From: Adam Beneschan <adam@irvine.com>
Subject: Re: Allocators and exceptions
Date: Tue, 11 Sep 2007 14:56:54 -0700
Date: 2007-09-11T14:56:54-07:00 [thread overview]
Message-ID: <1189547814.740732.220140@x40g2000prg.googlegroups.com> (raw)
In-Reply-To: <1189524788.300591.312380@w3g2000hsg.googlegroups.com>
On Sep 11, 8:33 am, I wrote:
> On Sep 10, 7:36 pm, "Randy Brukardt" <ra...@rrsoftware.com> wrote:
>
> > (2) I believe that the current wording of the standard *requires* that
> > reclamation *not* be performed in examples like this, at least if there are
> > any controlled components in the type. That's because there is no permission
> > in Ada to do finalization early - it has to be done only if the object is
> > explicitly destroyed or when the master goes out of scope -- which for an
> > allocated object is when the *type* goes out of scope.
>
> It sure seemed to me that one could create an example in which, due to
> a default initialization on a component that contains a function call
> that does some interesting stuff, the automatic reclamation Maciej is
> asking for would lead to a dangling reference or something just as
> bad.
OK, I think I have one. GNAT compiles and runs it, although I haven't
checked the language rules carefully to make sure it's legal.
----------------------------------------------------------------------------
package Pak1 is
type Rec1 is limited private;
type Rec1_Acc is access all Rec1;
function Func1 (R : Rec1_Acc) return Integer;
private
type Rec1 is limited record
F1 : Integer := 123;
F2 : Integer := Func1 (Rec1'Unchecked_Access);
end record;
end Pak1;
package body Pak1 is
P : Rec1_Acc;
function Func1 (R : Rec1_Acc) return Integer is
begin
P := R;
if R.F1 > 100 then
raise Constraint_Error;
end if;
return 1;
end Func1;
end Pak1;
with Pak1;
procedure test84 is
X : Pak1.Rec1_Acc := new Pak1.Rec1;
begin
null;
end test84;
----------------------------------------------------------------------------
When the allocator "new Pak1.Rec1" is evaluated, an object of type
Rec1 is created; then F1 is set to 123; then the code attempts to
initialize F2 by calling Func1. The parameter is the
'Unchecked_Access of the object that has already been created. Func1
saves this in the global P. Then it raises Constraint_Error. If the
Constraint_Error caused the object of type Rec1 to be deallocated and
thus no longer exist, P would then be left as a dangling reference.
-- Adam
next prev parent reply other threads:[~2007-09-11 21:56 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-09 7:40 Allocators and exceptions Maciej Sobczak
2007-09-09 12:17 ` anon
2007-09-09 20:31 ` Maciej Sobczak
2007-09-09 22:43 ` Simon Wright
2007-09-10 12:10 ` Maciej Sobczak
2007-09-10 19:08 ` Simon Wright
2007-09-10 2:56 ` anon
2007-09-10 12:42 ` Dmitry A. Kazakov
2007-09-10 21:48 ` Maciej Sobczak
2007-09-11 9:16 ` Dmitry A. Kazakov
2007-09-11 9:19 ` Maciej Sobczak
2007-09-11 12:27 ` Dmitry A. Kazakov
2007-09-11 19:07 ` Maciej Sobczak
2007-09-11 22:56 ` Georg Bauhaus
2007-09-12 12:36 ` Maciej Sobczak
2007-09-12 22:19 ` Randy Brukardt
2007-09-12 9:32 ` Dmitry A. Kazakov
2007-09-12 12:42 ` Maciej Sobczak
2007-09-12 15:25 ` Dmitry A. Kazakov
2007-09-12 12:29 ` Stephen Leake
2007-09-12 12:46 ` Maciej Sobczak
2007-09-12 20:53 ` Simon Wright
2007-09-12 22:32 ` Randy Brukardt
2007-09-12 23:43 ` Simon Wright
2007-09-13 3:42 ` Randy Brukardt
2007-09-13 3:36 ` Randy Brukardt
2007-09-13 9:43 ` Maciej Sobczak
2007-09-12 22:25 ` Randy Brukardt
2007-09-13 11:51 ` Stephen Leake
2007-09-12 14:14 ` Markus E L
2007-09-10 10:37 ` Allocators and exceptions => Read Me First anon
2007-09-10 12:16 ` Maciej Sobczak
2007-09-10 22:10 ` Allocators and exceptions => Trying Again anon
2007-09-10 23:15 ` Markus E L
2007-09-10 15:44 ` Allocators and exceptions Adam Beneschan
2007-09-10 21:58 ` Maciej Sobczak
2007-09-10 22:07 ` Jeffrey R. Carter
2007-09-11 9:14 ` Dmitry A. Kazakov
2007-09-11 9:23 ` Maciej Sobczak
2007-09-11 2:36 ` Randy Brukardt
2007-09-11 15:33 ` Adam Beneschan
2007-09-11 19:21 ` Maciej Sobczak
2007-09-11 21:56 ` Adam Beneschan [this message]
2007-09-12 0:34 ` Jeffrey R. Carter
2007-09-12 12:13 ` Maciej Sobczak
2007-09-12 16:34 ` Jeffrey R. Carter
2007-09-12 23:50 ` Jeffrey R. Carter
2007-09-12 12:22 ` Maciej Sobczak
2007-09-12 14:11 ` Markus E L
2007-09-12 16:08 ` Adam Beneschan
2007-09-12 20:35 ` Dmitry A. Kazakov
2007-09-12 21:01 ` Adam Beneschan
2007-09-12 22:45 ` Randy Brukardt
2007-09-13 7:48 ` Dmitry A. Kazakov
2007-09-12 3:08 ` Allocators and exceptions -- Debugging says memory leak! anon
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