title: How to install ruby-debug when needing necessary libraries and/or headers
body: <p>My Rails is <code>3.2.1.4</code>, Ruby is <code>1.9.3p448</code>.</p>
  
  <p>I got an error when I install <code>ruby-debug</code>:</p>
  
  <pre><code>Building native extensions.  This could take a while...
  ERROR:  Error installing ruby-debug:
          ERROR: Failed to build gem native extension.
  
      /home/hxh/.rvm/rubies/ruby-1.9.3-p448/bin/ruby 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=/home/hxh/.rvm/rubies/ruby-1.9.3-p448/bin/ruby
  
  
  Gem files will remain installed in /home/hxh/.rvm/gems/ruby-1.9.3-p448/gems/linecache-0.46 for inspection.
  Results logged to /home/hxh/.rvm/gems/ruby-1.9.3-p448/gems/linecache-0.46/ext/gem_make.out
  </code></pre>
  
  <p>Who can tell me where the error is?</p>