214 lines
10 KiB
Ada
214 lines
10 KiB
Ada
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------------------------------------------------------------------------------
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-- --
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-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
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-- --
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-- SYSTEM.TASKING.PROTECTED_OBJECTS.OPERATIONS --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 1992-2009, Free Software Foundation, Inc. --
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-- --
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-- GNARL is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNARL was developed by the GNARL team at Florida State University. --
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-- Extensive contributions were provided by Ada Core Technologies, Inc. --
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-- --
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------------------------------------------------------------------------------
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-- This package contains all the extended primitives related to protected
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-- objects with entries.
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-- The handling of protected objects with no entries is done in
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-- System.Tasking.Protected_Objects, the simple routines for protected
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-- objects with entries in System.Tasking.Protected_Objects.Entries. The
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-- split between Entries and Operations is needed to break circular
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-- dependencies inside the run time.
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-- Note: the compiler generates direct calls to this interface, via Rtsfind.
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-- Any changes to this interface may require corresponding compiler changes.
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with Ada.Exceptions;
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with System.Tasking.Protected_Objects.Entries;
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package System.Tasking.Protected_Objects.Operations is
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pragma Elaborate_Body;
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type Communication_Block is private;
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-- Objects of this type are passed between GNARL calls to allow RTS
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-- information to be preserved.
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procedure Protected_Entry_Call
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(Object : Entries.Protection_Entries_Access;
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E : Protected_Entry_Index;
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Uninterpreted_Data : System.Address;
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Mode : Call_Modes;
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Block : out Communication_Block);
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-- Make a protected entry call to the specified object.
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-- Pend a protected entry call on the protected object represented
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-- by Object. A pended call is not queued; it may be executed immediately
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-- or queued, depending on the state of the entry barrier.
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--
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-- E
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-- The index representing the entry to be called.
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--
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-- Uninterpreted_Data
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-- This will be returned by Next_Entry_Call when this call is serviced.
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-- It can be used by the compiler to pass information between the
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-- caller and the server, in particular entry parameters.
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--
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-- Mode
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-- The kind of call to be pended
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--
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-- Block
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-- Information passed between runtime calls by the compiler
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procedure Timed_Protected_Entry_Call
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(Object : Entries.Protection_Entries_Access;
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E : Protected_Entry_Index;
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Uninterpreted_Data : System.Address;
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Timeout : Duration;
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Mode : Delay_Modes;
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Entry_Call_Successful : out Boolean);
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-- Same as the Protected_Entry_Call but with time-out specified.
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-- This routines is used when we do not use ATC mechanism to implement
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-- timed entry calls.
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procedure Service_Entries (Object : Entries.Protection_Entries_Access);
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pragma Inline (Service_Entries);
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procedure PO_Service_Entries
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(Self_ID : Task_Id;
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Object : Entries.Protection_Entries_Access;
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Unlock_Object : Boolean := True);
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-- Service all entry queues of the specified object, executing the
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-- corresponding bodies of any queued entry calls that are waiting
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-- on True barriers. This is used when the state of a protected
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-- object may have changed, in particular after the execution of
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-- the statement sequence of a protected procedure.
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--
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-- Note that servicing an entry may change the value of one or more
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-- barriers, so this routine keeps checking barriers until all of
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-- them are closed.
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--
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-- This must be called with abort deferred and with the corresponding
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-- object locked.
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--
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-- If Unlock_Object is set True, then Object is unlocked on return,
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-- otherwise Object remains locked and the caller is responsible for
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-- the required unlock.
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procedure Complete_Entry_Body (Object : Entries.Protection_Entries_Access);
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-- Called from within an entry body procedure, indicates that the
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-- corresponding entry call has been serviced.
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procedure Exceptional_Complete_Entry_Body
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(Object : Entries.Protection_Entries_Access;
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Ex : Ada.Exceptions.Exception_Id);
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-- Perform all of the functions of Complete_Entry_Body. In addition,
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-- report in Ex the exception whose propagation terminated the entry
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-- body to the runtime system.
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procedure Cancel_Protected_Entry_Call (Block : in out Communication_Block);
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-- Attempt to cancel the most recent protected entry call. If the call is
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-- not queued abortably, wait until it is or until it has completed.
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-- If the call is actually cancelled, the called object will be
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-- locked on return from this call. Get_Cancelled (Block) can be
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-- used to determine if the cancellation took place; there
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-- may be entries needing service in this case.
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--
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-- Block passes information between this and other runtime calls.
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function Enqueued (Block : Communication_Block) return Boolean;
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-- Returns True if the Protected_Entry_Call which returned the
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-- specified Block object was queued; False otherwise.
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function Cancelled (Block : Communication_Block) return Boolean;
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-- Returns True if the Protected_Entry_Call which returned the
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-- specified Block object was cancelled, False otherwise.
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procedure Requeue_Protected_Entry
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(Object : Entries.Protection_Entries_Access;
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New_Object : Entries.Protection_Entries_Access;
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E : Protected_Entry_Index;
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With_Abort : Boolean);
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-- If Object = New_Object, queue the protected entry call on Object
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-- currently being serviced on the queue corresponding to the entry
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-- represented by E.
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--
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-- If Object /= New_Object, transfer the call to New_Object.E,
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-- executing or queuing it as appropriate.
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--
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-- With_Abort---True if the call is to be queued abortably, false
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-- otherwise.
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procedure Requeue_Task_To_Protected_Entry
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(New_Object : Entries.Protection_Entries_Access;
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E : Protected_Entry_Index;
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With_Abort : Boolean);
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-- Transfer task entry call currently being serviced to entry E
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-- on New_Object.
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--
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-- With_Abort---True if the call is to be queued abortably, false
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-- otherwise.
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function Protected_Count
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(Object : Entries.Protection_Entries'Class;
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E : Protected_Entry_Index)
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return Natural;
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-- Return the number of entry calls to E on Object
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function Protected_Entry_Caller
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(Object : Entries.Protection_Entries'Class) return Task_Id;
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-- Return value of E'Caller, where E is the protected entry currently
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-- being handled. This will only work if called from within an entry
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-- body, as required by the LRM (C.7.1(14)).
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-- For internal use only
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procedure PO_Do_Or_Queue
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(Self_ID : Task_Id;
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Object : Entries.Protection_Entries_Access;
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Entry_Call : Entry_Call_Link);
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-- This procedure either executes or queues an entry call, depending
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-- on the status of the corresponding barrier. It assumes that abort
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-- is deferred and that the specified object is locked.
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private
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type Communication_Block is record
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Self : Task_Id;
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Enqueued : Boolean := True;
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Cancelled : Boolean := False;
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end record;
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pragma Volatile (Communication_Block);
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-- When a program contains limited interfaces, the compiler generates the
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-- predefined primitives associated with dispatching selects. One of the
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-- parameters of these routines is of type Communication_Block. Even if
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-- the program lacks implementing concurrent types, the tasking runtime is
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-- dragged in unconditionally because of Communication_Block. To avoid this
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-- case, the compiler uses type Dummy_Communication_Block which defined in
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-- System.Soft_Links. If the structure of Communication_Block is changed,
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-- the corresponding dummy type must be changed as well.
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-- The Communication_Block seems to be a relic. At the moment, the
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-- compiler seems to be generating unnecessary conditional code based on
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-- this block. See the code generated for async. select with task entry
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-- call for another way of solving this ???
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end System.Tasking.Protected_Objects.Operations;
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