Thread

1. dlist_check: add check for nodes pointing to themselves

   杨磊 <yanglei@halodbtech.com> — 2026-03-17T12:56:15Z

   Hi hackers,
   
   I accidentally called the function dlist_push_head consecutively on the same node, 
   inserting it into a doubly linked list, which caused an infinite loop. 
   After adding the compile parameter -DILIST_DEBUG, an infinite loop occurred in the dlist_check function, 
   revealing that the next pointer of the current node was pointing to itself. 
   I am attempting to fix this issue with the following patch.
   
   regards,
   Lei Yang

2. Re: dlist_check: add check for nodes pointing to themselves

   ylshiyu@126.com <ylshiyu@126.com> — 2026-04-08T15:46:59Z

   Currently, postgresql will enter an infinite loop when calling dlist_push_head the second time. 
   After applying this patch, it will report ERROR: doubly linked list is corrupted.
   
   test case:
   ./configure --enable-debug CFLAGS='-O0 -DILIST_DEBUG' --enable-cassert
   
   PG_FUNCTION_INFO_V1(test_dlist);
   Datum
   test_dlist(PG_FUNCTION_ARGS)
   {
   dlist_head head;
   dlist_node *n;
   
   n = palloc0(sizeof(dlist_node));
   dlist_init(&head);
   dlist_push_head(&head, n);
   dlist_push_head(&head, n);
   
   PG_RETURN_NULL();
   }
   
   
   
   
   
   regards,
   Lei Yang
    
   From: 杨磊
   Date: 2026-03-17 20:56
   To: pgsql-hackers
   Subject: dlist_check: add check for nodes pointing to themselves
   Hi hackers,
    
   I accidentally called the function dlist_push_head consecutively on the same node, 
   inserting it into a doubly linked list, which caused an infinite loop. 
   After adding the compile parameter -DILIST_DEBUG, an infinite loop occurred in the dlist_check function, 
   revealing that the next pointer of the current node was pointing to itself. 
   I am attempting to fix this issue with the following patch.
    
   regards,
   Lei Yang