Gentoo ~ # emerge --update -a libvpx These are the packages that would be merged, in order: Calculating dependencies... done! [ebuild U ] media-libs/libvpx-1.9.0 [1.7.0-r1] !!! Multiple package instances within a single package slot have been pulled !!! into the dependency graph, resulting in a slot conflict: media-libs/libvpx:0 (media-libs/libvpx-1.9.0:0/6::gentoo, ebuild scheduled for merge) USE="highbitdepth postproc svc threads -doc -static-libs -test" ABI_X86="(64) -32 (-x32)" pulled in by media-libs/libvpx (Argument) (media-libs/libvpx-1.7.0-r1:0/5::gentoo, installed) USE="highbitdepth postproc svc threads -doc -static-libs -test" ABI_X86="(64) -32 (-x32)" CPU_FLAGS_X86="avx avx2 mmx sse sse2 sse3 sse4_1 ssse3" pulled in by >=media-libs/libvpx-1.5:0/5=[svc] required by (dev-qt/qtwebengine-5.14.2:5/5.14::gentoo, installed) USE="alsa pulseaudio system-ffmpeg system-icu widgets -bindist -debug -designer -geolocation -jumbo-build -kerberos -test" ABI_X86="(64)" ^^^^^ media-libs/libvpx:0/5= required by (media-video/vlc-3.0.10-r1:0/5-9::gentoo, installed) USE="X a52 alsa chromecast dbus dvbpsi dvd encode ffmpeg flac gcrypt gstreamer jpeg libsamplerate live lua mad matroska mp3 mpeg ncurses ogg png pulseaudio qt5 ssl svg theora upnp vaapi vdpau vorbis vpx x264 x265 zeroconf -aom -archive -aribsub -bidi -bluray -cddb -chromaprint -dav1d -dc1394 -debug (-directx) -dts -faad -fdk -fluidsynth -fontconfig -gme -gnome-keyring -ieee1394 -jack -kate -libass -libcaca -libnotify -libtar -libtiger -linsys -lirc -macosx-notifications -modplug -mtp -musepack -nfs -omxil -optimisememory -opus -projectm -rdp -run-as-root -samba -sdl-image -sftp -shout -sid -skins -soxr -speex -srt -taglib -test -tremor -truetype -twolame -udev -v4l -vnc -wayland -xml -zvbi" ABI_X86="(64)" CPU_FLAGS_X86="mmx sse" ^^^^^ =media-libs/libvpx-1.7*:0/5=[postproc] required by (www-client/firefox-68.11.0:0/0::gentoo, installed) USE="dbus hardened openh264 pulseaudio screenshot system-av1 system-harfbuzz system-icu system-jpeg system-libevent system-libvpx system-sqlite system-webp -bindist -clang -custom-cflags -custom-optimization -debug -eme-free -geckodriver (-gmp-autoupdate) -hwaccel -jack -lto -pgo (-selinux) -startup-notification -test -wayland -wifi" ABI_X86="(64)" CPU_FLAGS_X86="avx2" L10N="-ach -af -an -ar -ast -az -be -bg -bn -br -bs -ca -cak -cs -cy -da -de -dsb -el -en-CA -en-GB -eo -es-AR -es-CL -es-ES -es-MX -et -eu -fa -ff -fi -fr -fy -ga -gd -gl -gn -gu -he -hi -hr -hsb -hu -hy -ia -id -is -it -ja -ka -kab -kk -km -kn -ko -lij -lt -lv -mk -mr -ms -my -nb -nl -nn -oc -pa -pl -pt-BR -pt-PT -rm -ro -ru -si -sk -sl -son -sq -sr -sv -ta -te -th -tr -uk -ur -uz -vi -xh -zh-CN -zh-TW" ^ ^^^^^^^^^ media-libs/libvpx:0/5= required by (media-libs/avidemux-plugins-2.7.4:2.7/2.7::gentoo, installed) USE="aac alsa opengl pulseaudio qt5 vorbis vpx -a52 -aften -amr -dcaenc -debug -dts -fdk -fontconfig -fribidi -jack -lame -libsamplerate -nvenc -opus -oss -truetype -twolame -vdpau -x264 -x265 -xv -xvid" ABI_X86="(64)" CPU_FLAGS_X86="mmx" PYTHON_SINGLE_TARGET="python3_6" ^^^^^ (and 2 more with the same problems) NOTE: Use the '--verbose-conflicts' option to display parents omitted above !!! The slot conflict(s) shown above involve package(s) which may need to !!! be rebuilt in order to solve the conflict(s). However, the following !!! package(s) cannot be rebuilt for the reason(s) shown: (media-libs/avidemux-plugins-2.7.4:2.7/2.7::gentoo, installed): ebuild is masked or unavailable (dev-qt/qtwebengine-5.14.2:5/5.14::gentoo, installed): ebuild is masked or unavailable (media-video/vlc-3.0.10-r1:0/5-9::gentoo, installed): ebuild is masked or unavailable It may be possible to solve this problem by using package.mask to prevent one of those packages from being selected. However, it is also possible that conflicting dependencies exist such that they are impossible to satisfy simultaneously. If such a conflict exists in the dependencies of two different packages, then those packages can not be installed simultaneously. You may want to try a larger value of the --backtrack option, such as --backtrack=30, in order to see if that will solve this conflict automatically. For more information, see MASKED PACKAGES section in the emerge man page or refer to the Gentoo Handbook.