fix(jumper): free registers on removal, skip dead markers, toggle back

Three defects in the saved-location store: removal shifted the slot vector but never freed the dropped register, and a later store allocated by next-index — a char a surviving slot still held — so it silently overwrote that slot's marker. jumper--with-marker-at also guarded only markerp, so a location whose buffer was killed made store and jump signal wrong-type errors. And the single-location toggle never returned: its already-there branch did nothing. Store now takes the first unused register char in the live slice, removal clears the freed register so its marker stops pinning the buffer, the marker guard checks buffer liveness so dead entries are skipped, and the toggle jumps to the last-location register when one is set.

1 files changed, 35 insertions, 10 deletions

diff --git a/modules/jumper.el b/modules/jumper.el
index de270de66..d5d0cf7a7 100644
--- a/modules/jumper.el
+++ b/modules/jumper.el
@@ -114,7 +114,8 @@ marker's buffer with point at the marker (within `save-current-buffer' and
 marker."
   (let* ((reg (aref jumper--registers index))
          (marker (get-register reg)))
-    (when (and marker (markerp marker))
+    (when (and marker (markerp marker)
+               (buffer-live-p (marker-buffer marker)))
       (save-current-buffer
         (set-buffer (marker-buffer marker))
         (save-excursion
@@ -156,6 +157,20 @@ Indices whose marker is no longer valid are skipped (their
            for fmt = (jumper--format-location i)
            when fmt collect (cons fmt i)))
 
+(defun jumper--first-free-register ()
+  "Return the lowest register char in 0..N-1 not held by a live slot.
+N is `jumper-max-locations'.  Only the live slice (indices 0 through
+`jumper--next-index' minus 1) is consulted, so a char freed by a removal is
+reused on the next store instead of colliding with a surviving slot's
+register and silently overwriting its marker."
+  (let ((used (make-hash-table :test 'eql)))
+    (dotimes (i jumper--next-index)
+      (let ((r (aref jumper--registers i)))
+        (when r (puthash r t used))))
+    (cl-loop for c from ?0 below (+ ?0 jumper-max-locations)
+             unless (gethash c used)
+             return c)))
+
 (defun jumper--do-store-location ()
   "Store current location in the next free register.
 Returns: \\='already-exists if location is already stored,
@@ -165,7 +180,7 @@ Returns: \\='already-exists if location is already stored,
    ((jumper--location-exists-p) 'already-exists)
    ((not (jumper--register-available-p)) 'no-space)
    (t
-    (let ((reg (+ ?0 jumper--next-index)))
+    (let ((reg (jumper--first-free-register)))
       (point-to-register reg)
       (aset jumper--registers jumper--next-index reg)
       (setq jumper--next-index (1+ jumper--next-index))
@@ -190,7 +205,13 @@ Returns: \\='no-locations if no locations stored,
    ;; Toggle behavior when target-idx is nil and only 1 location
    ((and (null target-idx) (= jumper--next-index 1))
     (if (jumper--location-exists-p)
-        'already-there
+        ;; Already at the only location: toggle back to where we came from
+        ;; when a last-location is recorded, otherwise report no movement.
+        (if (get-register jumper--last-location-register)
+            (progn
+              (jump-to-register jumper--last-location-register)
+              'jumped-back)
+          'already-there)
       (let ((reg (aref jumper--registers 0)))
         (point-to-register jumper--last-location-register)
         (jump-to-register reg)
@@ -217,6 +238,7 @@ Returns: \\='no-locations if no locations stored,
    ((= jumper--next-index 1)
     (pcase (jumper--do-jump-to-location nil)
       ('already-there (message "You're already at the stored location"))
+      ('jumped-back (message "Jumped back to previous location"))
       ('jumped (message "Jumped to location"))))
    ;; Multiple locations - prompt user
    (t
@@ -233,13 +255,16 @@ Returns: \\='no-locations if no locations stored,
       (message "Jumped to location")))))
 
 (defun jumper--reorder-registers (removed-idx)
-  "Reorder registers after removing the one at REMOVED-IDX."
-  (when (< removed-idx (1- jumper--next-index))
-	;; Shift all higher registers down
-	(cl-loop for i from removed-idx below (1- jumper--next-index)
-			 do (let ((next-reg (aref jumper--registers (1+ i))))
-				  (aset jumper--registers i next-reg))))
-  (setq jumper--next-index (1- jumper--next-index)))
+  "Reorder registers after removing the one at REMOVED-IDX.
+Shift the higher registers down and clear the freed register so its marker
+no longer pins its buffer."
+  (let ((freed (aref jumper--registers removed-idx)))
+    (when (< removed-idx (1- jumper--next-index))
+      ;; Shift all higher registers down
+      (cl-loop for i from removed-idx below (1- jumper--next-index)
+               do (aset jumper--registers i (aref jumper--registers (1+ i)))))
+    (setq jumper--next-index (1- jumper--next-index))
+    (when freed (set-register freed nil))))
 
 (defun jumper--do-remove-location (index)
   "Remove location at INDEX.