kc3-lang/kc3

diff --git a/libc3/facts_cursor.c b/libc3/facts_cursor.c
index 2f542c1..979531e 100644
--- a/libc3/facts_cursor.c
+++ b/libc3/facts_cursor.c
@@ -33,7 +33,8 @@ s_facts_cursor * facts_cursor_init (s_facts *facts,
   assert(cursor);
   assert(index);
   pred = skiplist_pred__fact(index, start);
-  assert(pred);
+  if (! pred)
+    return NULL;
   cursor->index = index;
   cursor->node = SKIPLIST_NODE_NEXT__fact(pred, 0);
   skiplist_node_delete__fact(pred);
@@ -55,7 +56,10 @@ s_facts_cursor * facts_cursor_init (s_facts *facts,
   cursor->var_predicate = NULL;
   cursor->var_object    = NULL;
   cursor->facts = facts;
-  facts_cursor_lock_init(cursor);
+  if (! facts_cursor_lock_init(cursor)) {
+    facts_cursor_clean(cursor);
+    return NULL;
+  }
   return cursor;
 }
 
diff --git a/libc3/skiplist.c.in b/libc3/skiplist.c.in
index 24d5356..92d0ff2 100644
--- a/libc3/skiplist.c.in
+++ b/libc3/skiplist.c.in
@@ -170,8 +170,9 @@ skiplist_pred___NAME$ (s_skiplist___NAME$ *skiplist, _TYPE$ _NAME$)
   assert(skiplist);
   level = skiplist->max_height;
   pred = skiplist_node_new___NAME$(NULL, skiplist->max_height);
+  if (! pred)
+    return NULL;
   node = skiplist->head;
-  assert(pred);
   while (level--) {
     n = node;
     while (n && skiplist->compare(_NAME$, n->_NAME$) > 0) {
diff --git a/libc3/skiplist__fact.c b/libc3/skiplist__fact.c
index 9b59ff9..32b4994 100644
--- a/libc3/skiplist__fact.c
+++ b/libc3/skiplist__fact.c
@@ -170,8 +170,9 @@ skiplist_pred__fact (s_skiplist__fact *skiplist, s_fact * fact)
   assert(skiplist);
   level = skiplist->max_height;
   pred = skiplist_node_new__fact(NULL, skiplist->max_height);
+  if (! pred)
+    return NULL;
   node = skiplist->head;
-  assert(pred);
   while (level--) {
     n = node;
     while (n && skiplist->compare(fact, n->fact) > 0) {