title: ruby-debug won't install / build native extensions
body: <p>I have searched high and low for a solution. I have both <code>linecache19</code> and <code>ruby_core_source</code> installed.</p>
  
  <p>Neither of these commands will work:</p>
  
  <pre><code>gem install ruby-debug19
  gem install ruby-debug19 -- --with-ruby-include=/Users/benjohnson/.rvm/src/ruby-1.9.1-p378
  </code></pre>
  
  <p>Here is the error I keep getting:</p>
  
  <pre><code>Building native extensions.  This could take a while...
  ERROR:  Error installing ruby-debug19:
   ERROR: Failed to build gem native extension.
  
  /Users/benjohnson/.rvm/rubies/ruby-1.9.1-p378/bin/ruby extconf.rb
  checking for rb_method_entry_t.body in method.h... no
  checking for vm_core.h... no
  checking for rb_method_entry_t.body in method.h... no
  checking for vm_core.h... yes
  checking for iseq.h... yes
  checking for insns.inc... yes
  checking for insns_info.inc... yes
  checking for eval_intern.h... yes
  creating Makefile
  
  make
  gcc -I. -I/Users/benjohnson/.rvm/rubies/ruby-1.9.1-p378/include/ruby-1.9.1/i386-darwin10.4.0 -I/Users/benjohnson/.rvm/rubies/ruby-1.9.1-p378/include/ruby-1.9.1/ruby/backward -I/Users/benjohnson/.rvm/rubies/ruby-1.9.1-p378/include/ruby-1.9.1 -I. -DHAVE_VM_CORE_H -DHAVE_ISEQ_H -DHAVE_INSNS_INC -DHAVE_INSNS_INFO_INC -DHAVE_EVAL_INTERN_H -I/Users/benjohnson/.rvm/rubies/ruby-1.9.1-p378/include/ruby-1.9.1/ruby-1.9.1-p378 -fno-common  -O2 -g -Wall -Wno-parentheses  -fno-common -pipe -fno-common  -o breakpoint.o -c breakpoint.c
  gcc -I. -I/Users/benjohnson/.rvm/rubies/ruby-1.9.1-p378/include/ruby-1.9.1/i386-darwin10.4.0 -I/Users/benjohnson/.rvm/rubies/ruby-1.9.1-p378/include/ruby-1.9.1/ruby/backward -I/Users/benjohnson/.rvm/rubies/ruby-1.9.1-p378/include/ruby-1.9.1 -I. -DHAVE_VM_CORE_H -DHAVE_ISEQ_H -DHAVE_INSNS_INC -DHAVE_INSNS_INFO_INC -DHAVE_EVAL_INTERN_H -I/Users/benjohnson/.rvm/rubies/ruby-1.9.1-p378/include/ruby-1.9.1/ruby-1.9.1-p378 -fno-common  -O2 -g -Wall -Wno-parentheses  -fno-common -pipe -fno-common  -o ruby_debug.o -c ruby_debug.c
  ruby_debug.c: In function ‘ruby_method_ptr’:
  ruby_debug.c:141: error: ‘rb_method_entry_t’ undeclared (first use in this function)
  ruby_debug.c:141: error: (Each undeclared identifier is reported only once
  ruby_debug.c:141: error: for each function it appears in.)
  ruby_debug.c:141: error: ‘method’ undeclared (first use in this function)
  ruby_debug.c:142: warning: implicit declaration of function ‘rb_method_entry’
  ruby_debug.c: In function ‘debug_event_hook’:
  ruby_debug.c:719: error: ‘rb_method_entry_t’ undeclared (first use in this function)
  ruby_debug.c:719: error: ‘me’ undeclared (first use in this function)
  make: *** [ruby_debug.o] Error 1
  
  
  Gem files will remain installed in /Users/benjohnson/.rvm/gems/ruby-1.9.1-p378/gems/ruby-debug-base19-0.11.24 for inspection.
  Results logged to /Users/benjohnson/.rvm/gems/ruby-1.9.1-p378/gems/ruby-debug-base19-0.11.24/ext/ruby_debug/gem_make.out
  </code></pre>