geant4-10.4.3-cxx17-removed-features.patch

diff --git a/cmake/Modules/G4BuildSettings.cmake b/cmake/Modules/G4BuildSettings.cmake
index f68cb0a44..6bf4b6948 100644
--- a/cmake/Modules/G4BuildSettings.cmake
+++ b/cmake/Modules/G4BuildSettings.cmake
@@ -205,6 +205,13 @@ endif()
 # Add Definition to flags for temporary back compatibility
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DG4USE_STD11")
 
+# Spack patch to support use of C++ features deprecated/removed in C++17
+# Only checked on AppleClang for now
+if(GEANT4_BUILD_CXXSTD GREATER 14)
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -D_LIBCPP_ENABLE_CXX17_REMOVED_FEATURES=1")
+endif()
+#----
+
 # Hold any appropriate compile flag(s) in variable for later export to
 # config files. Needed to support clients using late CMake 2.8 where compile features
 # are not available.