Note: Portage cleans up almost everything after a package has been successfully merged unless FEATURES contains 'noclean'. Adding noclean to FEATURES will cause a lot of files to remain and will consume large amounts of space, very quickly. It is not recommended to leave this on, unless you have use for the sources post-merge. Optionally, one may manually clean these files with rm -rf /var/tmp/portage.
If you're creating an ebuild, you'll want to make sure that the S (source directory) variable defined at the top of your ebuild script points to the directory that contains your extracted sources. This directory is defined by default to be ${WORKDIR}/${P}, so it is not often required. The src_unpack() function is also responsible for making the appropriate patches to the sources so that they're ready for compilation.
Achim Gottinger <achim@gentoo.org> Daniel Robbins <drobbins@gentoo.org> Nicholas Jones <carpaski@gentoo.org> Mike Frysinger <vapier@gentoo.org>