# emerge -av1 --deep --update --backtrack=500 qtcore
These are the packages that would be merged, in order:

Calculating dependencies... done!
Dependency resolution took 51.00 s.

[ebuild     U  ] sys-apps/systemd-utils-254.5-r2::gentoo [252.7::gentoo] USE="acl kmod (split-usr) tmpfiles udev* -boot -kernel-install% -secureboot% (-selinux) -sysusers -test -ukify%" ABI_X86="32* (64) (-x32)" PYTHON_SINGLE_TARGET="python3_11%* -python3_10% (-python3_12)" 0 KiB
[uninstall     ] sys-fs/eudev-3.2.11-r2::gentoo  USE="introspection kmod -rule-generator (-selinux) -static-libs -test" ABI_X86="32 (64) (-x32)" 
[blocks b      ] sys-apps/systemd-utils[udev] ("sys-apps/systemd-utils[udev]" is soft blocking sys-fs/eudev-3.2.11-r2)
[blocks b      ] sys-fs/eudev ("sys-fs/eudev" is soft blocking sys-apps/systemd-utils-254.5-r2)
[ebuild     U  ] virtual/libudev-251-r2:0/1::gentoo [232-r7:0/1::gentoo] USE="-systemd" ABI_X86="32 (64) (-x32)" 0 KiB
[ebuild     U  ] virtual/udev-217-r7::gentoo [217-r5::gentoo] USE="-systemd%" 0 KiB
[ebuild     U  ] sys-apps/util-linux-2.38.1-r2::gentoo [2.38.1::gentoo] USE="cramfs hardlink logger ncurses nls pam python readline (split-usr) su suid udev (unicode) -audit -build -caps -cryptsetup -fdformat -kill -magic (-rtas) (-selinux) -slang -static-libs -systemd -test -tty-helpers -verify-sig" ABI_X86="32 (64) (-x32)" PYTHON_TARGETS="python3_11* -python3_10* (-python3_9%)" 0 KiB
[ebuild     U  ] dev-libs/libinput-1.24.0:0/10::gentoo [1.22.1:0/10::gentoo] USE="-doc -test" INPUT_DEVICES="-wacom" 0 KiB
[ebuild     U  ] sys-auth/elogind-246.10-r3::gentoo [246.10-r2::gentoo] USE="acl cgroup-hybrid pam policykit -audit -debug -doc (-selinux) -test" 0 KiB
[ebuild  r  U  ] dev-qt/qtgui-5.15.11-r2:5/5.15.11::gentoo [5.15.8-r3:5/5.15.8::gentoo] USE="X accessibility* dbus egl jpeg libinput png udev vulkan* -debug -eglfs -evdev -gles2-only -ibus -linuxfb -test -tslib -tuio -vnc -wayland" 0 KiB
[ebuild     U  ] sys-apps/portage-3.0.51::gentoo [3.0.44-r1::gentoo] USE="(ipc) native-extensions rsync-verify xattr -apidoc -build -doc -gentoo-dev (-selinux) -test" PYTHON_TARGETS="python3_11* (-pypy3) -python3_10* (-python3_12) (-python3_9%)" 0 KiB
[ebuild     U  ] dev-qt/qtx11extras-5.15.11:5/5.15::gentoo [5.15.8:5/5.15::gentoo] USE="-debug -test" 0 KiB
[ebuild     U  ] app-crypt/pinentry-1.2.1-r3::gentoo [1.2.1-r1::gentoo] USE="X%* gtk ncurses qt5 -caps -efl -emacs -keyring% -verify-sig -wayland% (-gnome-keyring%*)" 0 KiB

Total: 10 packages (10 upgrades, 1 uninstall), Size of downloads: 0 KiB
Conflict: 2 blocks (all satisfied)

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

dev-qt/qtgui:5

  (dev-qt/qtgui-5.15.11-r2:5/5.15.11::gentoo, ebuild scheduled for merge) USE="X accessibility dbus egl jpeg libinput png udev vulkan -debug -eglfs -evdev -gles2-only -ibus -linuxfb -test -tslib -tuio -vnc -wayland" ABI_X86="(64)" pulled in by
    =dev-qt/qtgui-5.15.11*[X] required by (dev-qt/qtx11extras-5.15.11:5/5.15::gentoo, ebuild scheduled for merge) USE="-debug -test" ABI_X86="(64)"
    ^             ^^^^^^^^                                                                                                                                                                                                                                         

  (dev-qt/qtgui-5.15.8-r3:5/5.15.8::gentoo, installed) USE="X dbus egl jpeg libinput png udev userland_GNU -accessibility -debug -eglfs -evdev -gles2-only -ibus -linuxfb -test -tslib -tuio -vnc -vulkan -wayland" ABI_X86="(64)" pulled in by
    =dev-qt/qtgui-5.15.8* required by (dev-qt/qtquickcontrols2-5.15.8:5/5.15::gentoo, installed) USE="userland_GNU widgets -debug -test" ABI_X86="(64)"
    ^             ^^^^^^^                                                                                                                                                                                                                                                                                    
    (and 10 more with the same problem)

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.