http://gcc.gnu.org/libstdc++/ might be a reference; gcc 3.2 doesn't contain this library (or there is no ebuild for it), which breaks things like kdeaddons.
afaik, libstdc++ is built when you build gcc. If things are breaking because of missing libstdc++ at link time, it more than likely because you updated to a later gcc and haven't re-emerged all things dependent on it.
gcc-3.2 has libstdc++ included all GCCs after gcc-3.0 have it.