codec: webvtt: fix recursive cleanup

no siblings were reclaimed on cleanup

regression by 150a7f5648

(cherry picked from commit 73861536c3)

modules/codec/webvtt/subsvtt.c

@@ -462,16 +462,14 @@ static void webvtt_domnode_AppendLast( webvtt_dom_node_t **pp_append,
     webvtt_domnode_AppendLast( (webvtt_dom_node_t **) a, (webvtt_dom_node_t *) b )
 
 
-static webvtt_dom_node_t *webvtt_domnode_DeleteNode( webvtt_dom_node_t *p_node )
+static void webvtt_domnode_DeleteNode( webvtt_dom_node_t *p_node )
 {
-    webvtt_dom_node_t *p_child = NULL;
     if( p_node->type == NODE_TAG )
     {
         webvtt_dom_tag_t *p_tag_node = (webvtt_dom_tag_t *) p_node;
         text_style_Delete( p_tag_node->p_cssstyle );
         free( p_tag_node->psz_attrs );
         free( p_tag_node->psz_tag );
-        p_child = p_tag_node->p_child;
     }
     else if( p_node->type == NODE_TEXT )
     {
@@ -484,30 +482,51 @@ static webvtt_dom_node_t *webvtt_domnode_DeleteNode( webvtt_dom_node_t *p_node )
         text_style_Delete( p_cue_node->p_cssstyle );
         webvtt_cue_settings_Clean( &p_cue_node->settings );
         free( p_cue_node->psz_id );
-        p_child = p_cue_node->p_child;
     }
     else if( p_node->type == NODE_REGION )
     {
         webvtt_region_t *p_region_node = (webvtt_region_t *)p_node;
         text_style_Delete( p_region_node->p_cssstyle );
         free( p_region_node->psz_id );
-        p_child = p_region_node->p_child;
     }
     free( p_node );
-    return p_child;
 }
 
+static webvtt_dom_node_t * webvtt_domnode_getFirstChild( webvtt_dom_node_t *p_node );
+
 static void webvtt_domnode_ChainDelete( webvtt_dom_node_t *p_node )
 {
+    vlc_array_t stack;
+    vlc_array_init( &stack );
+
     while( p_node )
     {
+        webvtt_dom_node_t *p_child = webvtt_domnode_getFirstChild( p_node );
         webvtt_dom_node_t *p_next = p_node->p_next;
-        webvtt_dom_node_t *p_child = webvtt_domnode_DeleteNode( p_node );
-        while ( p_child )
-            p_child = webvtt_domnode_DeleteNode( p_child );
+        /* delete current node, then go to child, and then siblings */
+        webvtt_domnode_DeleteNode( p_node );
+        p_node = p_child;
+        if( p_next )
+        {
+            if( p_child ) /* go to child, process sibling later */
+                vlc_array_append( &stack, p_next );
+            else
+                p_node = p_next;
+        }
 
-        p_node = p_next;
+        if( !p_node )
+        {
+            /* pop saved next node */
+            size_t idx = vlc_array_count( &stack );
+            if( idx )
+            {
+                p_node = vlc_array_item_at_index( &stack, idx - 1 );
+                vlc_array_remove( &stack, idx - 1 );
+            }
+        }
     }
+
+    vlc_array_clear( &stack );
 }
 
 static webvtt_dom_text_t * webvtt_dom_text_New( webvtt_dom_node_t *p_parent )