# HG changeset patch
# User Mike Becker <universe@uap-core.de>
# Date 1764513675 -3600
# Node ID 313fd460d264a69aa172c285c44513790f630c30
# Parent  3ee5a5c7823ac6a270637dec71cd35c207dca924
fix missing memory alignment for linked list node extra data

diff -r 3ee5a5c7823a -r 313fd460d264 src/cx/linked_list.h
--- a/src/cx/linked_list.h	Sun Nov 30 15:06:02 2025 +0100
+++ b/src/cx/linked_list.h	Sun Nov 30 15:41:15 2025 +0100
@@ -62,7 +62,14 @@
      */
     off_t loc_data;
     /**
+     * Location of extra data (optional).
+     * Negative when no extra data is requested.
+     * @see cx_linked_list_extra_data()
+     */
+    off_t loc_extra;
+    /**
      * Additional bytes to allocate @em behind the payload (e.g. for metadata).
+     * @see cx_linked_list_extra_data()
      */
     size_t extra_data_len;
     /**
@@ -112,6 +119,23 @@
         cxLinkedListCreate(NULL, NULL, elem_size)
 
 /**
+ * Instructs the linked list to reserve extra data in each node.
+ *
+ * The extra data will be aligned and placed behind the element data.
+ * The exact location in the node is stored in the @c loc_extra field
+ * of the linked list.
+ *
+ * You should usually not use this function except when you are creating an
+ * own linked-list implementation that is based on the UCX linked list and
+ * needs to store extra data in each node.
+ *
+ * @param list the list (must be a linked list)
+ * @param len the length of the extra data
+ */
+cx_attr_nonnull
+CX_EXPORT void cx_linked_list_extra_data(cx_linked_list *list, size_t len);
+
+/**
  * Finds the node at a certain index.
  *
  * This function can be used to start at an arbitrary position within the list.
diff -r 3ee5a5c7823a -r 313fd460d264 src/kv_list.c
--- a/src/kv_list.c	Sun Nov 30 15:06:02 2025 +0100
+++ b/src/kv_list.c	Sun Nov 30 15:41:15 2025 +0100
@@ -98,7 +98,7 @@
 }
 
 static CxHashKey *cx_kv_list_loc_key(cx_kv_list *list, void *node_data) {
-    return (CxHashKey*)((char*)node_data + list->list.base.collection.elem_size);
+    return (CxHashKey*)((char*)node_data - list->list.loc_data + list->list.loc_extra);
 }
 
 static void cx_kvl_deallocate(struct cx_list_s *list) {
@@ -559,7 +559,7 @@
     CxList *list = cxLinkedListCreate(allocator, comparator, elem_size);
     if (list == NULL) return NULL; // LCOV_EXCL_LINE
     cx_linked_list *ll = (cx_linked_list*)list;
-    ll->extra_data_len = sizeof(CxHashKey);
+    cx_linked_list_extra_data(ll, sizeof(CxHashKey));
     CxMap *map = cxHashMapCreate(allocator, CX_STORE_POINTERS, 0);
     if (map == NULL) { // LCOV_EXCL_START
         cxListFree(list);
diff -r 3ee5a5c7823a -r 313fd460d264 src/linked_list.c
--- a/src/linked_list.c	Sun Nov 30 15:06:02 2025 +0100
+++ b/src/linked_list.c	Sun Nov 30 15:41:15 2025 +0100
@@ -692,8 +692,13 @@
 }
 
 static void *cx_ll_malloc_node(const cx_linked_list *list) {
-    return cxZalloc(list->base.collection.allocator,
-                    list->loc_data + list->base.collection.elem_size + list->extra_data_len);
+    size_t n;
+    if (list->extra_data_len == 0) {
+        n = list->loc_data + list->base.collection.elem_size;
+    } else {
+        n = list->loc_extra + list->extra_data_len;
+    }
+    return cxZalloc(list->base.collection.allocator, n);
 }
 
 static int cx_ll_insert_at(
@@ -1267,12 +1272,22 @@
 
     cx_linked_list *list = cxCalloc(allocator, 1, sizeof(cx_linked_list));
     if (list == NULL) return NULL;
-    list->extra_data_len = 0;
     list->loc_prev = 0;
     list->loc_next = sizeof(void*);
     list->loc_data = sizeof(void*)*2;
+    list->loc_extra = -1;
+    list->extra_data_len = 0;
     cx_list_init((CxList*)list, &cx_linked_list_class,
             allocator, comparator, elem_size);
 
     return (CxList *) list;
 }
+
+void cx_linked_list_extra_data(cx_linked_list *list, size_t len) {
+    list->extra_data_len = len;
+
+    off_t loc_extra = list->loc_data + list->base.collection.elem_size;
+    size_t alignment = alignof(void*);
+    size_t padding = alignment - (loc_extra % alignment);
+    list->loc_extra = loc_extra + padding;
+}