> > > While I never install ffi this way, jruby+bundler on Win7 32bit with JRuby 
> > > 1.7.0 ended up in Wile E. flames trying to build the C ext due to my 
> > > scheming: 
> > >
> > > C:\Users\Jon\Downloads\temp\ffi-java>type Gemfile 
> > > source :rubygems 
> > > gem 'ffi', '1.2.0.pre6', :platforms => :jruby 
> > >
> > > C:\Users\Jon\Downloads\temp\ffi-java>bundle install 
> > > Fetching gem metadata from http://rubygems.org/........... 
> > > Fetching gem metadata from http://rubygems.org/.. 
> > > Installing ffi (1.2.0.pre6) with native extensions 
> > > Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native 
> > > extension. 

> > 
> >  
> > Hmm.  When installing on something that is not MRI, extconf.rb generates a 
> > dummy Makefile.  I suspect on win32, the dummy Makefile isn't quite 
> > correct.  Can you investigate this one a bit more (look right at the bottom 
> > of ext/ext_c/extconf.rb)?  It could be something as simple as \r\n vs \n 
> > line termination.
> > 
> > I can continue to publish the ffi-java gem, but, I want to get rid of it in 
> > the long term.

> 
> Likely just need this tweak at extconf.rb:59
> 
> -  File.open("Makefile", "w") do |mf|
> +  File.open("Makefile", "wb") do |mf|
> 
> I'll try it out a bit later.

While binary mode may turn out to be an issue, the bigger issue is the dummy Makefile. If a JRuby on Windows user doesn't have `make` on PATH...eeek.

Perhaps an alternative is to change from a extconf.rb to a Rakefile based extension:

  https://github.com/rubygems/rubygems/blob/master/lib/rubygems/installer.rb#L667-680
  https://github.com/rubygems/rubygems/blob/master/lib/rubygems/ext/rake_builder.rb#L22-36

I don't build native gems this way, but it looks like we could use the Rakefile to wrap 

  https://github.com/rubygems/rubygems/blob/master/lib/rubygems/ext/ext_conf_builder.rb#L12-21

since both `build` class methods take the same args, and both return a `results` Array.

A bit more complicated, but is there any scenario (regardless of platform) where a successful FFI gem install truly requires a JRuby user to have build tools on PATH?

Jon