Add backwards compatibility define_singleton_method for Ruby 1.8.

lib/process_shared.rb

@@ -1,6 +1,25 @@
 require 'ffi'
 
+if VERSION =~ /^1.8/
+  require 'process_shared/define_singleton_method'
+  
+  module ProcessShared
+    module PSem
+      extend DefineSingletonMethod
+    end
+
+    module RT
+      extend DefineSingletonMethod
+    end
+
+    module LibC
+      extend DefineSingletonMethod
+    end
+  end
+end
+
 require 'process_shared/semaphore'
 require 'process_shared/bounded_semaphore'
 require 'process_shared/mutex'
 require 'process_shared/shared_memory'
+

lib/process_shared/define_singleton_method.rb

@@ -0,0 +1,14 @@
+module ProcessShared
+  module DefineSingletonMethod
+    # This method was added in Ruby 1.9.x.  Include this module for
+    # backwards compatibility.
+    #
+    # This isn't exactly compatible with the method in 1.9 which can
+    # take a Proc, Method, or a block.  This only accepts a block.
+    def define_singleton_method(sym, &block)
+      eigenclass = class << self; self; end
+      eigenclass.send(:define_method, sym, &block)
+    end
+  end
+end
+