CMake, how to include headers without sources?

Question

This is probably a bogus question, but I literally looked at the first two pages of Google without success. I am writing only the header library, and I can’t correctly configure CMake so that when building my solution, this one will be main.cppsuitable. How can I do that?

EDIT

Therefore, I probably should give a slightly more detailed explanation.
Let's say I have a folder ./srcwith: ./src/coreand ./src/wrappers. Inside each folder, I have files .hthat should be included in the file main.cpp:

#include <src/core/reader.h>

Also, when I entered CMakeList.txtsomething like:

include_directories(src/core)
add_executable(main main.cpp)

I get a message like: src/core/reader.hthere is no such file or directory.

Answer 1

, src.
, CMakeLists.txt src, :

include_directories(${CMAKE_SOURCE_DIR})

CMAKE_SOURCE_DIR:

.

src , - :

#include <src/whatever/you/want.h>

---

, :

• :

  include_directories(${CMAKE_SOURCE_DIR}/src)
  

  :

  #include <whatever/you/want.h>
  

  src .

• , , target_include_directories include_directories , :

  target_include_directories(main ${CMAKE_SOURCE_DIR}/src)
  

  add_executable, .

Answer 2

include_directories(), , .

---

.

 #include <src/core/reader.h>

 include_directories(/full_parent_path_of_src)

Answer 3

, CMakeLists.txt include_directories(<DIRECTORY>) .

Answer 4

, , :

add_library(headerlib INTERFACE)
target_include_directories(headerlib INTERFACE ${CMAKE_CURRENT_SOURCE_DIR})

:

target_link_libraries(mytarget headerlib)

, , .