Why add header files into ADD_LIBRARY/ADD_EXECUTABLE command in CMake

Question

I had a project which uses CMake as build tool and made a simple template for me and my collegues to use. As I searched for best and easy to use practices online, I've came across different approaches to make a library.

In this template, I've listed header files and source files in two seperate variables, and I'm not passing the headers to add_library command - just sources. And then I use set_target_properties with PUBLIC_HEADER variable to give the header-file list.

So far it seems to work, but I wonder if I'm making thing unnecessarily complex. Some people online give header files to add_library command as well and doesn't even use set_target_properties and such.

In short:

• should we include header files to add_library or should we not (as a best practice)? And impacts of the two usage.
• what is purpose being served by adding headers in the add_library/add_executable? As they seem working even without it (seems forward declaration and symbols only). confirm on understanding please.

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(Here is the template I'm talking about:)

cmake_minimum_required(VERSION 3.1.0)  project(lae CXX C)  set(CMAKE_CXX_STANDARD 14)  include_directories(   ${CMAKE_CURRENT_SOURCE_DIR} )  set(SOURCE_FILES     ... )  set(HEADER_FILES     ... )  set( PRIVATE_HEADER_FILES    ... )  add_library(${PROJECT_NAME} SHARED ${SOURCE_FILES} )   set( REQUIRED_LIBRARIES    ... )  target_link_libraries(${PROJECT_NAME} ${REQUIRED_LIBRARIES} )  SET_TARGET_PROPERTIES(    ${PROJECT_NAME}   PROPERTIES    FRAMEWORK ON   SOVERSION 0   VERSION 0.1.0   PUBLIC_HEADER "${HEADER_FILES}"   PRIVATE_HEADER "${PRIVATE_HEADER_FILES}"   ARCHIVE_OUTPUT_DIRECTORY "lib"   LIBRARY_OUTPUT_DIRECTORY "lib"   OUTPUT_NAME ${PROJECT_NAME} ) 

Answer 1

In our projects we use a "simple" way of yours - add_library with both headers and sources.

If you add only sources, then you won't see headers in IDE-generated project.

However, when installing, we have to do it like that, using two install commands:

install(TARGETS library_name         LIBRARY DESTINATION lib)  install(FILES ${PUBLIC_HEADERS}          DESTINATION include/library_name) 

If you want to do it as a single command, you can use set_target_properties with PUBLIC_HEADER, as you suggested. Then, this kind of install is possible:

install(TARGETS library_name         LIBRARY DESTINATION lib         PUBLIC_HEADER DESTINATION include/library_name) 

Choose the one you like the most and stick to it.