ERROR gem install rubysl-yaml --pre

gistfile1.txt

[root@host user]# gem install rubysl-yaml --pre
Building native extensions.  This could take a while...
ERROR:  Error installing rubysl-yaml:
	ERROR: Failed to build gem native extension.

    /usr/local/rvm/rubies/ruby-2.0.0-p247/bin/ruby extconf.rb
checking for st.h... yes
creating Makefile

make "DESTDIR="
compiling emitter.c
compiling node.c
compiling yaml2byte.c
compiling bytecode.c
compiling handler.c
compiling gram.c
compiling token.c
compiling implicit.c
compiling syck.c
compiling rubyext.c
rubyext.c: In function ‘mktime_do’:
rubyext.c:292: warning: unused variable ‘offset’
rubyext.c: In function ‘rb_syck_load_handler’:
rubyext.c:664: warning: implicit declaration of function ‘rb_hash_size’
rubyext.c: In function ‘rb_syck_err_handler’:
rubyext.c:684: warning: format ‘%d’ expects type ‘int’, but argument 5 has type ‘long int’
rubyext.c: In function ‘syck_const_find’:
rubyext.c:1047: warning: implicit declaration of function ‘rb_ary_size’
rubyext.c: In function ‘syck_scalar_value_set’:
rubyext.c:1481: error: ‘struct RString’ has no member named ‘ptr’
rubyext.c: In function ‘syck_node_type_id_set’:
rubyext.c:1741: error: ‘struct RString’ has no member named ‘ptr’
make: *** [rubyext.o] Error 1


Gem files will remain installed in /usr/local/rvm/gems/ruby-2.0.0-p247@cq-web/gems/rubysl-yaml-2.0.4 for inspection.
Results logged to /usr/local/rvm/gems/ruby-2.0.0-p247@cq-web/gems/rubysl-yaml-2.0.4/ext/rubysl/syck/gem_make.out