CMake编译目录包含命令include_directories简介

本文使用的相关软件环境信息如下：

软件名称	软件版本
Linux操作系统	Ubuntu 22.04 LTS（X64）
cmake	3.22.1

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

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CMake编译目录包含命令include_directories简介

include_directories

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