Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!1.eu.feeder.erje.net!eternal-september.org!feeder.eternal-september.org!mx02.eternal-september.org!.POSTED!not-for-mail
From: Ike Naar <ike@iceland.freeshell.org>
Newsgroups: comp.lang.c
Subject: Re: Linked lists, message passing
Date: Fri, 19 Jun 2015 06:51:15 +0000 (UTC)
Organization: A noiseless patient Spider
Lines: 33
Message-ID: <slrn3vfsmo7f16.kvv.ike@iceland.freeshell.org>
References: <mm03eu$tnt$1@speranza.aioe.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Injection-Date: Fri, 19 Jun 2015 06:51:15 +0000 (UTC)
Injection-Info: mx02.eternal-september.org; posting-host="0be15772a183805a7eecac7d41b73a46"; logging-data="26753"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX19m9I/Zrkcv43MwKTBShC6f"
User-Agent: slrn/0.9.9p1 (NetBSD)
Cancel-Lock: sha1:Jtf8Go9AZModqVWFLhioiCHN4yY=
Xref: csiph.com comp.lang.c:63570

On 2015-06-19, Morten W. Petersen <morphex@gmail.com> wrote:
> [...]
> https://github.com/morphex/smash_xml/blob/c7a6017a75021432dbdb52178800e15dd4bc0061/message.c
> [...]
> Do you see any obvious problems with what in the code above?

This part has a problem:

  struct message_linked_list *working_free = head;
  while (working_free) {
    printf("Free: %s\n", working_free->data);
    free(working_free);
    working_free = working_free->next;
  }

The statement

    working_free = working_free->next;

has undefined behaviour because the value of a pointer that refers to
space deallocated by the free() function is used.

One possible workaround would be

  struct message_linked_list *working_free = head;
  while (working_free) {
    printf("Free: %s\n", working_free->data);
    struct message_linked_list *next = working_free->next;
    free(working_free);
    working_free = next;
  }

And I would probably move this code to a separate function.