diff -r b60487c3ec36 -r af685cc9d623 ucx/cx/linked_list.h
--- a/ucx/cx/linked_list.h	Sun Aug 31 14:39:13 2025 +0200
+++ b/ucx/cx/linked_list.h	Sat Nov 08 23:06:11 2025 +0100
@@ -44,29 +44,55 @@
 #endif
 
 /**
+ * Metadata for a linked list.
+ */
+typedef struct cx_linked_list_s {
+    /** Base members. */
+    struct cx_list_s base;
+    /**
+     * Location of the prev pointer (mandatory).
+     */
+    off_t loc_prev;
+    /**
+     * Location of the next pointer (mandatory).
+     */
+    off_t loc_next;
+    /**
+     * Location of the payload (mandatory).
+     */
+    off_t loc_data;
+    /**
+     * Additional bytes to allocate @em behind the payload (e.g. for metadata).
+     */
+    size_t extra_data_len;
+    /**
+     * Pointer to the first node.
+     */
+    void *begin;
+    /**
+     * Pointer to the last node.
+     */
+    void *end;
+} cx_linked_list;
+
+/**
  * Allocates a linked list for storing elements with @p elem_size bytes each.
  *
  * If @p elem_size is #CX_STORE_POINTERS, the created list stores pointers instead of
- * copies of the added elements and the compare function will be automatically set
- * to cx_cmp_ptr(), if none is given.
+ * copies of the added elements, and the compare function will be automatically set
+ * to cx_cmp_ptr() if none is given.
  *
  * @param allocator the allocator for allocating the list nodes
- * (if @c NULL, a default stdlib allocator will be used)
+ * (if @c NULL, the cxDefaultAllocator will be used)
  * @param comparator the comparator for the elements
  * (if @c NULL, and the list is not storing pointers, sort and find
  * functions will not work)
  * @param elem_size the size of each element in bytes
  * @return the created list
  */
-cx_attr_nodiscard
-cx_attr_malloc
-cx_attr_dealloc(cxListFree, 1)
-cx_attr_export
-CxList *cxLinkedListCreate(
-        const CxAllocator *allocator,
-        cx_compare_func comparator,
-        size_t elem_size
-);
+cx_attr_nodiscard cx_attr_malloc cx_attr_dealloc(cxListFree, 1)
+CX_EXPORT CxList *cxLinkedListCreate(const CxAllocator *allocator,
+        cx_compare_func comparator, size_t elem_size);
 
 /**
  * Allocates a linked list for storing elements with @p elem_size bytes each.
@@ -76,25 +102,25 @@
  * after list creation or use cxLinkedListCreate().
  *
  * If @p elem_size is #CX_STORE_POINTERS, the created list stores pointers instead of
- * copies of the added elements and the compare function will be automatically set
- * to cx_cmp_ptr(), if none is given.
+ * copies of the added elements, and the compare function will be automatically set
+ * to cx_cmp_ptr().
  *
  * @param elem_size (@c size_t) the size of each element in bytes
  * @return (@c CxList*) the created list
  */
 #define cxLinkedListCreateSimple(elem_size) \
-    cxLinkedListCreate(NULL, NULL, elem_size)
+        cxLinkedListCreate(NULL, NULL, elem_size)
 
 /**
  * Finds the node at a certain index.
  *
  * This function can be used to start at an arbitrary position within the list.
- * If the search index is large than the start index, @p loc_advance must denote
- * the location of some sort of @c next pointer (i.e. a pointer to the next node).
+ * If the search index is larger than the start index, @p loc_advance must denote
+ * the location of a @c next pointer (i.e., a pointer to the next node).
  * But it is also possible that the search index is smaller than the start index
- * (e.g. in cases where traversing a list backwards is faster) in which case
- * @p loc_advance must denote the location of some sort of @c prev pointer
- * (i.e. a pointer to the previous node).
+ * (e.g., in cases where traversing a list backwards is faster).
+ * In that case @p loc_advance must denote the location of a @c prev pointer
+ * (i.e., a pointer to the previous node).
  *
  * @param start a pointer to the start node
  * @param start_index the start index
@@ -102,15 +128,9 @@
  * @param index the search index
  * @return the node found at the specified index
  */
-cx_attr_nonnull
-cx_attr_nodiscard
-cx_attr_export
-void *cx_linked_list_at(
-        const void *start,
-        size_t start_index,
-        ptrdiff_t loc_advance,
-        size_t index
-);
+cx_attr_nonnull cx_attr_nodiscard
+CX_EXPORT void *cx_linked_list_at(const void *start,size_t start_index,
+        ptrdiff_t loc_advance, size_t index);
 
