Gentoo ~ # emerge --ask --changed-use --deep @world
--- Invalid atom in /etc/portage/package.use/vlc: dts
--- Invalid atom in /etc/portage/package.use/vlc: svga

These are the packages that would be merged, in order:

Calculating dependencies... done!

!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:

dev-qt/qtcore:5

  (dev-qt/qtcore-5.13.2-r2:5/5.13::gentoo, installed) USE="icu -debug -systemd -test" ABI_X86="(64)" pulled in by
    ~dev-qt/qtcore-5.13.2 required by (dev-qt/qtxml-5.13.2:5/5.13::gentoo, installed) USE="-debug -test" ABI_X86="(64)"
    ^              ^^^^^^                                                                                                                                       
    (and 1 more with the same problem)

  (dev-qt/qtcore-5.14.1-r1:5/5.14::gentoo, ebuild scheduled for merge) USE="icu -debug -systemd -test" ABI_X86="(64)" pulled in by
    ~dev-qt/qtcore-5.14.1 required by (dev-qt/qtdbus-5.14.1:5/5.14::gentoo, ebuild scheduled for merge) USE="-debug -test" ABI_X86="(64)"
    ^              ^^^^^^                                                                                                                                       
    (and 2 more with the same problem)

dev-libs/nspr:0

  (dev-libs/nspr-4.22:0/0::gentoo, installed) USE="-debug" ABI_X86="(64) -32 (-x32)" pulled in by
    (no parents that aren't satisfied by other packages in this slot)

  (dev-libs/nspr-4.25:0/0::gentoo, ebuild scheduled for merge) USE="-debug" ABI_X86="(64) -32 (-x32)" pulled in by
    >=dev-libs/nspr-4.25[abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?,abi_riscv_lp64d(-)?,abi_riscv_lp64(-)?,abi_s390_32(-)?,abi_s390_64(-)?] required by (dev-libs/nss-3.51:0/0::gentoo, ebuild scheduled for merge) USE="-cacert -utils" ABI_X86="(64) -32 (-x32)"
    ^^              ^^^^                                                                                                                                                                                                                                                                                                        

gnome-base/gsettings-desktop-schemas:0

  (gnome-base/gsettings-desktop-schemas-3.32.0:0/0::gentoo, installed) USE="introspection" ABI_X86="(64)" pulled in by
    (no parents that aren't satisfied by other packages in this slot)

  (gnome-base/gsettings-desktop-schemas-3.34.0:0/0::gentoo, ebuild scheduled for merge) USE="introspection" ABI_X86="(64)" pulled in by
    >=gnome-base/gsettings-desktop-schemas-3.33.0 required by (gnome-base/gvfs-1.42.2:0/0::gentoo, ebuild scheduled for merge) USE="elogind http udev udisks -afp -archive -bluray -cdda -fuse -gnome-keyring -gnome-online-accounts -google -gphoto2 -ios -mtp -nfs -policykit -samba -systemd -test -zeroconf" ABI_X86="(64)"
    ^^                                     ^^^^^^                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

NOTE: Use the '--verbose-conflicts' option to display parents omitted above

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.

For more information, see MASKED PACKAGES section in the emerge man
page or refer to the Gentoo Handbook.


!!! The ebuild selected to satisfy ">=xfce-base/xfce4-session-4.14.0" has unmet requirements.
- xfce-base/xfce4-session-4.14.1::gentoo USE="elogind nls xscreensaver -policykit -systemd" ABI_X86="(64)"

  The following REQUIRED_USE flag constraints are unsatisfied:
    elogind? ( policykit )

  The above constraints are a subset of the following complete expression:
    elogind? ( policykit ) systemd? ( policykit )

(dependency required by "xfce-base/xfce4-meta-4.14-r2::gentoo" [installed])
(dependency required by "@selected" [set])
(dependency required by "@world" [argument])
Gentoo ~ #