如何从另一个include目录中的头文件中访问include目录中的头文件？

Question

I am trying to include multiple directories using target_include_directories in one target, but headers in one include directory cannot access headers in another include directory. How do I solve this problem?

I tried putting the header files into add_library, but it doesn't help. I have also searched here for two hours just now, but I cannot seem to find anything about it.

I am using VC++ by the way.

The following project is simplified, the real project is here .

Project structure:

project
|-- CMakeLists.txt
|-- include
|   |-- project_header.h
|-- subproject
|   |-- CMakeLists.txt
|   |-- include
|   |   |-- subproject_header.h
|   |-- ...
|-- ...

project/CMakeLists.txt :

project("example")
add_subdirectory("subproject")

project/subproject/CMakeLists.txt :

add_executable(example "${PROJECT_SOURCE_DIR}/subproject/source/main.hpp")
set_target_properties(example PUBLIC_HEADER "${PROJECT_SOURCE_DIR}/subproject/include/subproject_header.h" PRIVATE_HEADER "${PROJECT_SOURCE_DIR}/include/project_header.h"
target_include_directories(example PUBLIC "include" PRIVATE "${PROJECT_SOURCE_DIR}/include")

The problem is when I type this into project/subproject/include/subproject_header.h :

...
#include "project_header.h"
...

This will produce an error: fatal error C1083: Cannot open include file: 'project_header.h': No such file or directory

How do I solve this problem?

Edit:

The problem seems to have fixed itself after using .. instead of ${PROJECT_SOURCE_DIR} . Then I change it back to ${PROJECT_SOURCE_DIR} and it still works. Is this related to caching?

Answer 1

Let's say my project is like this:

project
|---include
|   |---common.h
|---library
|---executable

project/CMakeLists.txt :

project(example)
add_subdirectory(library)
add_subdirectory(executable)

project/library/CMakeLists.txt :

add_library(lib ...)
target_include_directories(lib PRIVATE "../include")

project/executable/CMakeLists.txt :

add_executable(exe ...)
target_link_libraries(exe lib)

If I try to access common.h from files in executable , then the compiler will complain about the error mentioned above. This is caused by that PRIVATE include headers will not be included in its dependants.

The solution is to add this to project/projectB/CMakeLists.txt : target_include_directories(exe PRIVATE "../include")