Ruby hangs when trying to install RubyGems

I’ve just set up a minimal Gentoo install and emerged Ruby 1.8.5 from
portage. I then went to emerge rubygems, and found that it hangs.
Manually downloading the file and running ‘ruby setup.rb’ also hangs.
The following are the last few lines I get before nothing happens, and
my CPU sits at 100% (from Ruby):

Successfully built RubyGem
Name: sources
Version: 0.0.1
File: sources-0.0.1.gem

Any help would be great.

A compilation from source makes no difference, either. Is this some
sort of unique Gentoo issue?

I had the same problem both with emerging rubygems or directly running
setup.rb from rubygems-0.9.2.tgz
I fixed it by patching rubygems-0.9.2/lib/rubygems/packages.rb:

< if @io.respond_to? :seek
< # avoid reading…
< - entry.bytes_read, IO::SEEK_CUR)
< else

    #if @io.respond_to? :seek
    #  # avoid reading...
    # - entry.bytes_read, IO::SEEK_CUR)

< end


With that patch you force the TarReader to actually read the file
rather than just seeking into it.
The bug was that by seeking, the bytes_read attribute of entry was
never updated.