Updates for ROOT

chapters/packages/ROOT.md

@@ -1,8 +1,9 @@
+
 # ROOT
 
 ROOT is a C++ Toolkit for High Energy Physics. It is huge. There are really a lot of ways to use it in CMake, though many/most of the examples you'll find are probably wrong. Here's my recommendation.
 
-Most importantly, there are lots of improvements in CMake in more recent versions of ROOT - try to use 6.14+!
+Most importantly, there are *lots of improvements* in CMake support in more recent versions of ROOT - Using 6.16+ is much, much easier! If you really must support 6.14 or earlier, see the section at the end.
 
 ## Finding ROOT
 
@@ -14,7 +15,7 @@ to attempt to find ROOT. If you don't have your paths set up, you can pass `-DRO
 
 ## The too-simple way
 
-ROOT [provides a utility](https://root.cern.ch/how/integrate-root-my-project-cmake) to set up a ROOT project, which you can activate using `include("${ROOT_USE_FILE}")`. This will automatically make ugly directory level and global variables for you. It will save you a little time setting up, and will waste massive amounts of time later if you try to do anything tricky. As long as you aren't making a library, it's probably fine for simple scripts. Includes and flags are set globally, but you'll still need to link to `${ROOT_LIBRARIES}` yourself, along with possibly `ROOT_EXE_LINKER_FLAGS` (You will have to `separate_arguments` first before linking or you will get an error if there are multiple flags, like on macOS).
+ROOT [provides a utility](https://root.cern.ch/how/integrate-root-my-project-cmake) to set up a ROOT project, which you can activate using `include("${ROOT_USE_FILE}")`. This will automatically make ugly directory level and global variables for you. It will save you a little time setting up, and will waste massive amounts of time later if you try to do anything tricky. As long as you aren't making a library, it's probably fine for simple scripts. Includes and flags are set globally, but you'll still need to link to `${ROOT_LIBRARIES}` yourself, along with possibly `ROOT_EXE_LINKER_FLAGS` (You will have to `separate_arguments` first before linking or you will get an error if there are multiple flags, like on macOS). Also, before 6.16, you have to manually fix a bug in the spacing.
 
 Here's what it would look like:
 
@@ -22,27 +23,17 @@ Here's what it would look like:
 
 ## The right way (Targets)
 
-ROOT 6.12 and earlier do not add the include directory for imported targets. ROOT 6.14+ has corrected this error. To fix this error for older ROOT versions, you'll need something like:
+ROOT 6.12 and earlier do not add the include directory for imported targets. ROOT 6.14+ has corrected this error, and required target properties have been getting better.
-
-[import:'setup_includes', lang:'cmake'](../../examples/root-simple/CMakeLists.txt)
-
-You will also often want the compile flags and definitions:
-
-[import:'setup_flags', lang:'cmake'](../../examples/root-simple/CMakeLists.txt)
-
-In CMake 3.11, you can replace that last function call with:
-
-[import:'modern_fix', lang:'cmake'](../../examples/root-simple-3.11/CMakeLists.txt)
-
-All the ROOT targets will require `ROOT::Core`, so this will be enough regardless of which ROOT targets you need.
 
 To link, just pick the libraries you want to use:
 
 [import:'add_and_link', lang:'cmake'](../../examples/root-simple/CMakeLists.txt)
 
+If you'd like to see the default list, run `root-config --libs` on the command line.
+
 ## Components
 
-Find ROOT allows you to specify components. It will add anything you list to ${ROOT_LIBRARIES}, so you might want to build your own target using that to avoid listing the components twice. This does not solve dependencies though; so it is an error to list `RooFit` but not `RooFitCore`. If you link to `ROOT::RooFit` instead of `${ROOT_LIBRARIES}`, then `RooFitCore` is not required.
+Find ROOT allows you to specify components. It will add anything you list to `${ROOT_LIBRARIES}`, so you might want to build your own target using that to avoid listing the components twice. This did not solve dependencies; it was an error to list `RooFit` but not `RooFitCore`. If you link to `ROOT::RooFit` instead of `${ROOT_LIBRARIES}`, then `RooFitCore` is not required.
 
