(next-error): Handle zero and negative prefix args.

diff --git a/lisp/progmodes/compile.el b/lisp/progmodes/compile.el
index 1eef0ed..592eb7b 100644 (file)
--- a/lisp/progmodes/compile.el
+++ b/lisp/progmodes/compile.el
@@ -664,7 +664,7 @@ other kinds of prefix arguments are ignored."
 
   (next-error 1))
 
-(defun compilation-buffer-p (buffer)
+(defsubst compilation-buffer-p (buffer)
   (assq 'compilation-error-list (buffer-local-variables buffer)))
 
 ;; Return a compilation buffer.
@@ -724,7 +724,9 @@ See variables `compilation-parse-errors-function' and
                               ;; We want to pass a number here only if
                               ;; we got a numeric prefix arg, not just C-u.
                               (and (not (consp argp))
-                                   (1- (prefix-numeric-value argp))))
+                                   (if (< (prefix-numeric-value argp) 1)
+                                       0
+                                     (1- (prefix-numeric-value argp)))))
   ;; Make ARGP nil if the prefix arg was just C-u,
   ;; since that means to reparse the errors, which the
   ;; compile-reinitialize-errors call just did.
@@ -735,8 +737,21 @@ See variables `compilation-parse-errors-function' and
     (save-excursion
       (set-buffer compilation-last-buffer)
       ;; compilation-error-list points to the "current" error.
-      (setq next-errors (nthcdr (1- (prefix-numeric-value argp))
-                               compilation-error-list)
+      (setq next-errors 
+           (if (> (prefix-numeric-value argp) 0)
+               (nthcdr (1- (prefix-numeric-value argp))
+                       compilation-error-list)
+             ;; Zero or negative arg; we need to move back in the list.
+             (let ((n (1- (prefix-numeric-value argp)))
+                   (i 0)
+                   (e compilation-old-error-list))
+               ;; See how many cdrs away the current error is from the start.
+               (while (not (eq e compilation-error-list))
+                 (setq i (1+ i)
+                       e (cdr e)))
+               (if (> (- n) i)
+                   (error "Moved back past first error")
+                 (nthcdr (+ i n) compilation-old-error-list))))
            next-error (car next-errors))
       (while
          (progn