Ubuntu12.04 上编译 lua 5.2.3 时，提示需要安装readline5，但是apt 安装时发现 libreadline5-dev 已经不存在了，可选使用 lib64readline5-dev。
则安装使用 sudo apt-get install lib64readline5-dev时遇到问题：
You might want to run 'apt-get -f install' to correct these:
The following packages have unmet dependencies:
lib64readline-gplv2-dev:i386 : Depends: lib64ncurses5-dev:i386 but it is not going to be installed
Depends: libc6-dev-amd64:i386 but it is not going to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).
尝试 apt-get -f install 也无法解决。
然后安装 libc6-dev-amd64也安装不上，提示头文件已被 libc6-dev-i386写入了。
然后卸载 libc6-dev-i386也卸载不了，僵持在哪里。
最后只得强制卸载 lib64nreadline5-dev:
sudo dpkg -r --force-depends lib64readline-gplv2-dev
(Reading database ... 185321 files and directories currently installed.)
Removing lib64readline-gplv2-dev (5.2+dfsg-2) ...
sudo dpkg -r --force-depends lib64ncurses5-dev
(Reading database ... 185316 files and directories currently installed.)
Removing lib64ncurses5-dev (5.9+20140118-1ubuntu1) ...
然后重新安装
apt-get install lib32readline6-dev 解决冲突。
这里就是32位版本库和64位版本库的冲突，显然 ubuntu 还没有合适的处理办法，二者只能选其一。