 /**
  * Finds the node containing an element within a linked list.
@@ -122,18 +142,12 @@
  * @param elem a pointer to the element to find
  * @param found_index an optional pointer where the index of the found node
  * (given that @p start has index 0) is stored
- * @return the index of the element, if found - unspecified if not found
+ * @return a pointer to the found node or @c NULL if no matching node was found
  */
 cx_attr_nonnull_arg(1, 4, 5)
-cx_attr_export
-void *cx_linked_list_find(
-        const void *start,
-        ptrdiff_t loc_advance,
-        ptrdiff_t loc_data,
-        cx_compare_func cmp_func,
-        const void *elem,
-        size_t *found_index
-);
+CX_EXPORT void *cx_linked_list_find(const void *start, ptrdiff_t loc_advance,
+        ptrdiff_t loc_data, cx_compare_func cmp_func, const void *elem,
+        size_t *found_index);
 
 /**
  * Finds the first node in a linked list.
@@ -146,13 +160,8 @@
  * @param loc_prev the location of the @c prev pointer
  * @return a pointer to the first node
  */
-cx_attr_nonnull
-cx_attr_returns_nonnull
-cx_attr_export
-void *cx_linked_list_first(
-        const void *node,
-        ptrdiff_t loc_prev
-);
+cx_attr_nonnull cx_attr_returns_nonnull
+CX_EXPORT void *cx_linked_list_first(const void *node, ptrdiff_t loc_prev);
 
 /**
  * Finds the last node in a linked list.
@@ -165,13 +174,8 @@
  * @param loc_next the location of the @c next pointer
  * @return a pointer to the last node
  */
-cx_attr_nonnull
-cx_attr_returns_nonnull
-cx_attr_export
-void *cx_linked_list_last(
-        const void *node,
-        ptrdiff_t loc_next
-);
+cx_attr_nonnull cx_attr_returns_nonnull
+CX_EXPORT void *cx_linked_list_last(const void *node, ptrdiff_t loc_next);
 
 /**
  * Finds the predecessor of a node in case it is not linked.
@@ -184,16 +188,11 @@
  * @return the node or @c NULL if @p node has no predecessor
  */
 cx_attr_nonnull
-cx_attr_export
-void *cx_linked_list_prev(
-        const void *begin,
-        ptrdiff_t loc_next,
-        const void *node
-);
+CX_EXPORT void *cx_linked_list_prev(const void *begin, ptrdiff_t loc_next, const void *node);
 
 /**
  * Adds a new node to a linked list.
- * The node must not be part of any list already.
+ * The node must not be part of any list yet.
  *
  * @remark One of the pointers @p begin or @p end may be @c NULL, but not both.
  *
@@ -204,18 +203,11 @@
  * @param new_node a pointer to the node that shall be appended
  */
 cx_attr_nonnull_arg(5)
-cx_attr_export
-void cx_linked_list_add(
-        void **begin,
-        void **end,
-        ptrdiff_t loc_prev,
-        ptrdiff_t loc_next,
-        void *new_node
-);
+CX_EXPORT void cx_linked_list_add(void **begin, void **end, ptrdiff_t loc_prev, ptrdiff_t loc_next, void *new_node);
 
 /**
  * Prepends a new node to a linked list.
- * The node must not be part of any list already.
+ * The node must not be part of any list yet.
  *
  * @remark One of the pointers @p begin or @p end may be @c NULL, but not both.
  *
@@ -226,14 +218,7 @@
  * @param new_node a pointer to the node that shall be prepended
  */
 cx_attr_nonnull_arg(5)
-cx_attr_export
-void cx_linked_list_prepend(
-        void **begin,
-        void **end,
-        ptrdiff_t loc_prev,
-        ptrdiff_t loc_next,
-        void *new_node
-);
+CX_EXPORT void cx_linked_list_prepend(void **begin, void **end, ptrdiff_t loc_prev, ptrdiff_t loc_next, void *new_node);
 
