The below patch works around the issue that Allegro does not record the source file location for methods defined inside a defgeneric form. The idea is that if the source location of a method is not found, then the defgeneric form is almost certainly the right place. For example: (defgeneric foo (x) (:method ((x fixnum)) (/ 1 0))) Calling (foo 123) and hitting "v" in the traceback would result in "Unknown source location for (method common-lisp-user::foo)" but with the patch leads correctly to the defgeneric form. (For methods defined outside the defgeneric form, the source location recording works fine.) *** swank-allegro.lisp 10 Jun 2008 19:55:30 +0200 1.102 --- swank-allegro.lisp 10 Jun 2008 21:19:20 +0200 *************** *** 414,419 **** --- 414,426 ---- (fspec-definition-locations next))) (t (let ((defs (excl::find-source-file fspec))) + (when (and (null defs) + (listp fspec) + (string= (car fspec) '#:method)) + ;; If methods are defined in a defgeneric form, the source location is + ;; recorded for the gf but not for the methods. Therefore fall back to + ;; the gf as the likely place of definition. + (setq defs (excl::find-source-file (second fspec)))) (if (null defs) (list (list (list nil fspec)