Integrating ROOT into CMake projects

You can integrate ROOT into a CMake based project.
The main interface is the CMake command find_package(…).

Calling find_package(ROOT) makes the following variables available:

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(…) command.
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_CXX_STANDARD	STRING	C++ standard 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`.

One CMake target per ROOT library is also available, e.g. ROOT::Core or ROOT::Tree.

Note

To ensure compatibility between ROOT’s C++ interpreter, Cling, and compiled code, your application must be compiled with the same C++ standard with which ROOT was compiled.
The C++ standard used to build ROOT is available via the ROOT_CXX_STANDARD variable and appears also among the flags listed by root-config --cflags.

Adding additional libraries to `ROOT_LIBRARIES`

You can force additional ROOT libraries in the ROOT_LIBRARIES variable using the COMPONENTS option in the find_package(…) command. For example, to add the RooStats library, you 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)

However, prefer passing libraries as CMake targets whenever possible (see the full example below).

Full example (event project)

The following is an example of a project that creates a library and an executable file.

# CMakeLists.txt for the "event" package. It creates a library and a main program.
# If ROOT is not installed in a default system location you need to tell CMake where to find it.
# Sourcing `thisroot.sh` already sets the required environment variables.
# Otherwise, you must tell the build system where to look for ROOT,
# for example by passing `-DROOT_DIR="/path/to/root/installation` at CMake configuration time.

   cmake_minimum_required(VERSION 3.0 FATAL_ERROR)
   project(event)

# Locate the ROOT package and define a number of useful targets and variables.
   find_package(ROOT REQUIRED COMPONENTS RIO Net)
   include_directories(${CMAKE_CURRENT_SOURCE_DIR}/include)

# Create a shared library.
# Passing cmake targets such as `ROOT::RIO` as dependencies (rather than plain
# library names for example via ${ROOT_LIBRARIES}) ensures that properties such as required
# include directories and C++ standard are propagated to our libraries or executables.
# Note: To ensure compatibility with Cling, targets *must* be compiled using the
# same C++ standard as ROOT was compiled with.
   add_library(Event SHARED Event.cxx)
   target_link_libraries(Event PUBLIC ROOT::RIO ROOT::Net)

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

See also the An Introduction to Modern CMake Guide by Henry Schreiner for more information on building your ROOT project with modern CMake.

Adding additional libraries to ROOT_LIBRARIES

Full example (event project)

Adding additional libraries to `ROOT_LIBRARIES`