There are plenty of symbols which are defined in the library. Notably, much of the language support and all of the standard library exception classes are defined in library.
Even if many of components in the standard C++ library are templates and, thus, have an inline definition, they do benefit from being explicitly instantiated. Using explicitly instantiations of the IOStreams library (and declaring them as
extern templates) greatly improves compile-times.
To figure out what symbols are defined in the library use
nm: it will print the symbols defined and referenced by a library. The names may be mangled which will be fixed by piping the result to a suitable