diff -r 563033aa998c -r 83284b289430 src/cx/array_list.h
--- a/src/cx/array_list.h	Sun Oct 12 20:21:56 2025 +0200
+++ b/src/cx/array_list.h	Wed Oct 15 22:45:21 2025 +0200
@@ -172,10 +172,9 @@
      * Reallocates space for the given array.
      *
      * Implementations are not required to free the original array.
-     * This allows reallocation of static memory by allocating heap memory
-     * and copying the array contents. The information in the custom fields of
-     * the referenced allocator can be used to track the state of the memory
-     * or to transport other additional data.
+     * This allows reallocation of static or stack memory by allocating heap memory
+     * and copying the array contents; namely when @c stack_ptr in this struct
+     * is not @c NULL and @p array equals @c stack_ptr.
      *
      * @param array the array to reallocate
      * @param old_capacity the old number of elements
@@ -196,21 +195,14 @@
     );
 
     /**
-     * Custom data pointer.
+     * The allocator that shall be used for the reallocations.
      */
-    void *ptr1;
-    /**
-     * Custom data pointer.
-     */
-    void *ptr2;
+    const CxAllocator *allocator;
     /**
-     * Custom data integer.
+     * Optional pointer to stack memory
+     * if the array is originally located on the stack.
      */
-    size_t int1;
-    /**
-     * Custom data integer.
-     */
-    size_t int2;
+    const void *stack_ptr;
 };
 
 /**
@@ -229,23 +221,23 @@
  *
  * When @p allocator is @c NULL, the cxDefaultAllocator will be used.
  *
- * When @p stackmem is not @c NULL, the reallocator is supposed to be used
- * @em only for the specific array initially located at @p stackmem.
+ * When @p stack_ptr is not @c NULL, the reallocator is supposed to be used
+ * @em only for the specific array initially located at @p stack_ptr.
  * When reallocation is needed, the reallocator checks if the array is
- * still located at @p stackmem and copies the contents to the heap.
+ * still located at @p stack_ptr and copies the contents to the heap.
  *
  * @note Invoking this function with both arguments being @c NULL will return a
  * reallocator that behaves like #cx_array_default_reallocator.
  *
  * @param allocator the allocator this reallocator shall be based on
- * @param stackmem the address of the array when the array is initially located
+ * @param stack_ptr the address of the array when the array is initially located
  * on the stack or shall not reallocate in place
  * @return an array reallocator
  */
 cx_attr_export
 CxArrayReallocator cx_array_reallocator(
         const struct cx_allocator_s *allocator,
-        const void *stackmem
+        const void *stack_ptr
 );
 
 /**