Re: Gnat Problem - Freezing too soon

[Anh Vo <anhvofrcaus@gmail.com>]

On Friday, March 1, 2019 at 1:50:12 PM UTC-8, russ lyttle wrote:
> On 3/1/19 11:54 AM, Anh Vo wrote:
> > On Friday, March 1, 2019 at 6:21:26 AM UTC-8, russ lyttle wrote:
> >> On 2/28/19 7:49 PM, Anh Vo wrote:
> >>> On Thursday, February 28, 2019 at 2:11:11 PM UTC-8, russ lyttle wrote:
> >>>> On 2/28/19 4:22 PM, Simon Wright wrote:
> >>>>> russ lyttle <lyttlec@removegmail.com> writes:
> >>>>>
> >>>>>> Example from the bookAnalysable Real-Time Systems :
> >>>>>>
> >>> ---------
> >>>>
> >>>> Would I be submitting a bug report against an already patched version of
> >>>> gnat?
> >>>
> >>> Again, please post sporadics.ads in its entirety. So, we can duplicate your finding or not.
> >>>    
> >>>
> >> Thanks for responding. We found it definitely a bug in gnat and are
> >> submitting a bug report.
> > 
> > It is fine to send in a report if you are confident that it is a bug in latest GNAT. Otherwise, we would like to see the content of sporadics.ads. So, we can either confirm or not your finding.
> >   
> > 
> Here they are. These are from Analysable Real-Time Systems Progrmmed in 
> Ada, Chap.20, Pg. 472-473. Line 29 gives different error from line 44.
> 
> Full code for sporadics.ads:
> 
> with System; use System;
> with Ada.Real_Time; use Ada.Real_Time;
> package Sporadics is
> 
>     type Sporadic_Invoke_Interface is Synchronized Interface;
>     procedure Start (S: in out Sporadic_Invoke_Interface)
>        is abstract;
>     type Any_Sporadic_Invoke_Interface is access all
>       Sporadic_Invoke_Interface'Class;
> 
>     type Sporadic_Thread_Interface is Synchronized Interface;
>     procedure Wait_Start (S: in out Sporadic_Thread_Interface)
>        is abstract;
>     type Any_Sporadic_Thread_Interface is access all
>       Sporadic_Thread_Interface'Class;
> 
>     type Sporadic_State is abstract tagged
>        record
> 	 Pri : Priority;
> 	 Ceiling_Priority : Priority;
> 	 MIT_In_Mili : Time_Span;
>        end record;
>     procedure Initialize_Code (S: in out Sporadic_State)
>        is abstract;
>     procedure Sporadic_Code (S: in out Sporadic_State)
>        is abstract;
>     type Any_Sporadic_State is access all Sporadic_State'Class;
> 
>     protected type Sporadic_Agent (S: Any_Sporadic_State)
>       --with Priority => S.Ceiling_Prioriy
>     is
>        new Sporadic_Invoke_Interface and
>            Sporadic_Thread_Interface
>       with
>       -- for the Start operation
>       overriding procedure Start;
>       overriding entry Wait_Start;
>     private
>        Start_Open : Boolean := False;
>     end Sporadic_Agent;
> 
>     task type Sporadic (S : Any_Sporadic_State;
> 		       A : Any_Sporadic_Thread_Interface)
>       with Priority => S.pri
>         is
> 
>     end Sporadic;
> end Sporadics;
> -----------------------------------------------------------------------
> Full code for sporadics.adb:
> package body Sporadics is
>     protected body Sporadic_Agent is
>        procedure Start is
>        begin
> 	 Start_Open := False;
>        end Start;
> 
>        entry Wait_Start
>        when Start_Open is
>        begin
> 	 Start_Open := False;
>        end Wait_Start;
>     end Sporadic_Agent;
> 
>        task body Sporadic is
>        begin
> 	 S.Initialize_Code;
> 	 loop
> 	    A.Wait_Start;
> 	    S.Sporadic_Code;
> 	 end loop;
>        end Sporadic;
>     end Sporadics;

This problem also occurred with GNAT Community 2018 on Windows.

While waiting for fixes in GNAT Community 2019, the work around is changing the definition of type Any_Sporadic_State as shown below.

    type Any_Sporadic_State is not null access all Sporadic_State'Class;