Joel, thanks for information.

I ran into this problem, but the patch command didn't work, seemed to 
loop, even after deleting the last hunk.

I had to edit manually the readline.c and extconf.rb file like the patch 
should have do it and then I was able to build ruby 2.1.1.

Regards,
Michel.

>
> If you're running into the readline compile problem on ubuntu 14.04, 
> this is one fix:
>
> https://gist.github.com/mislav/a18b9d7f0dc5b9efc162
>
> Download the readline.patch file from this gist (click on "raw" and 
> download that link).
>
> Go into your ruby-2.1.1 dir. Type this:
>
> patch -p0 <path/to/the/readline.patch
>
> I had to delete the last hunk from the patch file for it to work. (The 
> last hunk is only comments.)
>