CMake include header-only-library into another library, make fail - c++

Question

I have the following folder structure:
- lib/
-libA/
-include/
- libA.h
-src/
- libA.cpp
-CMakeLists.txt (1)
-libB/
-headerB1.h
-headerB2.h
-headerBx.h
-CMakeLists.txt (2)
- src/
-main.cpp
- CMakeLists.txt (3)
in libA.h I try to include one of the header files from libB. In this case that would be headerB1.h by doing
#include <headerB1.h>
But unfortunately, I get the following error in cmake:
fatal error C1083: cannot open include file: 'headerB1.h': No such file or directory from the libA.h file.
I have the following CMake contents:
/CMakeLists.txt (3)
cmake_minimum_required(VERSION 3.10)
project(project)
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED True)
set(SOURCES
src/main.cpp
)
add_executable(${PROJECT_NAME} ${SOURCES})
add_subdirectory("lib/libA")
add_subdirectory("lib/libB")
target_link_libraries(${PROJECT_NAME} PUBLIC libA)
target_link_libraries(${PROJECT_NAME} PUBLIC libB)
lib/libA/CMakeLists.txt (1)
add_library(libA STATIC)
target_sources(libA PRIVATE src/libA.cpp)
target_include_directories(libA
PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include
PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/src
)
lib/libB/CMakeLists.txt (2)
add_library(libB INTERFACE)
target_include_directories(libB INTERFACE ${CMAKE_CURRENT_SOURCE_DIR})
library B (libB) is a header only library in my view (correct me if I'm using the incorrect terms).
So libA actually 'uses' libB but somehow, adding or creating libB is not executed as I thought it would. What are my misconceptions here and how can I solve it?
main.cpp:
#include <libA.h> //This works!
int main(void) {
//do something with libA class / functions
}
libA.h:
#include <headerB1.h> //This causes the cmake (mingw32-make.exe) error
I use:
cmake
vscode
mingw32-make
I actually did take a look at: CMake include library in another library
But making my CMakeLists (1) like the following code did not work for me unfortunately. Or, again, I have misunderstood the solution.
add_library(libA SHARED)
target_sources(libA PRIVATE src/libA.cpp)
target_include_directories(libA
PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include
PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/src
)
target_link_libraries(libA PRIVATE libB)
target_include_directories(libA PUBLIC ${CMAKE_ROOT}/lib/libB)

Answer 1

Ok, this was actually pretty straightforward for a solution but it does make sense that libB would have to be compiled first because libA makes use of it.
So, in CMakeLists.txt (3) I have switched the two following lines:
add_subdirectory("lib/libA")
add_subdirectory("lib/libB")
to
add_subdirectory("lib/libB")
add_subdirectory("lib/libA")
And I also made sure to have added the following code snippet like suggested in the other stackoverflow question, to the libA CMakeLists.txt (1). CMake include library in another library
target_link_libraries(libA PRIVATE libB)
target_include_directories(libA PUBLIC ${CMAKE_ROOT}/lib/libB)
Now, all compiles as expected without errors.