Re: Gnat Problem - Freezing too soon

[russ lyttle <lyttlec@removegmail.com>]

On 3/1/19 8:08 PM, Anh Vo wrote:
> 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;
> 
Well, that worked. I may even come to understand why. Is this gnat only?