How to Integrate ROOT into my project with CMake

Integrating ROOT into your CMake based project should be straight forward. The main interface is the CMake command find_package(…), which defines the following standard variables:

variable type description
ROOT_INCLUDE_DIRS PATH include directories for the ROOT installation
ROOT_LIBRARIES LIST Libraries to link against. The actual list of libraries is composed using the COMPONENTS listed in the find_package(…)
ROOT_DEFINITIONS STRING Compile definitions needed to use ROOT
ROOT_CXX_FLAGS STRING C++ compiler flags used to build ROOT
ROOT_CC_FLAGS STRING C compiler flags used to build ROOT
ROOT_<library>_LIBRARY PATH Full path for each of the ROOT libraries listed in COMPONENTS
ROOT_<command>_CMD PATH Full path for each ROOT executable (rootcling, root, hadd, etc.)
ROOT_<option>_FOUND BOOL True for each enabled build option (e.g. cocoa, python, xrootd, etc.)
ROOT_FOUND BOOL True if the ROOT package has been found
ROOT_USE_FILE PATH Path to a CMake module which makes use of the previous variables and loads modules with useful macros or functions such as ROOT_GENERATE_DICTIONARY

Adding Additional libraries

The user can force additional ROOT libraries in the ROOT_LIBRARIES variable using the COMPONENTS option in find_package(...) command. For example to add the RooStats library the user can specify it as an extra component (the name of the component is the name of the library without any library prefix or suffix).

find_package(ROOT COMPONENTS RooStats)

Useful commands

ROOT provides a number of CMake macros/functions that are used internally but can also be used by projects layered on top of ROOT.


Generate dictionary for a set of header files (convenient wrapper on top of rootcling command).

ROOT_GENERATE_DICTIONARY( dictionary headerfiles ... [STAGE1] 
                         LINKDEF linkdeffiles ...
                         [MODULE module] [DEPENDENCIES dep1 dep2 ...]
                         [OPTIONS opt1 opt2 ...] )

The file {dictionary}.cxx and {dictionary}.pcm are created using the header and linkdef files calling the rootcling command. Optionally OPTIONS and MODULE can be provided to customize the way the rootcling is called and the name for the .pcm files.


Generate dictionary for a set of header files (convenient wrapper on top of rootcling command).

REFLEX_GENERATE_DICTIONARY( dictionary headerfiles ...
                          SELECTION selection ...
                          [DEPENDENCIES dep1 dep2 ...]
                          [OPTIONS opt1 opt2 ...] )

The file {dictionary}.cxx and {dictionary}.pcm are created using the headers and selection file calling the genreflex command. Optionally OPTIONS can be provided to customize the way the genreflex is called.

Full example (Event project)

Following is an example of a project that creates a library including a dictionary and an executable.

# CMakeLists.txt for event package. It creates a library with dictionary and a main program
cmake_minimum_required(VERSION 3.0 FATAL_ERROR)

# You need to tell CMake where to find the ROOT installation. This can be done in a number of ways:
#   - ROOT built with classic configure/make use the provided $ROOTSYS/etc/cmake/FindROOT.cmake
#   - ROOT built with CMake. Add in CMAKE_PREFIX_PATH the installation prefix for ROOT

#---Locate the ROOT package and defines a number of variables (e.g. ROOT_INCLUDE_DIRS)

#---Define useful ROOT functions and macros (e.g. ROOT_GENERATE_DICTIONARY)


#---Create a shared library with geneated dictionary
add_library(Event SHARED Event.cxx G__Event.cxx)
target_link_libraries(Event ${ROOT_LIBRARIES})

#---Create  a main program using the library
add_executable(Main MainEvent.cxx)
target_link_libraries(Main Event)