安装cocopods时出现错误

Building native extensions.  This could take a while...

ERROR:  Error installing cocoapods:

ERROR: Failed to build gem native extension.

current directory: /Users/caoshuaikun/.rvm/rubies/ruby-2.4.0/lib/ruby/gems/2.4.0/gems/json-1.8.3/ext/json/ext/generator

/Users/caoshuaikun/.rvm/rubies/ruby-2.4.0/bin/ruby -r ./siteconf20170103-1954-1elbc8h.rb extconf.rb

creating Makefile

current directory: /Users/caoshuaikun/.rvm/rubies/ruby-2.4.0/lib/ruby/gems/2.4.0/gems/json-1.8.3/ext/json/ext/generator

make "DESTDIR=" clean

current directory: /Users/caoshuaikun/.rvm/rubies/ruby-2.4.0/lib/ruby/gems/2.4.0/gems/json-1.8.3/ext/json/ext/generator

make "DESTDIR="

compiling generator.c

generator.c:861:25: error: use of undeclared identifier 'rb_cFixnum'

} else if (klass == rb_cFixnum) {

^

generator.c:863:25: error: use of undeclared identifier 'rb_cBignum'

} else if (klass == rb_cBignum) {

事了好多办法也没法解决,不知道这是几个意思,有大神帮忙解决一下么,求答案啊