title: Error in installing json 1.8.3 with ruby 2.4.0 on Ubuntu
body: <p>I am trying to run an open source web app on my local machine(Ubuntu 15.10). When I run <code>bundle</code> command I'm getting this</p>
  
  <pre><code>Gem::Ext::BuildError: ERROR: Failed to build gem native extension.
  
  current directory:
  /home/yesh/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/json-1.8.3/ext/json/ext/generator
  /home/yesh/.rbenv/versions/2.4.0/bin/ruby -r ./siteconf20170310-4319-tlc92v.rb
  extconf.rb
  creating Makefile
  
  current directory:
  /home/yesh/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/json-1.8.3/ext/json/ext/generator
  make "DESTDIR=" clean
  
  current directory:
  /home/yesh/.rbenv/versions/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: In function ‘generate_json’:
  generator.c:861:25: error: ‘rb_cFixnum’ undeclared (first use in this function)
       } else if (klass == rb_cFixnum) {
                           ^
  generator.c:861:25: note: each undeclared identifier is reported only once for
  each function it appears in
  generator.c:863:25: error: ‘rb_cBignum’ undeclared (first use in this function)
       } else if (klass == rb_cBignum) {
                           ^
  generator.c: At top level:
  cc1: warning: unrecognized command line option ‘-Wno-self-assign’
  cc1: warning: unrecognized command line option ‘-Wno-constant-logical-operand’
  cc1: warning: unrecognized command line option ‘-Wno-parentheses-equality’
  cc1: warning: unrecognized command line option ‘-Wno-tautological-compare’
  Makefile:241: recipe for target 'generator.o' failed
  make: *** [generator.o] Error 1
  
  make failed, exit code 2
  
  Gem files will remain installed in
  /home/yesh/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/json-1.8.3 for
  inspection.
  Results logged to
  /home/yesh/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/extensions/x86_64-linux/2.4.0-static/json-1.8.3/gem_make.out
  
  An error occurred while installing json (1.8.3), and Bundler cannot
  continue.
  Make sure that `gem install json -v '1.8.3'` succeeds before bundling.
  </code></pre>
  
  <p>So I tried <code>gem install json -v '1.8.3'</code> but again got the same error message as above. Please help in resolving this.</p>