Ok, so I tried a rebuild which for some reason didn’t use C++17 but C++14 bbased of root-config output.
So just to be clear, my build command, following : Building ROOT from source - ROOT
Should actually be:
cmake -DCMAKE_CXX_STANDARD=17 -DCMAKE_INSTALL_PREFIX=../root_install/ ../root_src/ correct? I see other posts mentioning -Dcxx17=ON (Enable C++14/17 support after building ROOT) would this also be needed?