 ## Dictionary generation
 
@@ -58,7 +49,10 @@ To generate, you should include the following in your CMakeLists:
 
 ```cmake
 include("${ROOT_DIR}/modules/RootNewMacros.cmake")
-include_directories(ROOT_BUG)
+
+# Uncomment for ROOT versions than 6.16
+# They break if nothing is in the global include list!
+# include_directories(ROOT_BUG)
 ```
 
 The second line is due to a bug in the NewMacros file that causes dictionary generation to fail if there is not at least one global include directory or a `inc` folder. Here I'm including a non-existent directory just to make it work. There is no `ROOT_BUG` directory.
@@ -79,3 +73,42 @@ The final two output files must sit next to the library output. This is done by
 
 [linkdef-root]: https://root.cern.ch/selecting-dictionary-entries-linkdefh
 
+---
+
+# Using Old ROOT
+
+If you really have to use older ROOT, you'll need something like this:
+
+```cmake
+# ROOT targets are missing includes and flags in ROOT 6.10 and 6.12
+set_property(TARGET ROOT::Core PROPERTY
+    INTERFACE_INCLUDE_DIRECTORIES "${ROOT_INCLUDE_DIRS}")
+
+# Early ROOT does not include the flags required on targets
+add_library(ROOT::Flags_CXX IMPORTED INTERFACE)
+
+
+# ROOT 6.14 and earlier have a spacing bug in the linker flags
+string(REPLACE "-L " "-L" ROOT_EXE_LINKER_FLAGS "${ROOT_EXE_LINKER_FLAGS}")
+
+# Fix for ROOT_CXX_FLAGS not actually being a CMake list
+separate_arguments(ROOT_CXX_FLAGS)
+set_property(TARGET ROOT::Flags_CXX APPEND PROPERTY
+    INTERFACE_COMPILE_OPTIONS ${ROOT_CXX_FLAGS})
+
+# Add definitions
+separate_arguments(ROOT_DEFINITIONS)
+foreach(_flag ${ROOT_EXE_LINKER_FLAG_LIST})
+    # Remove -D or /D if present
+    string(REGEX REPLACE [=[^[-//]D]=] "" _flag ${_flag})
+    set_property(TARGET ROOT::Flags APPEND PROPERTY INTERFACE_LINK_LIBRARIES ${_flag})
+endforeach()
+
+# This also fixes a bug in the linker flags
+separate_arguments(ROOT_EXE_LINKER_FLAGS)
+set_property(TARGET ROOT::Flags_CXX APPEND PROPERTY
+    INTERFACE_LINK_LIBRARIES ${ROOT_EXE_LINKER_FLAGS})
+
+# Make sure you link with ROOT::Flags_CXX too!
+```
+

examples/CMakeLists.txt

@@ -10,5 +10,4 @@ add_subdirectory(extended-project)
 
 add_subdirectory(root-usefile)
 add_subdirectory(root-simple)
-add_subdirectory(root-simple-3.11)
 add_subdirectory(root-dict)

examples/root-dict/CMakeLists.txt

@@ -1,6 +1,6 @@
 
 ## [main]
-cmake_minimum_required(VERSION 3.4)
+cmake_minimum_required(VERSION 3.4...3.15)
 
 project(RootDictExample LANGUAGES CXX)
 
@@ -9,21 +9,14 @@ set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 set(CMAKE_PLATFORM_INDEPENDENT_CODE ON)
 
-find_package(Threads)
-
 find_package(ROOT CONFIG REQUIRED)
 include("${ROOT_DIR}/modules/RootNewMacros.cmake")
 
-# We will set the flags ourselves
-set_target_properties(ROOT::Core PROPERTIES
-    INTERFACE_INCLUDE_DIRECTORIES "${ROOT_INCLUDE_DIRS}")
-
-include_directories(ROOT_BUG)
 root_generate_dictionary(G__DictExample DictExample.h LINKDEF DictLinkDef.h)
 
 add_library(DictExample SHARED DictExample.cxx DictExample.h G__DictExample.cxx)
 target_include_directories(DictExample PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}")
-target_link_libraries(DictExample PUBLIC ROOT::Core Threads::Threads)
+target_link_libraries(DictExample PUBLIC ROOT::Core)
 
 ## [main]
 

examples/root-simple-3.11/CMakeLists.txt

@@ -1,34 +0,0 @@
-
-## [main]
-cmake_minimum_required(VERSION 3.11)
-
-project(RootSimpleExample311 LANGUAGES CXX)
-
-find_package(ROOT CONFIG REQUIRED)
-
-## [modern_fix]
-target_include_directories(ROOT::Core INTERFACE "${ROOT_INCLUDE_DIRS}")
-
-add_library(ROOT::Flags_CXX IMPORTED INTERFACE)
-
-separate_arguments(ROOT_CXX_FLAGS)
-target_compile_options(ROOT::Flags_CXX INTERFACE ${ROOT_CXX_FLAGS})
-
-separate_arguments(ROOT_DEFINITIONS)
-target_compile_definitions(ROOT::Flags_CXX INTERFACE ${ROOT_DEFINITIONS})
-
-# This fixes a bug in the linker flags
-string(REPLACE "-L " "-L" ROOT_EXE_LINKER_FLAGS "${ROOT_EXE_LINKER_FLAGS}")
-separate_arguments(ROOT_EXE_LINKER_FLAGS)
-# Stuck into using old property method due to separate -L and -l arguments
-# (A full path to -l is better!)
-set_property(TARGET ROOT::Flags_CXX PROPERTY
-    INTERFACE_LINK_LIBRARIES ${ROOT_EXE_LINKER_FLAGS})
-## [modern_fix]
-
-add_executable(RootSimpleExample311 SimpleExample.cxx)
-target_link_libraries(RootSimpleExample311 PUBLIC ROOT::Physics ROOT::Flags_CXX)
-## [main]
-
-enable_testing()
-add_test(NAME RootSimpleExample311 COMMAND RootSimpleExample311)

