Gentoo安裝kdm後啟動kde報錯

在我安裝kdm顯示管理器之前，我的等離子桌面環境執行良好。但是在我安裝kdm並重新啟動我的筆記型電腦後，Gentoo 啟動到帶有白色複選框的黑屏，這就是說

 Could not start kdeinit5, Check your installation.

然後我點擊了okay按鈕。它下降到 tty 並帶有一些錯誤消息。

 xauth: file /root/.serverauth.8002 does not exist

 X.Org X Server 1.18.4
 Release Date: 2016-7-19
 X Protocol Version 11: Revision 0
 Build Operatin System: Linux 4.4.39-gentoo #1 SMP Fri Jan 13 20:24:54 CST 2017 x86_64
 Kernel command line: BOOT_IMAGE=/boot/kernel-genkernel-x86_64-4.4.39-gentoo root=/dev/sda2 rootfstype=ext4 
 Build Date: 13 January 2017 11:03:46PM

 Current version of pixman: 0.34.0
 Before reporting problems., check http://wiki.x.org
 to make sure that you have the latest version.

 (==) Log File: "/var/log/Xorg.0.log", Time: Sat Jan 20 21:12:01 2017 
 (==) Using config directory "/etc/X11/xorg.conf.d"
 (==) Using system config directory "/usr/share/X11/xorg.conf.d"
 The application failed to start because it could not find not find or load the Qt platform plugin "xcd" in ""

 Available platform plugins are: wayland-org.kde.kwin.qpa, minimal, offscreen, wayland, xcb.
 Reinstalling the application may finx this problem.
 startkde: Starting up...
 /usr/bin/kdeinit5: relocation error: /usr/lib64/libQt5Gui.so.5: symbol _Z10qAllocMoreii, version Qt_5 not defined in file libQt5Core.so.5 with link time reference.
 startkde: Could not start kdeinit5. Check your installation.
 xinit: connection to X server lost.
 waiting for X server to shut down (II) Server terminated successfully (0). Closing log file.

但是，在我安裝kdm. 我不知道為什麼我安裝後它崩潰了kdm。

我也從網際網路上找到了一些建議並嘗試了。但這些都不起作用。誰能提供一些解決方案或一些線索？我的環境是：

• 等離子版本是：等離子5.26.0
• kdm 版本是：kde-plasma / kdm-4.11.22
• 核心版本是 4.4.39

首先，感謝@StefanR 為我節省了大量時間！

  正如上面@StefanR 所說，這個問題是由Qt 版本不匹配引起的。在我刪除了kdmbyemerge -C kdm並更新了一些由 引用qt的東西之後emerge -av @qt5-essentials @qt5-addons，我的 kde 桌面環境再次成為一種魅力。

必須提及

  如果您的 portage 聲稱， There are no sets to satisfy 'qt5-essentials'或者There are no sets to satisfy '@qt5-addons'，您的系統中可能缺少某些層，請使用以下命令解決：

 emerge layman
 layman -S
 layman -a qt
 layman -a gentoo 
 emerge --ask @qt5-essentials @qt5-addons

引用自：https://unix.stackexchange.com/questions/341694