Gemfile

# A sample Gemfile
source "https://rubygems.org"

gem 'ruby-prof'

output.log

[arthurnn@snowball test_bundler]$ RUBYOPT='--disable-gems' ruby /Users/arthurnn/.gem/ruby/2.3.0/bin/bundle
Fetching gem metadata from https://rubygems.org/..
Fetching version metadata from https://rubygems.org/.
Resolving dependencies...
Using bundler 1.11.2
Installing ruby-prof 0.15.9 with native extensions

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    current directory: /Users/arthurnn/.gem/ruby/2.3.0/gems/ruby-prof-0.15.9/ext/ruby_prof
/Users/arthurnn/.rubies/ruby-2.3.0/bin/ruby -r ./siteconf20160502-93658-1kd37yw.rb extconf.rb
checking for rb_gc_stat()... yes
checking for rb_gc_count()... yes
checking for rb_os_allocated_objects()... no
checking for rb_gc_allocated_size()... no
checking for rb_gc_collections()... no
checking for rb_gc_time()... no
checking for rb_gc_total_time()... no
checking for rb_gc_total_mallocs()... no
checking for rb_gc_total_malloced_bytes()... no
checking for rb_heap_total_mem()... no
checking for rb_gc_heap_info()... no
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:
	--with-opt-dir
	--with-opt-include
	--without-opt-include=${opt-dir}/include
	--with-opt-lib
	--without-opt-lib=${opt-dir}/lib
	--with-make-prog
	--without-make-prog
	--srcdir=.
	--curdir
	--ruby=/Users/arthurnn/.rubies/ruby-2.3.0/bin/$(RUBY_BASE_NAME)
extconf.rb:41:in `<main>': uninitialized constant Gem (NameError)

To see why this extension failed to compile, please check the mkmf.log which can be found here:

  /Users/arthurnn/.gem/ruby/2.3.0/extensions/x86_64-darwin-15/2.3.0-static/ruby-prof-0.15.9/mkmf.log

extconf failed, exit code 1

Gem files will remain installed in /Users/arthurnn/.gem/ruby/2.3.0/gems/ruby-prof-0.15.9 for inspection.
Results logged to /Users/arthurnn/.gem/ruby/2.3.0/extensions/x86_64-darwin-15/2.3.0-static/ruby-prof-0.15.9/gem_make.out
An error occurred while installing ruby-prof (0.15.9), and Bundler cannot continue.
Make sure that `gem install ruby-prof -v '0.15.9'` succeeds before bundling.