From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00
	autolearn=unavailable autolearn_force=no version=3.4.4
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!.POSTED!not-for-mail
From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Strange crash on custom iterator
Date: Sat, 30 Jun 2018 15:25:36 +0100
Organization: A noiseless patient Spider
Message-ID: <lytvpks65b.fsf@pushface.org>
References: <70c11a71-3832-4f57-8127-f3f1c48a052f@googlegroups.com>
	<ly1scotsqq.fsf@pushface.org>
	<62e38ee4-f72f-4ed8-bef1-952040fb7f8d@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain
Injection-Info: reader02.eternal-september.org;
 posting-host="b23009edf2eaee529bf927e1c0a9ec62";
	logging-data="22039"; mail-complaints-to="abuse@eternal-september.org";
	posting-account="U2FsdGVkX19TsnwYerRwUR/LdbtoLhJ9JGEuwg3v4M8="
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.3 (darwin)
Cancel-Lock: sha1:sLXNNLNvrE/K8a7YINAD+3IFj2M=
	sha1:1C18rlL594Lfovr5VbAtYOYDmFA=
Xref: reader02.eternal-september.org comp.lang.ada:53475
Date: 2018-06-30T15:25:36+01:00
List-Id: <comp.lang.ada>

Lucretia <laguest9000@googlemail.com> writes:

> On Saturday, 30 June 2018 12:32:14 UTC+1, Simon Wright  wrote:
>> Lucretia <> writes:
>>
>> > I finally got around to getting back to my iterator and on a first
>> > test implementation, i.e. to just iterate over each element of the
>> > array, the thing crashes in the Element function when accessing the
>> > array through the cursor.
>> >
>> > The source is https://bpaste.net/show/6c5fca4c0ffd and the gdb session
>> > is https://bpaste.net/show/5b0cf9d2be79
>>
>> UCA.Encoding missing?
>
> Balls! https://bpaste.net/show/a0d108820ce6

First, I think Has_Element should probably be

   function Has_Element (Position : in Cursor) return Boolean is
   begin
      return Position.Index in Position.Data'Range;
   end Has_Element;

Second, there's something odd about the Address_To_Access_Conversions:
in Iterate, the address of the passed Container (which is on the
stack!!!)  appears in I.Data, but I.Data's length is 0.

I got it to work (at first glance) with

   type Cursor is
      record
         Data  : Unicode_String_Access := null;
         Index : Positive              := Positive'Last;
      end record;

   type Code_Point_Iterator is new Limited_Controlled and Code_Point_Iterators.Forward_Iterator with
      record
         Data  : Unicode_String_Access := null;
      end record;

and in Iterate

      return I : Code_Point_Iterator :=
         (Limited_Controlled with Data => new Unicode_String'(Container)) do

but of course you probably don't want the copy.