installsources feature of Portage is useful to have source code available for installed packages for debugging purposes. The feature will cause Portage to copy the source code used to build a package to an appropriate subdirectory of
/usr/src/debug. For example, if
=x11-libs/gtksourceview-2.10.5-r1 is installed, then its source code would be found in
/usr/src/debug/x11-libs/gtksourceview-2.10.5-r1. In order to use this feature,
debugedit needs to be installed.
To enable installsources add the following to the bottom of /etc/make.conf.