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=-0.3 required=5.0 tests=BAYES_00,
	REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4
X-Google-Thread: 103376,d0c649cbc04d397b
X-Google-Attributes: gid103376,public
X-Google-Language: ENGLISH,ASCII
Path: 
 g2news2.google.com!news4.google.com!news2.volia.net!newsfeed01.sul.t-online.de!t-online.de!news.belwue.de!newsfeed.arcor.de!newsspool2.arcor-online.net!news.arcor.de.POSTED!not-for-mail
From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Weird problem with recursion and tasks
Newsgroups: comp.lang.ada
User-Agent: 40tude_Dialog/2.0.15.1
MIME-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: 8bit
Reply-To: mailbox@dmitry-kazakov.de
Organization: cbb software GmbH
References: <1165116074.751484.99560@j44g2000cwa.googlegroups.com>
Date: Sun, 3 Dec 2006 10:43:33 +0100
Message-ID: <almtzna7896n.1r4xuyjpsu3hn.dlg@40tude.net>
NNTP-Posting-Date: 03 Dec 2006 10:43:33 CET
NNTP-Posting-Host: 6b280874.newsspool2.arcor-online.net
X-Trace: 
 DXC=G6PFA04d\MIAa;:RKVJ>LEA9EHlD;3YcB4Fo<]lROoRAFl8W>\BH3YBk\:0L\G_VLJDNcfSJ;bb[EIRnRBaCd<MNA;Wf5UIeD0C?Ug]e89R4WF
X-Complaints-To: usenet-abuse@arcor.de
Xref: g2news2.google.com comp.lang.ada:7793
Date: 2006-12-03T10:43:33+01:00
List-Id: <comp.lang.ada>

On 2 Dec 2006 19:21:14 -0800, christopher.orihuela@gmail.com wrote:

> I was implementing a concurrent version of QuickSort (each half in a
> different task) when I realized that sometimes the recursive task
> didn't execute.
> �Could anybody tell me why for values of MaxI > 4 I allways get a
> higer count of A in the following program? Thanks.

It looks like a compiler bug to me (GNAT 3.15p, Windows). If we added a few
put_lines:

With Ada.Text_IO, Ada.Strings.Fixed;
Use  Ada.Text_IO, Ada.Strings.Fixed;

Procedure My_Proc is

   protected type Counter is
      Procedure IncA;
      Procedure IncB;
      Procedure ShowCounts;
   private
      A, B: Natural := 0;
   end Counter;

   protected body Counter is
      Procedure IncA is
      begin
         A := A+1;
      end IncA;
      Procedure IncB is
      begin
         B := B+1;
      end IncB;
      Procedure ShowCounts is
      begin
         Put_Line("A: " & Integer'Image(A));
         Put_Line("B: " & Integer'Image(B));
      end ShowCounts;
   end Counter;

   MyCounter : Counter;

   Procedure Recursive (I : Natural; MaxI : Natural) is
   begin

      if (I >= MaxI) then
           return;
      end if;

      MyCounter.IncA;
      MyCounter.IncA;

      declare
         task My_Recursive_Task;
         task body My_Recursive_Task is
         begin
            Put_Line(I * " " & "Start task");
            Recursive(I+1, MaxI);
            MyCounter.IncB;
            Put_Line(I * " " & "Stop task");
         end My_Recursive_Task;

      begin
         Recursive(I+1, MaxI);
         MyCounter.IncB;
      end;

   end Recursive;
   
begin
   Recursive (1, 5);
   MyCounter.ShowCounts;
end My_Proc;

we would see that starting with MaxI=4 and higher some of My_Recursive_Task
are not awaited for termination by their masters, when the task object gets
out of scope. I see it in breach with ARM 7.6.1(4).

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de