A + or - prefix added to the beginning of a flag in IUSE creates a default USE setting that respectively enables or disables the corresponding USE flag.

Support for the ECONF_SOURCE variable, which is also supported by econf, has been added to the default src_compile implementation. src_compile() { if [[ -x ${ECONF_SOURCE:-.}/configure ]] ; then econf fi if [ -f Makefile ] || [ -f GNUmakefile ] || [ -f makefile ] ; then emake || die "emake failed" fi }

Any valid atom can be constrained to match a specific SLOT. This is accomplished by appending a colon to the atom, followed by a SLOT value. Atom x11-libs/qt:3 ~x11-libs/qt-3.3.8:3 >=x11-libs/qt-3.3.8:3 =x11-libs/qt-3.3*:3