Add a check using ROOT_CXX_STANDARD (#540)

* Add a check using ROOT_CXX_STANDARD * Clarify comment * Add a check for matching C++ standard --------- Co-authored-by: jmcarcell <[email protected]>
AIDASoft · Jan 18, 2024 · 139d89b · 139d89b
1 parent 7cb9c42
commit 139d89b
Showing 1 changed file with 18 additions and 3 deletions.
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -85,11 +85,26 @@ else()
   endif()
 endif()
 
-# Check that root is compiled with a modern enough c++ standard
-get_target_property(ROOT_COMPILE_FEATURES ROOT::Core INTERFACE_COMPILE_FEATURES)
-if (NOT "cxx_std_17" IN_LIST ROOT_COMPILE_FEATURES AND NOT "cxx_std_20" IN_LIST ROOT_COMPILE_FEATURES)
+# ROOT_CXX_STANDARD was introduced in https://github.com/root-project/root/pull/6466
+# before that it's an empty variable so we check if it's any number > 0
+if(NOT DEFINED ROOT_CXX_STANDARD)
+  get_target_property(ROOT_COMPILE_FEATURES ROOT::Core INTERFACE_COMPILE_FEATURES)
+  if("cxx_std_17" IN_LIST ROOT_COMPILE_FEATURES)
+    set(ROOT_CXX_STANDARD 17)
+  elseif("cxx_std_20" IN_LIST ROOT_COMPILE_FEATURES)
+    set(ROOT_CXX_STANDARD 20)
+  else()
+    message(FATAL_ERROR "ROOT C++ could not be detected")
+  endif()
+endif()
+
+if(ROOT_CXX_STANDARD VERSION_LESS 17)
   message(FATAL_ERROR "You are trying to build podio against a version of ROOT that has not been built with a sufficient c++ standard. podio requires c++17 or higher")
 endif()
+if(NOT ROOT_CXX_STANDARD VERSION_EQUAL CMAKE_CXX_STANDARD)
+  message(WARNING "You are trying to build podio with a different c++ standard than ROOT. C++${CMAKE_CXX_STANDARD} was required but ROOT was built with C++${ROOT_CXX_STANDARD}")
+endif()
+
 #Check if Python version detected matches the version used to build ROOT
 SET(Python_FIND_FRAMEWORK LAST)
 IF((TARGET ROOT::PyROOT OR TARGET ROOT::ROOTTPython) AND ${ROOT_VERSION} VERSION_GREATER_EQUAL 6.19)