[pacman-dev] Problems with alpm_list_remove(_node)

[Aaron Griffin]

On Nov 9, 2007 3:20 PM, Dan McGee <dpmcgee at gmail.com> wrote:
> On Nov 9, 2007 2:55 PM, Xavier <shiningxc at gmail.com> wrote:
> > On Fri, Nov 09, 2007 at 08:54:52PM +0100, Nagy Gabor wrote:
> > > Some more issues:
> > > 1. You simply forgot about resetting the tail pointer when you remove
> > > the last element with alpm_list_remove.
> >
> > Yep, that's what explains the requiredby problem I noticed :
> > http://www.archlinux.org/pipermail/pacman-dev/2007-November/009919.html
> > Good catch :)
>
> This should fix it.
>
> diff --git a/lib/libalpm/alpm_list.c b/lib/libalpm/alpm_list.c
> index 6f6ee8f..f2e57c0 100644
> --- a/lib/libalpm/alpm_list.c
> +++ b/lib/libalpm/alpm_list.c
> @@ -311,6 +311,9 @@ alpm_list_t SYMEXPORT *alpm_list_remove(alpm_list_t *haystac
> k, const void *needl
>                                 /* Normal case, non-head node */
>                                 if(i->next) {
>                                         i->next->prev = i->prev;
> +                               } else {
> +                                       /* We are on the tail node, need to upda
> te the back ref */
> +                                       haystack->prev = i->prev;
>                                 }
>                                 if(i->prev) {
>                                         i->prev->next = i->next;

Be careful here - the special cases or head nodes typically needed to
be added after the "if next" and "if prev" stuff already there, as
they never took the terminal nodes to be any different. By that, I
mean

   if(next) { do stuff }
   if(prev) { do stuff }
   if(!next) { tail node }

I'm sure it could be restructured, but I'll leave that for the CS students 8)