------------------------------------------------------------------------------
--                                                                          --
--                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
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--         S Y S T E M . T A S K I N G . T A S K _ A T T R I B U T E S      --
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--             Copyright (C) 1991-1994, Florida State University            --
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------------------------------------------------------------------------------

--  This package provides support for the body of Ada.Task_Attributes

with Ada.Finalization;

with System.Storage_Elements;

package System.Tasking.Task_Attributes is

   type Attribute is new Integer;
   --  A stand-in for the generic formal type of Ada.Task_Attributes
   --  in the following declarations.

   type Node;
   type Access_Node is access all Node;
   --  This needs comments ???

   function To_Access_Node is new Ada.Unchecked_Conversion
     (Access_Address, Access_Node);
   --  Used to fetch pointer to indirect attribute list. Declaration is in
   --  spec to avoid any problems with aliasing assumptions.

   type Dummy_Wrapper;
   type Access_Dummy_Wrapper is access all Dummy_Wrapper;
   pragma No_Strict_Aliasing (Access_Dummy_Wrapper);
   --  Needed to avoid possible incorrect aliasing situations from
   --  instantiation of Unchecked_Conversion in body of Ada.Task_Attributes.

   for Access_Dummy_Wrapper'Storage_Size use 0;
   --  Access_Dummy_Wrapper is a stand-in for the generic type Wrapper defined
   --  in Ada.Task_Attributes. The real objects allocated are always
   --  of type Wrapper, no Dummy_Wrapper objects are ever created.

   type Deallocator is access procedure (P : in out Access_Node);
   --  Called to deallocate an Wrapper. P is a pointer to a Node within

   type Instance;

   type Access_Instance is access all Instance;

   type Instance is new Ada.Finalization.Limited_Controlled with record
      Deallocate    : Deallocator;
      Initial_Value : aliased System.Storage_Elements.Integer_Address;

      Index : Direct_Index;
      --  The index of the TCB location used by this instantiation, if it is
      --  stored in the TCB, otherwise zero.

      Next : Access_Instance;
      --  Next instance in All_Attributes list
   end record;

   procedure Finalize (X : in out Instance);

   type Node is record
      Wrapper  : Access_Dummy_Wrapper;
      Instance : Access_Instance;
      Next     : Access_Node;
   end record;

   --  The following type is a stand-in for the actual wrapper type, which is
   --  different for each instantiation of Ada.Task_Attributes.

   type Dummy_Wrapper is record
      Dummy_Node : aliased Node;

      Value : aliased Attribute;
      --  The generic formal type, may be controlled
   end record;

   for Dummy_Wrapper'Alignment use Standard'Maximum_Alignment;
   --  A number of unchecked conversions involving Dummy_Wrapper_Access
   --  sources are performed in other units (e.g. Ada.Task_Attributes).
   --  Ensure that the designated object is always strictly enough aligned.

   In_Use : Direct_Index_Vector := 0;
   --  Set True for direct indexes that are already used (True??? type???)

   All_Attributes : Access_Instance;
   --  A linked list of all indirectly access attributes, which includes all
   --  those that require finalization.

   procedure Initialize_Attributes (T : Task_Id);
   --  Initialize all attributes created via Ada.Task_Attributes for T. This
   --  must be called by the creator of the task, inside Create_Task, via
   --  soft-link Initialize_Attributes_Link. On entry, abort must be deferred
   --  and the caller must hold no locks

   procedure Finalize_Attributes (T : Task_Id);
   --  Finalize all attributes created via Ada.Task_Attributes for T.
   --  This is to be called by the task after it is marked as terminated
   --  (and before it actually dies), inside Vulnerable_Free_Task, via the
   --  soft-link Finalize_Attributes_Link. On entry, abort must be deferred
   --  and T.L must be write-locked.

end System.Tasking.Task_Attributes;
