Re: Generic Embedded List Nodes

[Warren <ve3wwg@gmail.com>]

On Friday, 1 July 2016 09:49:19 UTC-4, Warren  wrote:
> On Saturday, 25 June 2016 01:50:41 UTC-4, Niklas Holsti  wrote:
> > On 16-06-24 15:49 , Warren wrote:
> ..
> >     procedure Insert_At_Head (
> >        List : access List_T;
> >        Node : in     Emb_Node_Ref_T)
> >     is
> >     begin
> >        if List.Next /= null then
> >           List.Next.Prev := Node;
> >        end if;
> >        Node.Next := List.Next;
> >        List.Next := Node;
> >        Node.Prev := Emb_Node_Ref_T (List);
> >     end Insert_At_Head;
> 
> Niklas: I finally got a few minutes to revisit this and worked up a full example based upon yours.  I fear that the design is still flawed. I'm using a slightly modified version of this, but basically, the problem occurs at the line:
> 
> >        Node.Prev := Emb_Node_Ref_T (List);
> 
> with the exception:
> 
> raised PROGRAM_ERROR : niklas.adb:14 accessibility check failed
> 
> My example code is located on github here:  https://github.com/ve3wwg/ada_embedded_list
> 
> Maybe there is pilot error somewhere. I'm using: GNATMAKE 6.1.0.
> 
> Warren

Sorry, nevermind. When I allocate the list with:

    List1:   aliased access List_T := new List_T;

it is fine.  I suppose that the runtime was worried about dangling pointers when it was originally allocated on the stack frame in:

    List1:   aliased List_T;

Warren