What does this mean?

wdtm.sh

$ which ruby
/Users/david/.rvm/rubies/ruby-1.8.6-p420/bin/ruby
$ gem install ruby-debug
Building native extensions.  This could take a while...
ERROR:  Error installing ruby-debug:
	rbx-require-relative requires Ruby version ~> 1.8.7.

# why is anything rbx related coming into play in an mri 1.8.6 env?????

@dchelimsky: Forgive me my ignorance, but as I am new to Ruby:

to resolve the problem, install linecache-0.45
How to do this? -A simple "gem install linecache" results in the very same error message as beho mentioned (I am also working with v1.9.2p290). tnx

Edit: Seems there is a more underlying problem, at least that's what the "Can't handle 1.9.x yet" below indicates to me (?). So should I delete the whole 1.9.2 stuff and revert to an earlier version?

C:\Ruby192>gem install ruby-debug
ERROR: Error installing ruby-debug:
rbx-require-relative requires Ruby version ~> 1.8.7.

C:\Ruby192>gem list

*** LOCAL GEMS ***

columnize (0.3.4)
minitest (1.6.0)
rake (0.8.7)
rdoc (2.5.8)

C:\Ruby192>gem install linecache -v 0.45
Temporarily enhancing PATH to include DevKit...
Building native extensions. This could take a while...
ERROR: Error installing linecache:
ERROR: Failed to build gem native extension.

    C:/Ruby192/bin/ruby.exe extconf.rb

Can't handle 1.9.x yet
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.

Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=C:/Ruby192/bin/ruby

Gem files will remain installed in C:/Ruby192/lib/ruby/gems/1.9.1/gems/linecache-0.45 for inspection.
Results logged to C:/Ruby192/lib/ruby/gems/1.9.1/gems/linecache-0.45/ext/gem_make.out

C:\Ruby192>

or gem install ruby-debug19