examples/root-simple-3.11/README.md

@@ -1,11 +0,0 @@
-# A Simple ROOT Project (CMake 3.11)
-
-This is a minimal example of a ROOT project using the target system and without a dictionary.
-This uses the new support in CMake 3.11+ for adding interface properties on an imported interface target.
-
-#### examples/root-simple-3.11/CMakeLists.txt
-[import:'main', lang:'cmake'](CMakeLists.txt)
-
-#### examples/root-simple-3.11/SimpleExample.cxx
-
-[import](SimpleExample.cxx)

examples/root-simple-3.11/SimpleExample.cxx

@@ -1,7 +0,0 @@
-#include <TLorentzVector.h>
-
-int main() {
-    TLorentzVector v(1,2,3,4);
-    v.Print();
-    return 0;
-}

examples/root-simple/CMakeLists.txt

@@ -1,46 +1,19 @@
 
 ## [main]
-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.1...3.15)
 
 project(RootSimpleExample LANGUAGES CXX)
 
+# Finding the ROOT package
 ## [find_package]
-find_package(ROOT CONFIG REQUIRED)
+find_package(ROOT 6.16 CONFIG REQUIRED)
 ## [find_package]
 
-# ROOT targets are missing includes and flags
-## [setup_includes]
-set_property(TARGET ROOT::Core PROPERTY
-    INTERFACE_INCLUDE_DIRECTORIES "${ROOT_INCLUDE_DIRS}")
-## [setup_includes]
 
-## [setup_flags]
+# Adding an executable program and linking to needed ROOT libraries
-add_library(ROOT::Flags_CXX IMPORTED INTERFACE)
-
-# Fix for ROOT_CXX_FLAGS not actually being a CMake list
-separate_arguments(ROOT_CXX_FLAGS)
-set_property(TARGET ROOT::Flags_CXX APPEND PROPERTY
-    INTERFACE_COMPILE_OPTIONS ${ROOT_CXX_FLAGS})
-
-# Add definitions
-separate_arguments(ROOT_DEFINITIONS)
-foreach(_flag ${ROOT_EXE_LINKER_FLAG_LIST})
-    # Remove -D or /D if present
-    string(REGEX REPLACE [=[^[-//]D]=] "" _flag ${_flag})
-    set_property(TARGET ROOT::Flags APPEND PROPERTY INTERFACE_LINK_LIBRARIES ${_flag})
-endforeach()
-
-# This also fixes a bug in the linker flags
-string(REPLACE "-L " "-L" ROOT_EXE_LINKER_FLAGS "${ROOT_EXE_LINKER_FLAGS}")
-separate_arguments(ROOT_EXE_LINKER_FLAGS)
-set_property(TARGET ROOT::Flags_CXX APPEND PROPERTY
-    INTERFACE_LINK_LIBRARIES ${ROOT_EXE_LINKER_FLAGS})
-## [setup_flags]
-
-# Adding an exectuable program and linking to needed ROOT libraries
 ## [add_and_link]
 add_executable(RootSimpleExample SimpleExample.cxx)
-target_link_libraries(RootSimpleExample PUBLIC ROOT::Physics ROOT::Flags_CXX)
+target_link_libraries(RootSimpleExample PUBLIC ROOT::Physics)
 ## [add_and_link]
 
 ## [main]

examples/root-usefile/CMakeLists.txt

@@ -1,16 +1,18 @@
 
 ## [main]
-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.1...3.15)
 
 project(RootUseFileExample LANGUAGES CXX)
 
-find_package(ROOT CONFIG REQUIRED)
+find_package(ROOT 6.16 CONFIG REQUIRED)
 
+# Sets up global settings
 include("${ROOT_USE_FILE}")
 
+# This is required for ROOT < 6.16
+# string(REPLACE "-L " "-L" ROOT_EXE_LINKER_FLAGS "${ROOT_EXE_LINKER_FLAGS}")
+
 # This is required on if there is more than one flag (like on macOS)
-# and this also fixes a bug in the linker flags
-string(REPLACE "-L " "-L" ROOT_EXE_LINKER_FLAGS "${ROOT_EXE_LINKER_FLAGS}")
 separate_arguments(ROOT_EXE_LINKER_FLAGS)
 
 add_executable(RootUseFileExample SimpleExample.cxx)