Ruby on Rails in Windows: Error in installing DevKit

I'm new in ROR and I'm trying to install DevKit but I get some errors. I use Win7-64bit and i installed DevKit-mingw64-64-4.7.2-20130224-1432-sfx. I followed the installation in github. Honestly, the errors are not clear and I can't find out what I should do to fix the problem.

 C:\Devkit>type config.yml This configuration file contains the absolute path locations of all installed Rubies to be enhanced to work with the DevKit. This config file is generated by the 'ruby dk.rb init' step and may be modified before running the 'ruby dk.rb install' step. To include any installed Rubies that were not automagically discovered, simply add a line below the triple hyphens with the absolute path to the Ruby root directory. Example: -- - C:/ruby19trunk - C:/ruby192dev -- c:/Ruby22 

then

C:\Devkit>ruby dk.rb install [INFO] Skipping existing gem override for ' c:/Ruby22' [WARN] Skipping existing DevKit helper library for ' c:/Ruby22' 

and

C:\Devkit>gem install json --platform=ruby Temporarily enhancing PATH to include DevKit... Building native extensions. This could take a while... ERROR: Error installing json: ERROR: Failed to build gem native extension. c:/Ruby22/bin/ruby.exe -r ./siteconf20150524-7692-son84q.rb extconf.rb creating Makefile make "DESTDIR=" clean make "DESTDIR=" generating generator-i386-mingw32.def compiling generator.c In file included from c:/Ruby22/include/ruby-2.2.0/ruby.h:33:0, from ../fbuffer/fbuffer.h:5, from generator.c:1: c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:111:14: error: size of array 'ruby_chec k_sizeof_voidp' is negative In file included from c:/Ruby22/include/ruby-2.2.0/ruby.h:33:0, from ../fbuffer/fbuffer.h:5, from generator.c:1: c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h: In function 'rb_obj_freeze_inline': c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1156:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1157:2: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1158:6: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1158:27: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h: In function 'rb_data_object_get': c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1192:13: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h: In function 'rb_obj_written': c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1271:10: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1271:34: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h: In function 'rb_num2char_inline': c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1344:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1344:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1344:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1344:36: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1344:36: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1344:36: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1345:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1345:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1345:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h: In function 'rb_class_of': c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1670:12: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h: In function 'rb_type': c:/Ruby22/include/ruby-2.2.0/ruby/ruby.h:1687:12: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] In file included from generator.c:1:0: ../fbuffer/fbuffer.h: In function 'fbuffer_append_str': ../fbuffer/fbuffer.h:127:25: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] ../fbuffer/fbuffer.h:127:25: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] ../fbuffer/fbuffer.h:127:25: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c: In function 'convert_UTF8_to_JSON_ASCII': generator.c:129:35: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:129:35: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:129:35: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:130:38: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:130:38: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:130:38: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c: In function 'convert_UTF8_to_JSON': generator.c:227:23: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:227:23: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:227:23: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:228:25: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:228:25: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:228:25: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c: In function 'cState_configure': generator.c:559:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:559:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:559:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:560:34: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:560:34: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:560:34: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:567:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:567:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:567:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:568:33: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:568:33: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:568:33: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:575:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:575:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:575:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:576:40: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:576:40: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:576:40: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:583:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:583:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:583:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:584:36: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:584:36: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:584:36: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:591:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:591:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:591:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:592:37: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:592:37: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:592:37: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c: In function 'set_state_ivars': generator.c:640:21: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:640:21: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:640:21: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:642:24: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:642:24: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:642:24: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c: In function 'generate_json_object': generator.c:727:20: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:727:20: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:727:20: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c: In function 'generate_json_array': generator.c:773:20: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:773:20: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:773:20: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c: In function 'isArrayOrObject': generator.c:930:23: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:930:23: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:930:23: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:931:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:931:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:931:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c: In function 'cState_indent_set': generator.c:1055:11: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1055:11: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1055:11: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1064:32: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1064:32: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1064:32: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c: In function 'cState_space_set': generator.c:1093:11: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1093:11: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1093:11: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1102:31: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1102:31: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1102:31: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c: In function 'cState_space_before_set': generator.c:1129:11: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1129:11: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1129:11: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1138:38: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1138:38: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1138:38: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c: In function 'cState_object_nl_set': generator.c:1167:11: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1167:11: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1167:11: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1175:35: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1175:35: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1175:35: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c: In function 'cState_array_nl_set': generator.c:1202:11: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1202:11: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1202:11: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1210:34: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1210:34: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] generator.c:1210:34: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] make: *** [generator.o] Error 1 make failed, exit code 2 Gem files will remain installed in c:/Ruby22/lib/ruby/gems/2.2.0/gems/json-1.8.2 for inspection. Results logged to c:/Ruby22/lib/ruby/gems/2.2.0/extensions/x86-mingw32/2.2.0/jso n-1.8.2/gem_make.out