Packing libraries for use in and alongside ROOT

[Gordon_Watts]

Hi all,

We are building a small library to be used in the RDF eco-system. We’d like to have it used inside ROOT from the command line, and also be available for linking if someone was building a stand-alone program.

What is the best way to package and distribute this? I’m guessing the recommended advice is to use CMAKE - any hints on using external libraries? Example CMAKE file?

Many thanks in advance!

[eguiraud]

Hi @Gordon_Watts ,
a very basic CMakeLists.txt for a project depending on ROOT looks like this:

cmake_minimum_required(VERSION 3.9)
project (example_root_project CXX)

# Look for ROOT
# As long as an installation is available in the environment, this will succeed.
message(STATUS "Looking for ROOT")
find_package(ROOT REQUIRED COMPONENTS RIO) # can also list components that must be present
message(STATUS "ROOT ${ROOT_VERSION} found at ${ROOT_BINDIR}")

add_subdirectory(src)

with src/CMakeLists.txt that might be similar to what you see here: root_dictionaries_tutorial/CMakeLists.txt at 3fabb4ba134eb8cea49aa119672f301bd1e557cd · eguiraud/root_dictionaries_tutorial · GitHub

Then, to use it in the ROOT prompt you would have to gSystem->Load any library object and #include any header.
To link it when building a standalone program the usual C++ methods work, e.g. adding the installation directory of the project to your LD_LIBRARY_PATH, or cloning the project into the project that depends on it and build them together via cmake.

I can help if you get stuck, although I won’t have time to put together a full blown example before at least next week.
Our build system experts @amadio @oshadura and @bellenot might have more tips and suggestions.

P.S.
@Axel it would be cool to have a cookie-cutter skeleton project that people can clone to jumpstart their project.

[bellenot]

Hi Gordon,

Here is a simple example for an executable (taken from one of my projects):

# Check if cmake has the required version
CMAKE_MINIMUM_REQUIRED(VERSION 3.16 FATAL_ERROR)

set(PROJECT_NAME View3ds)
project(${PROJECT_NAME})

find_package(ROOT REQUIRED)
include(${ROOT_USE_FILE})
if(MSVC)
  set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -SUBSYSTEM:WINDOWS -ENTRY:mainCRTStartup")
endif()
include_directories(${ROOT_INCLUDE_DIRS} ${CMAKE_CURRENT_SOURCE_DIR})
link_directories(${ROOT_LIBRARY_DIR})

# generate dicitonary
ROOT_GENERATE_DICTIONARY(${PROJECT_NAME}Dict ${PROJECT_NAME}.h LINKDEF LinkDef.h)

add_executable(${PROJECT_NAME} ${PROJECT_NAME}.cxx ${PROJECT_NAME}Dict.cxx ${PROJECT_NAME}.rc)
target_link_libraries(${PROJECT_NAME} ${ROOT_LIBRARIES} libEve libGui libGed libRGL)

Cheers, Bertrand.

[Gordon_Watts]

Thanks, to both of you, for this. This is more than enough for us to get started!!

Cheers, Gordon.