diff -r e77ccf1c4bb3 -r 4d58cbcc9efa ucx/cx/map.h
--- a/ucx/cx/map.h	Sun Dec 07 20:16:59 2025 +0100
+++ b/ucx/cx/map.h	Fri Dec 19 17:53:18 2025 +0100
@@ -183,9 +183,9 @@
      * Add or overwrite an element.
      * If the @p value is @c NULL, the implementation
      * shall only allocate memory instead of adding an existing value to the map.
-     * Returns a pointer to the allocated memory or @c NULL if allocation fails.
+     * Returns a map entry where the pointer to the key is @c NULL if allocation fails.
      */
-    void *(*put)(CxMap *map, CxHashKey key, void *value);
+    CxMapEntry (*put)(CxMap *map, CxHashKey key, void *value);
 
     /**
      * Returns an element.
@@ -357,8 +357,6 @@
  * @param map the map
  * @param key the key
  * @return the pointer to the allocated memory or @c NULL if allocation fails
- * @retval zero success
- * @retval non-zero value on memory allocation failure
  * @see cxMapEmplace()
  */
 cx_attr_nonnull
@@ -379,8 +377,6 @@
  * @param map (@c CxMap*) the map
  * @param key (any supported key type) the key
  * @return the pointer to the allocated memory or @c NULL if allocation fails
- * @retval zero success
- * @retval non-zero value on memory allocation failure
  * @see CX_HASH_KEY()
  */
 #define cxMapEmplace(map, key) cx_map_emplace(map, CX_HASH_KEY(key))
@@ -603,6 +599,139 @@
 CX_EXPORT int cxMapUnion(CxMap *dst, const CxMap *src,
         cx_clone_func clone_func, const CxAllocator *clone_allocator, void *data);
 
+/**
+ * Performs a shallow clone of one map into another.
+ *
+ * This function uses the default allocator, if needed, and performs
+ * shallow clones with @c memcpy().
+ *
+ * If the destination map already contains entries, the cloned entries
+ * are added to that map, possibly overwriting existing elements when
+ * the keys already exist.
+ *
+ * When elements in the destination map need to be replaced, any destructor
+ * function is called on the replaced elements before replacing them.
+ *
+ * @attention If the cloned elements need to be destroyed by a destructor
+ * function, you must make sure that the destination map also uses this
+ * destructor function.
+ *
+ * @param dst the destination map
+ * @param src the source map
+ * @retval zero when all elements were successfully cloned
+ * @retval non-zero when an allocation error occurred
+ * @see cxMapClone()
+ */
+cx_attr_nonnull
+CX_EXPORT int cxMapCloneShallow(CxMap *dst, const CxMap *src);
+
+/**
+ * Clones entries of a map if their key is not present in another map.
+ *
+ * This function uses the default allocator, if needed, and performs
+ * shallow clones with @c memcpy().
+ *
+ * @param dst the destination map
+ * @param minuend the map to subtract the entries from
+ * @param subtrahend the map containing the elements to be subtracted
+ * @retval zero when the elements were successfully cloned
+ * @retval non-zero when an allocation error occurred
+ */
+cx_attr_nonnull
+CX_EXPORT int cxMapDifferenceShallow(CxMap *dst, const CxMap *minuend, const CxMap *subtrahend);
+
+/**
+ * Clones entries of a map if their key is not present in a list.
+ *
+ * This function uses the default allocator, if needed, and performs
+ * shallow clones with @c memcpy().
+ *
+ * Note that the list must contain keys of type @c CxKey
+ * (or pointers to such keys) and must use @c cx_hash_key_cmp
+ * as the compare function.
+ * Generic key types cannot be processed in this case.
+ *
+ * @param dst the destination map
+ * @param src the source map
+ * @param keys the list of @c CxKey items
+ * @retval zero when the elements were successfully cloned
+ * @retval non-zero when an allocation error occurred
+ * @see cxMapListDifference()
+ */
+cx_attr_nonnull
+CX_EXPORT int cxMapListDifferenceShallow(CxMap *dst, const CxMap *src, const CxList *keys);
+
+
+/**
+ * Clones entries of a map only if their key is present in another map.
+ *
+ * This function uses the default allocator, if needed, and performs
+ * shallow clones with @c memcpy().
+ *
+ * @param dst the destination map
+ * @param src the map to clone the entries from
+ * @param other the map to check for existence of the keys
+ * @retval zero when the elements were successfully cloned
+ * @retval non-zero when an allocation error occurred
+ */
+cx_attr_nonnull
+CX_EXPORT int cxMapIntersectionShallow(CxMap *dst, const CxMap *src, const CxMap *other);
+
+/**
+ * Clones entries of a map only if their key is present in a list.
+ *
+ * This function uses the default allocator, if needed, and performs
+ * shallow clones with @c memcpy().
+ *
+ * Note that the list must contain keys of type @c CxKey
+ * (or pointers to such keys) and must use @c cx_hash_key_cmp
+ * as the compare function.
+ * Generic key types cannot be processed in this case.
+ *
+ * @param dst the destination map
+ * @param src the source map
+ * @param keys the list of @c CxKey items
+ * @retval zero when the elements were successfully cloned
+ * @retval non-zero when an allocation error occurred
+ */
+cx_attr_nonnull
+CX_EXPORT int cxMapListIntersectionShallow(CxMap *dst, const CxMap *src, const CxList *keys);
+
+/**
+ * Clones entries into a map if their key does not exist yet.
+ *
+ * This function uses the default allocator, if needed, and performs
+ * shallow clones with @c memcpy().
+ *
+ * If you want to calculate the union of two maps into a fresh new map,
+ * you can proceed as follows:
+ * 1. Clone the first map into a fresh, empty map.
+ * 2. Use this function to clone the second map into the result from step 1.
+ *
+ * @param dst the destination map
+ * @param src the map to clone the entries from
+ * @retval zero when the elements were successfully cloned
+ * @retval non-zero when an allocation error occurred
+ */
+cx_attr_nonnull
+CX_EXPORT int cxMapUnionShallow(CxMap *dst, const CxMap *src);
+
+
+/**
+ * Compares the entries of two maps.
+ *
+ * @param map the map
+ * @param other the other map that the first map is compared to
+ * @retval zero when both maps have the same key sets
+ * and the values are pairwise equivalent
+ * @retval negative when the first @p map has fewer keys than the @p other map
+ * @retval positive when the first @p map has more keys than the @p other map
+ * @retval non-zero (unspecified whether positive or negative) when the size
+ * of both maps is equal but a key or a value is different
+ */
+cx_attr_nonnull
+CX_EXPORT int cxMapCompare(const CxMap *map, const CxMap *other);
+
 #ifdef    __cplusplus
 } // extern "C"
 #endif