Trying to get FFI to work

gistfile1.txt

$ gcc -dynamiclib -o libsimplemath.dylib simple_math.c 
$ ruby ruby_ffi.rb
243.0
9.0
3628800

$ cc -m64 -dynamiclib -install_name libsimplemath.dylib -o libsimplemath.dylib simple_math.c
$ jruby -v ruby_ffi.rb jruby 1.2.0 (ruby 1.8.6 patchlevel 287) (2009-02-03 rev 8978) [x86_64-java]
243.0
9.0
3628800

$ cc -dynamiclib -install_name libsimplemath.dylib -o libsimplemath.dylib simple_math.c
$ jruby -v ruby_ffi.rb jruby 1.2.0 (ruby 1.8.6 patchlevel 287) (2009-02-03 rev 8978) [i386-java]
243.0
9.0
3628800

ruby_ffi.rb

# from http://www.igvita.com/2009/01/15/bridging-mri-jruby-rubinius-with-ffi/
require 'ffi'
 
class FFIMath
  extend FFI::Library
 
  # load our custom C library and attach
  # FFI functions to our Ruby runtime
  ffi_lib "simplemath"
 
  functions = [
    # method # parameters        # return
    [:power, [:double, :double], :double],
    [:square_root, [:double], :double],
    [:ffi_factorial, [:int], :long]
  ]
   
  functions.each do |func|
    begin
      attach_function(*func)
    rescue Object => e
      puts "Could not attach #{func.inspect}, #{e.message}"
    end
  end

	# attach_function :power, [:double, :double], :double
 
end
 
puts FFIMath.power(3,5)           # => 243.0
puts FFIMath.square_root(81)      # => 9.0
puts FFIMath.ffi_factorial(10)    # => 3628800

simple_math.c

/* from http://www.igvita.com/2009/01/15/bridging-mri-jruby-rubinius-with-ffi/ */
// Simple FFI example between C & Ruby
#include <math.h>
 
double power(double base, double power) {
  return pow(base, power);
}
 
double square_root(double x) {
  return sqrt(x);
}
 
// custom factorial function which we'll call from Ruby
 
long ffi_factorial(int max) {
  int i = max, result = 1;
  while (i >= 2) {
    result *= i--;
  }
  return result;
}