...

Eclipse can be used as a C/C++ development environment. You need to install the C/C++ Development Toolkit (CDT) that can be found at http://www.eclipse.org/cdt/ .
You will need to get Eclipse (version 3.3.0 at least) (http://www.eclipse.org/downloads/) and the Eclipse CDT (download.eclipse.org/tools/cdt/releases/europa).

Please see this document for more details.

Eclipse on Gentoo

...