 /**
  * Links two nodes.
@@ -244,13 +229,7 @@
  * @param loc_next the location of a @c next pointer within your node struct (required)
  */
 cx_attr_nonnull
-cx_attr_export
-void cx_linked_list_link(
-        void *left,
-        void *right,
-        ptrdiff_t loc_prev,
-        ptrdiff_t loc_next
-);
+CX_EXPORT void cx_linked_list_link(void *left, void *right, ptrdiff_t loc_prev, ptrdiff_t loc_next);
 
 /**
  * Unlinks two nodes.
@@ -263,17 +242,11 @@
  * @param loc_next the location of a @c next pointer within your node struct (required)
  */
 cx_attr_nonnull
-cx_attr_export
-void cx_linked_list_unlink(
-        void *left,
-        void *right,
-        ptrdiff_t loc_prev,
-        ptrdiff_t loc_next
-);
+CX_EXPORT void cx_linked_list_unlink(void *left, void *right, ptrdiff_t loc_prev, ptrdiff_t loc_next);
 
 /**
  * Inserts a new node after a given node of a linked list.
- * The new node must not be part of any list already.
+ * The new node must not be part of any list yet.
  *
  * @note If you specify @c NULL as the @p node to insert after, this function needs either the @p begin or
  * the @p end pointer to determine the start of the list. Then the new node will be prepended to the list.
@@ -286,19 +259,12 @@
  * @param new_node a pointer to the node that shall be inserted
  */
 cx_attr_nonnull_arg(6)
-cx_attr_export
-void cx_linked_list_insert(
-        void **begin,
-        void **end,
-        ptrdiff_t loc_prev,
-        ptrdiff_t loc_next,
-        void *node,
-        void *new_node
-);
+CX_EXPORT void cx_linked_list_insert(void **begin, void **end,
+        ptrdiff_t loc_prev, ptrdiff_t loc_next, void *node, void *new_node);
 
 /**
  * Inserts a chain of nodes after a given node of a linked list.
- * The chain must not be part of any list already.
+ * The chain must not be part of any list yet.
  *
  * If you do not explicitly specify the end of the chain, it will be determined by traversing
  * the @c next pointer.
@@ -317,20 +283,12 @@
  * @param insert_end a pointer to the last node of the chain (or NULL if the last node shall be determined)
  */
 cx_attr_nonnull_arg(6)
-cx_attr_export
-void cx_linked_list_insert_chain(
-        void **begin,
-        void **end,
-        ptrdiff_t loc_prev,
-        ptrdiff_t loc_next,
-        void *node,
-        void *insert_begin,
-        void *insert_end
-);
+CX_EXPORT void cx_linked_list_insert_chain(void **begin, void **end,
+        ptrdiff_t loc_prev, ptrdiff_t loc_next, void *node, void *insert_begin, void *insert_end);
 
 /**
  * Inserts a node into a sorted linked list.
- * The new node must not be part of any list already.
+ * The new node must not be part of any list yet.
  *
  * If the list starting with the node pointed to by @p begin is not sorted
  * already, the behavior is undefined.
@@ -343,26 +301,19 @@
  * @param cmp_func a compare function that will receive the node pointers
  */
 cx_attr_nonnull_arg(1, 5, 6)
-cx_attr_export
-void cx_linked_list_insert_sorted(
-        void **begin,
-        void **end,
-        ptrdiff_t loc_prev,
-        ptrdiff_t loc_next,
-        void *new_node,
-        cx_compare_func cmp_func
-);
+CX_EXPORT void cx_linked_list_insert_sorted(void **begin, void **end,
+        ptrdiff_t loc_prev, ptrdiff_t loc_next, void *new_node, cx_compare_func cmp_func);
 
