必须做两件事。

首先添加要包含的目录:

target_include_directories(test PRIVATE ${YOUR_DIRECTORY})

如果你被一个非常旧的CMake版本(2.8.10或更老)所困，不支持target_include_directories，你也可以使用遗留的include_directories来代替:

include_directories(${YOUR_DIRECTORY})

然后你还必须将头文件添加到当前目标的源文件列表中，例如:

set(SOURCES file.cpp file2.cpp ${YOUR_DIRECTORY}/file1.h ${YOUR_DIRECTORY}/file2.h)
add_executable(test ${SOURCES})

这样，头文件将作为依赖项出现在Makefile中，例如，如果生成了一个Visual Studio项目，头文件也将作为依赖项出现在生成的Visual Studio项目中。

如何使用这些头文件的几个目标:

set(HEADER_FILES ${YOUR_DIRECTORY}/file1.h ${YOUR_DIRECTORY}/file2.h)

add_library(mylib libsrc.cpp ${HEADER_FILES})
target_include_directories(mylib PRIVATE ${YOUR_DIRECTORY})
add_executable(myexec execfile.cpp ${HEADER_FILES})
target_include_directories(myexec PRIVATE ${YOUR_DIRECTORY})

如果与其他创建Makefile的方法(例如make或qmake)相比，CMake更像是一种脚本语言。它不像Python那样酷，但仍然很酷。

如果在各种开源项目中寻找人们如何包含目录，就没有“适当的方法”这样的东西。但是有两种方法。

Crude include_directories will append a directory to the current project and all other descendant projects which you will append via a series of add_subdirectory commands. Sometimes people say that such approach is legacy. A more elegant way is with target_include_directories. It allows to append a directory for a specific project/target without (maybe) unnecessary inheritance or clashing of various include directories. Also allow to perform even a subtle configuration and append one of the following markers for this command.

PRIVATE -仅用于此指定的构建目标

PUBLIC -用于指定目标和与此项目相关的目标

INTERFACE——仅用于与当前项目链接的目标

PS:

这两个命令都允许将目录标记为SYSTEM，以提示指定的目录是否包含警告与您无关。 类似的答案是其他成对的命令target_compile_definitions/add_definitions, target_compile_options/CMAKE_C_FLAGS

首先，使用include_directories()告诉CMake将目录作为-I添加到编译命令行。其次，在add_executable()或add_library()调用中列出头文件。

举个例子，如果你的项目源在src中，你需要include中的头文件，你可以这样做:

include_directories(include)

add_executable(MyExec
  src/main.c
  src/other_source.c
  include/header1.h
  include/header2.h
)

你有两个选择。

旧:

include_directories(${PATH_TO_DIRECTORY})

而新的

target_include_directories(executable-name PRIVATE ${PATH_TO_DIRECTORY})

要使用target_include_directories，您需要定义可执行文件- add_executable(executable-name sourcefiles)。

所以你的代码应该是这样的

add_executable(executable-name sourcefiles)
target_include_directories(executable-name PRIVATE ${PATH_TO_DIRECTORY})

你可以在这里阅读更多内容https://cmake.org/cmake/help/latest/command/target_include_directories.html

项目结构

.
├── CMakeLists.txt
├── external //We simulate that code is provided by an "external" library outside of src
│   ├── CMakeLists.txt
│   ├── conversion.cpp
│   ├── conversion.hpp
│   └── README.md
├── src
│   ├── CMakeLists.txt
│   ├── evolution   //propagates the system in a time step
│   │   ├── CMakeLists.txt
│   │   ├── evolution.cpp
│   │   └── evolution.hpp
│   ├── initial    //produces the initial state
│   │   ├── CMakeLists.txt
│   │   ├── initial.cpp
│   │   └── initial.hpp
│   ├── io   //contains a function to print a row
│   │   ├── CMakeLists.txt
│   │   ├── io.cpp
│   │   └── io.hpp
│   ├── main.cpp      //the main function
│   └── parser   //parses the command-line input
│       ├── CMakeLists.txt
│       ├── parser.cpp
│       └── parser.hpp
└── tests  //contains two unit tests using the Catch2 library
    ├── catch.hpp
    ├── CMakeLists.txt
    └── test.cpp

怎么做

1. 顶层的CMakeLists.txt非常类似于配方1，代码重用函数和宏

cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
  
project(recipe-07 LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_EXTENSIONS OFF)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

include(GNUInstallDirs)
set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY
  ${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_LIBDIR})
set(CMAKE_LIBRARY_OUTPUT_DIRECTORY
  ${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_LIBDIR})
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY
  ${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_BINDIR})

# defines targets and sources
add_subdirectory(src)

# contains an "external" library we will link to
add_subdirectory(external)

# enable testing and define tests
enable_testing()
add_subdirectory(tests)

2.目标和源定义在src/CMakeLists.txt中(转换目标除外)

add_executable(automata main.cpp)
  
add_subdirectory(evolution)
add_subdirectory(initial)
add_subdirectory(io)
add_subdirectory(parser)

target_link_libraries(automata
  PRIVATE
    conversion
    evolution
    initial
    io
    parser
  )

3.转换库定义在external/CMakeLists.txt中

add_library(conversion "")

target_sources(conversion
  PRIVATE
    ${CMAKE_CURRENT_LIST_DIR}/conversion.cpp
  PUBLIC
    ${CMAKE_CURRENT_LIST_DIR}/conversion.hpp
  )

target_include_directories(conversion
  PUBLIC
    ${CMAKE_CURRENT_LIST_DIR}
  )

4.src/CMakeLists.txt文件添加了更多的子目录，这些子目录又包含CMakeLists.txt文件。它们的结构都很相似;src/evolution/CMakeLists.txt包含以下内容:

add_library(evolution "")

target_sources(evolution
  PRIVATE
    ${CMAKE_CURRENT_LIST_DIR}/evolution.cpp
  PUBLIC
    ${CMAKE_CURRENT_LIST_DIR}/evolution.hpp
  )
target_include_directories(evolution
  PUBLIC
    ${CMAKE_CURRENT_LIST_DIR}
  )

5.单元测试注册在tests/CMakeLists.txt中

add_executable(cpp_test test.cpp)

target_link_libraries(cpp_test evolution)

add_test(
  NAME
    test_evolution
  COMMAND
    $<TARGET_FILE:cpp_test>
  )

如何运行它

$ mkdir -p build
$ cd build
$ cmake ..
$ cmake --build .

参考网址:https://github.com/sun1211/cmake_with_add_subdirectory

不要忘记包含${CMAKE_CURRENT_LIST_DIR}。 这就是给我带来麻烦的原因。

示例应该是这样的:

target_include_directories(projectname
    PUBLIC "${CMAKE_CURRENT_LIST_DIR}/include"                          
)

PUBLIC用于您想要包含在父项目中的依赖项。 对于那些你不喜欢的人来说是私密的。