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Newsgroups: comp.lang.ada
Subject: Re: GCC 4.0 Ada.Containers Cursor danger.
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From: Matthew Heaney <matthewjheaney@earthlink.net>
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Date: Sat, 16 Jul 2005 23:24:26 GMT
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"Dmitriy Anisimkov" <anisimkov@yahoo.com> writes:

> IMHO the cursors in the Ada.Containers implemented in GCC 4.0
> dangerouse like pointers in C/C++.
> 
> Look at the code below.

Here is a simplified version of your example:

with Ada.Containers.Indefinite_Hashed_Maps;  use Ada.Containers;
with Ada.Strings.Hash;                       use Ada.Strings;

procedure Test_HM is
   package Map_Types is
      new Indefinite_Hashed_Maps (String, Integer, Hash, "=");
   use Map_Types;

   M     : Map;
   C, C2 : Cursor;
   B     : Boolean;

begin

   M.Insert ("one", 1);

   M.Insert ("two", 2, C, B);
   pragma Assert (B);

   M.Insert ("three", 3);

   pragma Assert (Has_Element (C));
   pragma Assert (Key (C) = "two");
   pragma Assert (Element (C) = 2);

   C2 := M.Find ("two");
   pragma Assert (Has_Element (C2));
   pragma Assert (Key (C) = "two");
   pragma Assert (Element (C) = 2);

   M.Delete (C2);
   pragma Assert (not Has_Element (C2));
   pragma Assert (not M.Contains ("two"));

   Replace_Element (C, -2);  -- dangling cursor

end Test_HM;


When I compile it as follows (on WinXP):

gnatmake -gnata -g -gnat05 test_hm

and then run it, I get this output:

raised SYSTEM.ASSERTIONS.ASSERT_FAILURE : bad cursor in Replace_Element


Does this behavior adequately satisfy your needs?