Can't install thin by using rubygems on Ubuntu 9.10

Question

How can I fix this error, and install thin or other gems?

$ sudo gem install thin
Building native extensions.  This could take a while...
ERROR:  Error installing thin:
    ERROR: Failed to build gem native extension.

/usr/bin/ruby1.9.1 extconf.rb
checking for rb_trap_immediate in ruby.h,rubysig.h... *** 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=/usr/bin/ruby1.9.1
/usr/lib/ruby/1.9.1/mkmf.rb:362:in `try_do': The complier failed to generate an executable file. (RuntimeError)
You have to install development tools first.
    from /usr/lib/ruby/1.9.1/mkmf.rb:425:in `try_compile'
    from /usr/lib/ruby/1.9.1/mkmf.rb:543:in `try_var'
    from /usr/lib/ruby/1.9.1/mkmf.rb:791:in `block in have_var'
    from /usr/lib/ruby/1.9.1/mkmf.rb:668:in `block in checking_for'
    from /usr/lib/ruby/1.9.1/mkmf.rb:274:in `block (2 levels) in postpone'
    from /usr/lib/ruby/1.9.1/mkmf.rb:248:in `open'
    from /usr/lib/ruby/1.9.1/mkmf.rb:274:in `block in postpone'
    from /usr/lib/ruby/1.9.1/mkmf.rb:248:in `open'
    from /usr/lib/ruby/1.9.1/mkmf.rb:270:in `postpone'
    from /usr/lib/ruby/1.9.1/mkmf.rb:667:in `checking_for'
    from /usr/lib/ruby/1.9.1/mkmf.rb:790:in `have_var'
    from extconf.rb:16:in `'


Gem files will remain installed in /var/lib/gems/1.9.1/gems/eventmachine-0.12.10 for inspection.
Results logged to /var/lib/gems/1.9.1/gems/eventmachine-0.12.10/ext/gem_make.out

Addtional Infomation as below

$ cat /etc/issue
Ubuntu 9.10 \n \l
$ dpkg -l | grep ruby
ii  libreadline-ruby1.9.1             1.9.1.243-2                   Readline interface for Ruby 1.9.1
ii  libruby1.9.1                      1.9.1.243-2                   Libraries necessary to run Ruby 1.9.1
ii  ruby1.9.1                         1.9.1.243-2                   Interpreter of object-oriented scripting lan
ii  ruby1.9.1-dev                     1.9.1.243-2                   Header files for compiling extension modules
ii  rubygems1.9.1                     1.3.5-1ubuntu2                package management framework for Ruby librar
$ ruby -v
ruby 1.9.1p243 (2009-07-16 revision 24175) [x86_64-linux]
$ gem list

*** LOCAL GEMS ***

rack (1.1.0)
sinatra (1.0)

Answer 1

i had:

ERROR:  Error installing thin:
    ERROR: Failed to build gem native extension.

/usr/bin/ruby1.8 extconf.rb
checking for rb_trap_immediate in ruby.h,rubysig.h... yes
checking for rb_thread_blocking_region()... no
checking for inotify_init() in sys/inotify.h... yes
checking for writev() in sys/uio.h... yes
checking for rb_thread_check_ints()... no
checking for rb_time_new()... yes
checking for sys/event.h... no
checking for epoll_create() in sys/epoll.h... yes
checking for main() in -lcrypto... no
creating Makefile

make
g++ -I. -I. -I/usr/lib/ruby/1.8/x86_64-linux -I. -DBUILD_FOR_RUBY -DHAVE_RB_TRAP_IMMEDIATE -DHAVE_RBTRAP -DHAVE_INOTIFY_INIT -DHAVE_INOTIFY -DHAVE_WRITEV -DHAVE_WRITEV -DHAVE_RB_TIME_NEW -DOS_UNIX -DHAVE_EPOLL_CREATE -DHAVE_EPOLL -DWITHOUT_SSL -I/include/include    -fPIC -fno-strict-aliasing -g -g -O2  -fPIC    -c emwin.cpp
make: g++: Command not found
make: *** [emwin.o] Error 127

it mentioned that g++ was missing, so i did:

sudo apt-get install g++

and then ran:

sudo gem install thin

and it worked

also, i'm not sure if it may have anything to do with this install, but since it's a 64-bit install, sometimes as precaution, I install the 32 libs:

sudo apt-get install ia32libs

but i always install the 32libs as soon as i setup a new 64-bit server