我正在使用 Ubuntu 20.04.1。输出apt-cache policy gcc：
gcc:
Installed: (none)
Candidate: 4:9.2.1-3.1ubuntu1
Version table:
4:9.2.1-3.1ubuntu1 500
500 http://repos.del.extreme-ix.org/ubuntu focal/main amd64 Packages
我之前已经安装了 Codeblocks，现在它显示以下消息：
The following packages have unmet dependencies:
gcc : Depends: cpp (= 4:9.2.1-3.1ubuntu1) but 4:9.3.0-1ubuntu2 is to be installed
Depends: gcc-9 (>= 9.2.1-1~) but it is not going to be installed
Recommends: libc6-dev but it is not going to be installed or
libc-dev
E: Unable to correct problems, you have held broken packages.