anchor.diff:  
   (in-package #:protobuf-system)
   
  +(eval-when (:compile-toplevel :load-toplevel :execute)
  +  (defparameter *protobuf-directory*
  +    "Directory containing the protobuf source code."
  +    (make-pathname :directory (pathname-directory *load-truename*))))
  +
  +(defun resolve-relative-pathname (pathname)
  +  "When PATHNAME doesn't have an absolute directory component, treat it as
  +relative to the protobuf source directory."
  +  (let ((directory (pathname-directory pathname)))
  +    (if (and (list directory) (eq (car directory) :absolute))
  +        pathname
  +        (merge-pathnames pathname *protobuf-directory*))))
  +
   
   ;;; Teach ASDF how to convert protocol buffer definition files into Lisp.
   
   
  -(defparameter *protoc* #p"google-protobuf/src/protoc"
  -   "Pathname of the protocol buffer compiler.")
  +(defparameter *protoc* (resolve-relative-pathname #p"google-protobuf/src/protoc")
  +  "Pathname of the protocol buffer compiler.")
   
   (defclass proto-file (cl-source-file)
     ((relative-proto-pathname
  
positive.code:     :initarg :proto-search-path
      :reader search-path
      :documentation "List containing directories in which the protocol buffer
  compiler should search for imported protobuf files."))
    (:documentation "A protocol buffer definition file."))
  
  (defclass proto-to-lisp (operation)
    ()
  
negative.code:    (:proto-file "unittest"
      :proto-pathname "google-protobuf/src/google/protobuf/unittest"
      :depends-on ("unittest_import")
      :proto-search-path (#p"google-protobuf/src/"))
     ))
  