The question is a continuation/repeated one to a previous question, which didn't resolve the issue i'm running into.
Compiling Eigen with make file is one step task. But in Cmake, how do you add a header only library (basically i am using only the Eigen folder from the extracted archive folder in the Eigen website, and disregarding the rest.) Note: Eigen folder has its own CMakeLists.txt
I ran into the same problem today when I wanted to use the stb_image.h library. I solved it this way:
Define the library with the header as input file:
add_library(stb_image SHARED stb_image.h)
As the file does not have a recognized file ending, you have to tell cmake which language the file is in (in this case, C):
set_target_properties(stb_image PROPERTIES LINKER_LANGUAGE C)
Finally, stb_image needs me to define STB_IMAGE_IMPLEMENTATION to enable compilation of the library:
target_compile_definitions(stb_image PRIVATE STB_IMAGE_IMPLEMENTATION)
You can use the FindEigen3.cmake. Put it into cmake/Modules folder and add the following lines to your CmakeLists.txt
set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/Modules/")
find_package(Eigen3 REQUIRED)
include_directories(${EIGEN3_INCLUDE_DIR})
You can find FindEigen3.cmake in the source of the Eigen library in cmake/FindEigen3.cmake