 /**
  * Inserts a chain of nodes into a sorted linked list.
- * The chain must not be part of any list already.
+ * The chain must not be part of any list yet.
  *
  * If either the list starting with the node pointed to by @p begin or the list
  * starting with @p insert_begin is not sorted, the behavior is undefined.
  *
  * @attention In contrast to cx_linked_list_insert_chain(), the source chain
  * will be broken and inserted into the target list so that the resulting list
- * will be sorted according to @p cmp_func. That means, each node in the source
+ * will be sorted according to @p cmp_func. That means each node in the source
  * chain may be re-linked with nodes from the target list.
  *
  * @param begin a pointer to the beginning node pointer (required)
@@ -373,27 +324,62 @@
  * @param cmp_func a compare function that will receive the node pointers
  */
 cx_attr_nonnull_arg(1, 5, 6)
-cx_attr_export
-void cx_linked_list_insert_sorted_chain(
-        void **begin,
-        void **end,
-        ptrdiff_t loc_prev,
-        ptrdiff_t loc_next,
-        void *insert_begin,
-        cx_compare_func cmp_func
-);
+CX_EXPORT void cx_linked_list_insert_sorted_chain(void **begin, void **end,
+        ptrdiff_t loc_prev, ptrdiff_t loc_next, void *insert_begin, cx_compare_func cmp_func);
+
+/**
+ * Inserts a node into a sorted linked list if no other node with the same value already exists.
+ * The new node must not be part of any list yet.
+ *
+ * If the list starting with the node pointed to by @p begin is not sorted
+ * already, the behavior is undefined.
+ *
+ * @param begin a pointer to the beginning node pointer (required)
+ * @param end a pointer to the end node pointer (if your list has one)
+ * @param loc_prev the location of a @c prev pointer within your node struct (negative if your struct does not have one)
+ * @param loc_next the location of a @c next pointer within your node struct (required)
+ * @param new_node a pointer to the node that shall be inserted
+ * @param cmp_func a compare function that will receive the node pointers
+ * @retval zero when the node was inserted
+ * @retval non-zero when a node with the same value already exists
+ */
+cx_attr_nonnull_arg(1, 5, 6)
+CX_EXPORT int cx_linked_list_insert_unique(void **begin, void **end,
+        ptrdiff_t loc_prev, ptrdiff_t loc_next, void *new_node, cx_compare_func cmp_func);
+
+/**
+ * Inserts a chain of nodes into a sorted linked list, avoiding duplicates.
+ * The chain must not be part of any list yet.
+ *
+ * If either the list starting with the node pointed to by @p begin or the list
+ * starting with @p insert_begin is not sorted, the behavior is undefined.
+ *
+ * @attention In contrast to cx_linked_list_insert_sorted(), not all nodes of the
+ * chain might be added. This function returns a new chain consisting of all the duplicates.
+ *
+ * @param begin a pointer to the beginning node pointer (required)
+ * @param end a pointer to the end node pointer (if your list has one)
+ * @param loc_prev the location of a @c prev pointer within your node struct (negative if your struct does not have one)
+ * @param loc_next the location of a @c next pointer within your node struct (required)
+ * @param insert_begin a pointer to the first node of the chain that shall be inserted
+ * @param cmp_func a compare function that will receive the node pointers
+ * @return a pointer to a new chain with all duplicates that were not inserted (or @c NULL when there were no duplicates)
+ */
+cx_attr_nonnull_arg(1, 5, 6) cx_attr_nodiscard
+CX_EXPORT void *cx_linked_list_insert_unique_chain(void **begin, void **end,
+        ptrdiff_t loc_prev, ptrdiff_t loc_next, void *insert_begin, cx_compare_func cmp_func);
 
 /**
  * Removes a chain of nodes from the linked list.
  *
- * If one of the nodes to remove is the beginning (resp. end) node of the list and if @p begin (resp. @p end)
+ * If one of the nodes to remove is the beginning (resp. end) node of the list, and if @p begin (resp. @p end)
  * addresses are provided, the pointers are adjusted accordingly.
  *
  * The following combinations of arguments are valid (more arguments are optional):
  * @li @p loc_next and @p loc_prev (ancestor node is determined by using the prev pointer, overall O(1) performance)
  * @li @p loc_next and @p begin (ancestor node is determined by list traversal, overall O(n) performance)
  *
- * @remark The @c next and @c prev pointers of the removed node are not cleared by this function and may still be used
+ * @remark The @c next and @c prev pointers of the removed chain are not cleared by this function and may still be used
  * to traverse to a former adjacent node in the list, or within the chain.
  *
  * @param begin a pointer to the beginning node pointer (optional)
@@ -405,20 +391,13 @@
  * @return the actual number of nodes that were removed (can be less when the list did not have enough nodes)
  */
 cx_attr_nonnull_arg(5)
-cx_attr_export
-size_t cx_linked_list_remove_chain(
-        void **begin,
-        void **end,
-        ptrdiff_t loc_prev,
-        ptrdiff_t loc_next,
-        void *node,
-        size_t num
-);
+CX_EXPORT size_t cx_linked_list_remove_chain(void **begin, void **end,
+        ptrdiff_t loc_prev, ptrdiff_t loc_next, void *node, size_t num);
 
