diff -r efbd59642577 -r 49a284f61e8c ucx/linked_list.c
--- a/ucx/linked_list.c	Fri Apr 21 21:25:32 2023 +0200
+++ b/ucx/linked_list.c	Sun May 07 11:53:10 2023 +0200
@@ -56,7 +56,7 @@
     return (void *) cur;
 }
 
-size_t cx_linked_list_find(
+ssize_t cx_linked_list_find(
         void const *start,
         ptrdiff_t loc_advance,
         ptrdiff_t loc_data,
@@ -69,7 +69,7 @@
     assert(cmp_func);
 
     void const *node = start;
-    size_t index = 0;
+    ssize_t index = 0;
     do {
         void *current = ll_data(node);
         if (cmp_func(current, elem) == 0) {
@@ -78,7 +78,7 @@
         node = ll_advance(node);
         index++;
     } while (node != NULL);
-    return index;
+    return -1;
 }
 
 void *cx_linked_list_first(
@@ -355,6 +355,9 @@
     // set start node
     ls = *begin;
 
+    // early exit when this list is empty
+    if (ls == NULL) return;
+
     // check how many elements are already sorted
     lc = ls;
     size_t ln = 1;
@@ -729,7 +732,7 @@
     return node == NULL ? NULL : node->payload;
 }
 
-static size_t cx_ll_find(
+static ssize_t cx_ll_find(
         struct cx_list_s const *list,
         void const *elem
 ) {