This is typical Ubuntu symlink mayhem.
If you ls -l /usr/bin/c++, you will see it is actually a symbolic link. to:
/etc/alternatives/c++
Which in turn, is also a symbolic link to:
/usr/bin/g++
So, on Ubuntu systems, c++ is g++. The reasoning behind the link indirection is that there are multiple packages that could provide a c++ compiler (such as different versions of g++). You’ll see this a lot on Ubuntu. For example, qmake is a link to a file in /etc/alternatives, which is (on my system) a link back to /usr/bin/qmake-qt3.