Re: Bug in Ada (SuSe 10.2) ?

[Vadim Godunko <vgodunko@gmail.com>]

On 22 фев, 22:21, Georg Bauhaus <rm.plus-bug.t...@maps.futureapps.de>
wrote:
> On Fri, 2008-02-22 at 08:10 -0800, billjones6...@yahoo.com wrote:
> > Of course, the danger is only eliminated when this language-defined
> > check is fully implemented in standard mode.
>
> Here is another dangling pointer. The program is
> giving me results varying with compiler/OS. I didn't see
> how accessiblity checks could help in this case, but
> then maybe this is a different issue?
>
> with Ada.Unchecked_Deallocation;
> with Ada.Text_IO;
>
> procedure News3 is
>    use Ada;
>
>    type Int_Ptr is access Integer;
>    Pointer: Int_Ptr;
>    Dangling_Pointer: Int_Ptr;
>
>    procedure Copy(Source: in out Int_Ptr; Target: out Int_Ptr) is
>       procedure Oops is new Unchecked_Deallocation
>         (Integer, Int_Ptr);
>    begin
>       Target := Source;
>       Oops(Source);
>    end Copy;
>
> begin
>    Pointer := new Integer'(42);
>    Copy(Pointer, Dangling_Pointer);
>
>    Text_IO.Put_Line(Integer'image(Dangling_Pointer.all));
> end News3;

Unchecked_Deallocation never makes program less erroneous. In the
example it is safe to remove instantiation of Unchecked_Deallocation.
Allocated memory will be automatically reclaimed after control flow
leave News3 subprogram, independent does or doesn't it is a main
subprogram.