Error installing gems that use native extensions on Ubuntu, Ruby 1.9.2 via RVM

Question

I get an error while trying to install the ffi gem:

~ - 16:54>gem i ffi
Building native extensions.  This could take a while...
ERROR:  Error installing ffi:
        ERROR: Failed to build gem native extension.

        rake RUBYARCHDIR=/home/mdemare/.rvm/gems/ruby-1.9.2-p136/gems/ffi-1.0.6/lib RUBYLIBDIR=/home/mdemare/.rvm/gems/ruby-1.9.2-p136/gems/ffi-1.0.6/lib
/home/mdemare/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/site_ruby/1.9.1/rubygems.rb:370:in `bin_path': can't find gem rake ([">= 0"]) with executable rake (Gem::GemNotFoundException)
        from /home/mdemare/.rvm/gems/ruby-1.9.2-p136/bin/rake:19:in `<main>'

Gem files will remain installed in /home/mdemare/.rvm/gems/ruby-1.9.2-p136/gems/ffi-1.0.6 for inspection.
Results logged to /home/mdemare/.rvm/gems/ruby-1.9.2-p136/gems/ffi-1.0.6/gen/gem_make.out

I'm getting frequent errors of all kinds while installing gems with native extensions, so I assume that there's something broken with my Ubuntu installation, but I've no idea what. I'll post any information you need to diagnose the problem.

EDIT: When I cd to the ffi gem (mentioned in the second but last line), and run the rake line in line 6, I get "Could not find RubyGem rake-compiler".

After gem i rake-compiler, and run rake again, I get this:

configure: error: source directory already configured; run "make distclean" there first
make: *** [/home/mdemare/.rvm/gems/ruby-1.9.2-p136/gems/ffi-1.0.6/build/x86_64-linux/ffi_c/1.9.2/libffi/.libs/libffi_convenience.a] Error 1
rake aborted!
Command failed with status (2): [make...]

Update:

These are my rake gemspecs:

~ - 10:59>find ~/.rvm/ -name 'rake-0.8.7.gemspec'
~/.rvm/gems/ruby-1.9.2-p136/specifications/rake-0.8.7.gemspec
~/.rvm/gems/ruby-1.9.2-p136@global/specifications/rake-0.8.7.gemspec
~/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/gems/1.9.1/specifications/rake-0.8.7.gemspec

The last one is where gem looks, but that gemspec is different from the first one, and doesn't include the executable. Copying the long one doesn't quite solve the problem though - I get a file not found for the rake executable.

Answer 1

This caused me a ton of aggravation at the Boston Hack Day when trying to install Vagrant (for which FFI is a dependency). I ended up wasting so much time that I switched machines to work around the problem.

After the fact, I found a hack that works (although I'm sure there's a better solution). The file that the error message is complaining about

~/.rvm/gems/ruby-1.9.2-p180/bin/rake

differs from other similar copies in that it's missing path setup stuff at the head, so I copied these lines from one of the files that had them:

[genericized per @danv's answer below. Thanks for the improvement!]

ENV['GEM_HOME']=ENV['GEM_HOME'] || '~/.rvm/gems/ruby-1.9.2-p180'
ENV['GEM_PATH']=ENV['GEM_PATH'] || '~/.rvm/gems/ruby-1.9.2-p180:~/.rvm/gems/ruby-1.9.2-p180@global'
ENV['PATH']='~/.rvm/gems/ruby-1.9.2-p180/bin:~/.rvm/gems/ruby-1.9.2-p180@global/bin:~/.rvm/rubies/ruby-1.9.2-p180/bin:' + ENV['PATH']

That fixed it for me. This was a new Ubuntu 10.10 install with no default Ruby installation (which could be part of the problem) and Ruby 1.9.2 installed using RVM. Lots of other gems installed fine, including those requiring native compilation, so the problem is something specific to FFI.

Answer 2

I had a similar problem, and a workaround at http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=529663 helped me. In short, try to install the gem with: $ rake=/usr/bin/rake gem install ffi