Directory Structure for Library CMake Projects - c++

Question

I've an Application project Demo which depends on my Shared library Hello. Library Hello should be redistributable. So I need to distribute the headers of Hello as well as use it in my Demo projects. What directory structure and CMake configuration should I use ? I previously had a flat structure and Hello was a header only subdirectory with no CMakeLists.txt. Now I am planning this directory structure.
Demo
main.cpp
app.h
app.cpp
CMakeLists.txt
Hello
includes
matrix.hpp // header only
diagonal.hpp
point.hpp
store.h
analyzer.h
sources
store.cpp
alanyzer.cpp
CMakeLists.txt
Previously the analyzer was header-only which is now splited in header and source. I am mixing header-only things. Is this a good structure ? But I prefer to use the nice #include <Hallo/matrix.hpp> not the ugly one #include "Hallo/includes/matrix.hpp" or just #include "matrix.hpp". I expect this library Hello will be used for other applications and libraries as well.
Demo/CMakeList.txt
CMAKE_MINIMUM_REQUIRED(VERSION 2.6)
PROJECT(Demo)
ADD_SUBDIRECTORY(Demo)
SET(Demo_HEADERS
app.h
)
SET(Demo_SOURCES
app.cpp
main.cpp
)
INCLUDE_DIRECTORIES(${Hello_INCLUDE_DIRS})
# ^^^^ Is this how I need to access the headers ? or just ADD_SUBDIRECTORY() will work
ADD_EXECUTABLE(Demo ${Demo_SOURCES} ${Demo_HEADERS})
TARGET_LINK_LIBRARIES(Demo Hello)
Hello/CMakeLists.txt
CMAKE_MINIMUM_REQUIRED(VERSION 2.6)
PROJECT(Hello)
FIND_PACKAGE(Boost COMPONENTS filesystem program_options thread system serialization date_time chrono REQUIRED)
INCLUDE_DIRECTORIES(${Boost_INCLUDE_DIRS})
SET(Hello_SOURCES
store.cpp
analyzer.cpp
)
INCLUDE_DIRECTORIES((${HELLO_SOURCE_DIR}/includes)
# ^^^^ Is this how I need to access the headers ?
ADD_LIBRARY(Hello ${Hello_SOURCES})
TARGET_LINK_LIBRARIES(Hello ${Boost_LIBRARIES})
I am kind of confused with all this as there is no one specific way to do these all.
--- EDIT ---
Should I have this structure ? or Do some other libraries generally use this structure ? or what are the structures generally practiced ?
hallo
includes
hallo
sources

Answer 1

If you want to access your headers like this:
#include <matrix.hpp>
then you need to include directories. I suggest you the next:
INCLUDE_DIRECTORIES(${Boost_INCLUDE_DIRS})
INCLUDE_DIRECTORIES(${CMAKE_SOURCE_DIR}/Hello/includes)
Your mistake is that you never defines Hello_INCLUDE_DIRS variable in global scope, only in local. So your include do nothing. CMAKE_SOURCE_DIR is always defined and safe to use for includes. Thus you need either define Hello_INCLUDE_DIRS in global scope or use INCLUDE_DIRECTORIES(${CMAKE_SOURCE_DIR}/Hello/includes).
Usage is up to the developer as always. I prefer the structure:
+ Project Root
+-> Build
+-> Documentation
+-> Include
+-> Source
+-> Test
+ CMakeLists.txt
Then I can preset in root CMakeLists.txt next useful variables:
SET(Project_Include_Dir "${CMAKE_SOURCE_DIR}/Include")
SET(Project_Source_Dir "${CMAKE_SOURCE_DIR}/Source")