 /**
  * Removes a node from the linked list.
  *
- * If the node to remove is the beginning (resp. end) node of the list and if @p begin (resp. @p end)
+ * If the node to remove is the beginning (resp. end) node of the list, and if @p begin (resp. @p end)
  * addresses are provided, the pointers are adjusted accordingly.
  *
  * The following combinations of arguments are valid (more arguments are optional):
@@ -435,15 +414,8 @@
  * @param node the node to remove
  */
 cx_attr_nonnull_arg(5)
-static inline void cx_linked_list_remove(
-        void **begin,
-        void **end,
-        ptrdiff_t loc_prev,
-        ptrdiff_t loc_next,
-        void *node
-) {
-    cx_linked_list_remove_chain(begin, end, loc_prev, loc_next, node, 1);
-}
+CX_EXPORT void cx_linked_list_remove(void **begin, void **end,
+        ptrdiff_t loc_prev, ptrdiff_t loc_next, void *node);
 
 /**
  * Determines the size of a linked list starting with @p node.
@@ -453,11 +425,7 @@
  * @return the size of the list or zero if @p node is @c NULL
  */
 cx_attr_nodiscard
-cx_attr_export
-size_t cx_linked_list_size(
-        const void *node,
-        ptrdiff_t loc_next
-);
+CX_EXPORT size_t cx_linked_list_size(const void *node, ptrdiff_t loc_next);
 
 /**
  * Sorts a linked list based on a comparison function.
@@ -482,21 +450,14 @@
  * @param cmp_func the compare function defining the sort order
  */
 cx_attr_nonnull_arg(1, 6)
-cx_attr_export
-void cx_linked_list_sort(
-        void **begin,
-        void **end,
-        ptrdiff_t loc_prev,
-        ptrdiff_t loc_next,
-        ptrdiff_t loc_data,
-        cx_compare_func cmp_func
-);
+CX_EXPORT void cx_linked_list_sort(void **begin, void **end,
+        ptrdiff_t loc_prev, ptrdiff_t loc_next, ptrdiff_t loc_data, cx_compare_func cmp_func);
 
 
 /**
  * Compares two lists element wise.
  *
- * @attention Both list must have the same structure.
+ * @attention Both lists must have the same structure.
  *
  * @param begin_left the beginning of the left list (@c NULL denotes an empty list)
  * @param begin_right the beginning of the right list  (@c NULL denotes an empty list)
@@ -507,14 +468,8 @@
  * right list, positive if the left list is larger than the right list, zero if both lists are equal.
  */
 cx_attr_nonnull_arg(5)
-cx_attr_export
-int cx_linked_list_compare(
-        const void *begin_left,
-        const void *begin_right,
-        ptrdiff_t loc_advance,
-        ptrdiff_t loc_data,
-        cx_compare_func cmp_func
-);
+CX_EXPORT int cx_linked_list_compare(const void *begin_left, const void *begin_right,
+        ptrdiff_t loc_advance, ptrdiff_t loc_data, cx_compare_func cmp_func);
 
 /**
  * Reverses the order of the nodes in a linked list.
@@ -525,13 +480,7 @@
  * @param loc_next the location of a @c next pointer within your node struct (required)
  */
 cx_attr_nonnull_arg(1)
-cx_attr_export
-void cx_linked_list_reverse(
-        void **begin,
-        void **end,
-        ptrdiff_t loc_prev,
-        ptrdiff_t loc_next
-);
+CX_EXPORT void cx_linked_list_reverse(void **begin, void **end, ptrdiff_t loc_prev, ptrdiff_t loc_next);
 
 #ifdef __cplusplus
 } // extern "C"