --$ after add lib test1
     --$ lib test1 include dir list: /XXX/include_directories/testdir1;/XXX/include_directories/testdir1/testdir1_subdir
     --$ current file include dir list: /XXX/include_directories/testdir1;/XXX/include_directories/testdir1/testdir1_subdir
  ---Exist directory: /XXX/include_directories/testdir1
  ---
  --$ after compile lib test1
  --$ lib test1 include dir list: /XXX/include_directories/testdir1;/XXX/include_directories/testdir1/testdir1_subdir
  --$ current file include dir list: /XXX/include_directories/testdir1
  ---
  ---Enter directory: /XXX/include_directories/testdir2
     --$ include dir list: /XXX/include_directories/testdir1
     --$ after add lib test2
     --$ lib test2 include dir list: /XXX/include_directories/testdir1
     --$ current file include dir list: /XXX/include_directories/testdir1
  ---Exist directory: /XXX/include_directories/testdir2
  ---
  --$ after compile lib test2
  --$ lib test1 include dir list: /XXX/include_directories/testdir1;/XXX/include_directories/testdir1/testdir1_subdir
  --$ lib test2 include dir list: /XXX/include_directories/testdir1
  --$ current file include dir list: /XXX/include_directories/testdir1
  --$ after add exe main
  --$ lib test1 include dir list: /XXX/include_directories/testdir1;/XXX/include_directories/testdir1/testdir1_subdir
  --$ lib test2 include dir list: /XXX/include_directories/testdir1
  --$ executable main include dir list: /XXX/include_directories/testdir1
  --$ current file include dir list: /XXX/include_directories/testdir1
  ---
  --$ after add lib test1
  --$ lib test1 include dir list: /XXX/include_directories/testdir1;/XXX/include_directories/testdir1/testdir1_subdir
  --$ lib test2 include dir list: /XXX/include_directories/testdir1
  --$ executable main include dir list: /XXX/include_directories/testdir1
  --$ current file include dir list: /XXX/include_directories/testdir1
  ---
  --$ after add lib test2
  --$ lib test1 include dir list: /XXX/include_directories/testdir1;/XXX/include_directories/testdir1/testdir1_subdir
  --$ lib test2 include dir list: /XXX/include_directories/testdir1
  --$ executable main include dir list: /XXX/include_directories/testdir1
  --$ current file include dir list: /XXX/include_directories/testdir1
  ---
  --$ include_directories: testdir2
  --$ lib test1 include dir list: /XXX/include_directories/testdir1;/XXX/include_directories/testdir1/testdir1_subdir
  --$ lib test2 include dir list: /XXX/include_directories/testdir1
  --$ executable main include dir list: /XXX/include_directories/testdir1;/XXX/include_directories/testdir2
  --$ current file include dir list: /XXX/include_directories/testdir1;/XXX/include_directories/testdir2
  ---
  -- Configuring done
  -- Generating done
  -- Build files have been written to: /XXX/include_directories
  
  $ make
  Consolidate compiler generated dependencies of target test2
  [ 16%] Building CXX object testdir2/CMakeFiles/test2.dir/test2.cpp.o
  [ 33%] Linking CXX static library libtest2.a
  [ 33%] Built target test2
  Consolidate compiler generated dependencies of target test1
  [ 66%] Built target test1
  Consolidate compiler generated dependencies of target main
  [ 83%] Building CXX object CMakeFiles/main.dir/main.cpp.o
  [100%] Linking CXX executable main
  [100%] Built target main
  
  $ ./main 
  From test1: hello!
  From test2: hello!
  

  以上结果表明了几点：

  1、include_directories添加的目录，会自动添加到当前所在的CMakeLists.txt文件的INCLUDE_DIRECTORIES目录属性，以及在当前CMakeLists.txt文件中定义的目标（通过add_executable/add_library等添加的目标）属性INCLUDE_DIRECTORIES中。

  2、include_directories添加的目录，会传递到当前所在CMakeLists.txt文件中通过add_subdirectory增加的下层CMakeLists.txt中（add_subdirectory语句之后调用的include_directories添加的目录无法传递）。

  3、下层CMakeLists.txt文件中调用的include_directories添加的目录，不会传递到调用它的上层CMakeLists.txt文件。

  4、上层CMakeLists.txt中的include_directories与add_subdirectory相对位置对子CMakeLists.txt中能看到的目录有影响。

  对我们的例子来说：

  1、可执行文件main能看到目录：testdir1、testdir2

  2、库文件test1能看到目录：testdir1、testdir1_subdir，无法看到testdir2，是因为调用add_subdirectory添加子目录testdir1时，还未通过include_directories包含testdir2

  3、库文件test2能看到目录：testdir1，没错！这意味对于本文的例子来说，test2.cpp可以直接包含test1.h文件并调用test1_print()接口