sudo gem install ruby-debug19

yard (master)$ sudo gem install ruby-debug19
Password:
Building native extensions.  This could take a while...
Building native extensions.  This could take a while...
ERROR:  Error installing ruby-debug19:
	ERROR: Failed to build gem native extension.

/usr/local/bin/ruby19 extconf.rb
checking for vm_core.h... no
checking for vm_core.h... yes
checking for iseq.h... yes
checking for insns.inc... yes
checking for insns_info.inc... yes
creating Makefile

make
gcc -I. -I/usr/local/include/ruby19-1.9.1/i386-darwin9.6.0 -I/usr/local/include/ruby19-1.9.1/ruby/backward -I/usr/local/include/ruby19-1.9.1 -I. -DHAVE_VM_CORE_H -DHAVE_ISEQ_H -DHAVE_INSNS_INC -DHAVE_INSNS_INFO_INC -I/usr/local/include/ruby19-1.9.1/ruby-1.9.1-p0 -fno-common  -O2 -g -Wall -Wno-parentheses -pipe -fno-common  -o breakpoint.o -c breakpoint.c
gcc -I. -I/usr/local/include/ruby19-1.9.1/i386-darwin9.6.0 -I/usr/local/include/ruby19-1.9.1/ruby/backward -I/usr/local/include/ruby19-1.9.1 -I. -DHAVE_VM_CORE_H -DHAVE_ISEQ_H -DHAVE_INSNS_INC -DHAVE_INSNS_INFO_INC -I/usr/local/include/ruby19-1.9.1/ruby-1.9.1-p0 -fno-common  -O2 -g -Wall -Wno-parentheses -pipe -fno-common  -o ruby_debug.o -c ruby_debug.c
ruby_debug.c: In function ‘ruby_method_ptr’:
ruby_debug.c:142: error: ‘rb_method_entry_t’ undeclared (first use in this function)
ruby_debug.c:142: error: (Each undeclared identifier is reported only once
ruby_debug.c:142: error: for each function it appears in.)
ruby_debug.c:142: error: ‘method’ undeclared (first use in this function)
ruby_debug.c:143: warning: implicit declaration of function ‘rb_method_entry’
ruby_debug.c: In function ‘debug_event_hook’:
ruby_debug.c:687: error: ‘rb_method_entry_t’ undeclared (first use in this function)
ruby_debug.c:687: error: ‘me’ undeclared (first use in this function)
make: *** [ruby_debug.o] Error 1


Gem files will remain installed in /usr/local/lib/ruby19/gems/1.9.1/gems/ruby-debug-base19-0.11.15 for inspection.
Results logged to /usr/local/lib/ruby19/gems/1.9.1/gems/ruby-debug-base19-0.11.15/ext/ruby_debug/gem_make.out