Error from Data_Wrap_Struct when class is inside a module

ruby-talk
1

I'm playing around with writing a ruby extension in C and I'm getting a "wrong argument type Class (expected Class) (TypeError)" error that appears to be coming from my Data_Wrap_Struct call.

Parred down C code:

VALUE Library_new(VALUE klass)
{
  my_struct* lib;
  VALUE new_inst;

  // C fuction to allocate and initialize lib
  init(lib);

  // create new ruby object around C structure (Library_free defined but not shown)
  new_inst = Data_Wrap_Struct(klass, 0, Library_free, lib);

  return new_inst;
}

void Init_extension() {
  VALUE classLibrary = Qnil;

  classLibrary = rb_define_class("Library", rb_cObject);
  rb_define_singleton_method(classLibrary, "new", Library_new, 0);
}

And in ruby:

require 'extension'

lib = Library.new

Now, in the process of debugging and trying to put in some debug statements, I have discovered that by adding the line:

printf("class is a: %s\n", STR2CSTR(rb_funcall(rb_funcall(klass,rb_intern("class"),0),rb_intern("to_s"),0)));

just before the Data_Wrap_Struct call, then I don't get the error and appear to have an initialized library. Why would calling the equivalent of a 'self.class.to_s' change anything? I'm running "ruby 1.8.7 (2010-12-23 patchlevel 330) [powerpc-darwin8]". Any help or suggestions are much appreciated.

Michael