From bbcfac20a69bbd2af8d46cc498116b0b4798262d Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 26 Mar 2025 11:18:40 -0400
Subject: [PATCH 1/2] prioq: invalidate index pointers on removal

---
 src/basic/prioq.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/basic/prioq.c b/src/basic/prioq.c
index b3cf88ecad..194bd5e7eb 100644
--- a/src/basic/prioq.c
+++ b/src/basic/prioq.c
@@ -46,6 +46,11 @@ Prioq* prioq_free(Prioq *q) {
         if (!q)
                 return NULL;
 
+        /* Invalidate the index fields of any remaining objects */
+        FOREACH_ARRAY(item, q->items, q->n_items)
+                if (item->idx)
+                        *(item->idx) = PRIOQ_IDX_NULL;
+
         free(q->items);
         return mfree(q);
 }
@@ -178,6 +183,11 @@ static void remove_item(Prioq *q, struct prioq_item *i) {
         assert(q);
         assert(i);
 
+        /* Let's invalidate the index pointer stored in the user's object to indicate the item is now removed
+         * from the priority queue */
+        if (i->idx)
+                *(i->idx) = PRIOQ_IDX_NULL;
+
         l = q->items + q->n_items - 1;
 
         if (i == l)

From 39ce0324f94b928dae1889736a3638ee4a470aa9 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 26 Mar 2025 11:19:05 -0400
Subject: [PATCH 2/2] prioq: add some minor overflow checking assert()s

---
 src/basic/prioq.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/basic/prioq.c b/src/basic/prioq.c
index 194bd5e7eb..b3fec89f76 100644
--- a/src/basic/prioq.c
+++ b/src/basic/prioq.c
@@ -199,6 +199,7 @@ static void remove_item(Prioq *q, struct prioq_item *i) {
                 /* Not last entry, let's replace the last entry with
                  * this one, and reshuffle */
 
+                assert(i >= q->items);
                 k = i - q->items;
 
                 i->data = l->data;
@@ -262,6 +263,7 @@ void prioq_reshuffle(Prioq *q, void *data, unsigned *idx) {
         if (!i)
                 return;
 
+        assert(i >= q->items);
         k = i - q->items;
         k = shuffle_down(q, k);
         shuffle_up(q, k);