macbook:www.funkenstrahlen.de stefan$ gem install RedCloth
Building native extensions.  This could take a while...
ERROR:  Error installing RedCloth:
    ERROR: Failed to build gem native extension.

        /Users/stefan/.rvm/rubies/ruby-1.9.3-p327/bin/ruby extconf.rb
checking for main() in -lc... *** 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=/Users/stefan/.rvm/rubies/ruby-1.9.3-p327/bin/ruby
    --with-redcloth_scan-dir
    --without-redcloth_scan-dir
    --with-redcloth_scan-include
    --without-redcloth_scan-include=${redcloth_scan-dir}/include
    --with-redcloth_scan-lib
    --without-redcloth_scan-lib=${redcloth_scan-dir}/lib
    --with-clib
    --without-clib
/Users/stefan/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:369:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
    from /Users/stefan/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:449:in `try_link0'
    from /Users/stefan/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:464:in `try_link'
    from /Users/stefan/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:607:in `try_func'
    from /Users/stefan/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:833:in `block in have_library'
    from /Users/stefan/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:778:in `block in checking_for'
    from /Users/stefan/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:272:in `block (2 levels) in postpone'
    from /Users/stefan/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:242:in `open'
    from /Users/stefan/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:272:in `block in postpone'
    from /Users/stefan/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:242:in `open'
    from /Users/stefan/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:268:in `postpone'
    from /Users/stefan/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:777:in `checking_for'
    from /Users/stefan/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:828:in `have_library'
    from extconf.rb:5:in `<main>'


Gem files will remain installed in /Users/stefan/.rvm/gems/ruby-1.9.3-p327/gems/RedCloth-4.2.9 for inspection.
Results logged to /Users/stefan/.rvm/gems/ruby-1.9.3-p327/gems/RedCloth-4.2.9/ext/redcloth_scan/gem_make.out