Thanks for the answers @Jayant_Parashar and @glaringlee!
I just do not understand why my compiler ( c++ (Arch Linux 9.3.0-1) 9.3.0) is different from gnu-c++? They do not have exactly the same name, but the arch linux package (https://www.archlinux.org/packages/core/x86_64/gcc/ 13) says it is the gnu compiler. I do not have much experience in this area though, so I am happy if someone can correct me!