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   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --    S Y S T E M . F I N A L I Z A T I O N _ I M P L E M E N T A T I O N   --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2009, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 with Ada.Unchecked_Conversion;
  33
  34 with System.Storage_Elements;
  35 with System.Finalization_Root;
  36
  37 package System.Finalization_Implementation is
  38    pragma Elaborate_Body;
  39
  40    package SSE renames System.Storage_Elements;
  41    package SFR renames System.Finalization_Root;
  42
  43    ------------------------------------------------
  44    -- Finalization Management Abstract Interface --
  45    ------------------------------------------------
  46
  47    function To_Finalizable_Ptr is new Ada.Unchecked_Conversion
  48      (Source => System.Address, Target => SFR.Finalizable_Ptr);
  49
  50    Collection_Finalization_Started : constant SFR.Finalizable_Ptr :=
  51                                        To_Finalizable_Ptr (SSE.To_Address (1));
  52    --  This is used to implement the rule in RM 4.8(10.2/2) that requires an
  53    --  allocator to raise Program_Error if the collection finalization has
  54    --  already started. See also Ada.Finalization.List_Controller. Finalize on
  55    --  List_Controller first sets the list to Collection_Finalization_Started,
  56    --  to indicate that finalization has started. An allocator will call
  57    --  Attach_To_Final_List, which checks for the special value and raises
  58    --  Program_Error if appropriate. The Collection_Finalization_Started value
  59    --  must be different from 'Access of any finalizable object, and different
  60    --  from null. See AI-280.
  61
  62    Global_Final_List : SFR.Finalizable_Ptr;
  63    --  This list stores the controlled objects defined in library-level
  64    --  packages. They will be finalized after the main program completion.
  65
  66    procedure Finalize_Global_List;
  67    --  The procedure to be called in order to finalize the global list
  68
  69    procedure Attach_To_Final_List
  70      (L       : in out SFR.Finalizable_Ptr;
  71       Obj     : in out SFR.Finalizable;
  72       Nb_Link : Short_Short_Integer);
  73    --  Attach finalizable object Obj to the linked list L. Nb_Link controls the
  74    --  number of link of the linked_list, and is one of: 0 for no attachment, 1
  75    --  for simple linked lists or 2 for doubly linked lists or even 3 for a
  76    --  simple attachment of a whole array of elements. Attachment to a simply
  77    --  linked list is not protected against concurrent access and should only
  78    --  be used in contexts where it doesn't matter, such as for objects
  79    --  allocated on the stack. In the case of an attachment on a doubly linked
  80    --  list, L must not be null and Obj will be inserted AFTER the first
  81    --  element and the attachment is protected against concurrent call.
  82    --  Typically used to attach to a dynamically allocated object to a
  83    --  List_Controller (whose first element is always a dummy element)
  84
  85    type Finalizable_Ptr_Ptr is access all SFR.Finalizable_Ptr;
  86    --  A pointer to a finalization list. This is used as the type of the extra
  87    --  implicit formal which are passed to build-in-place functions that return
  88    --  controlled types (see Sem_Ch6). That extra formal is then passed on to
  89    --  Move_Final_List (below).
  90
  91    procedure Move_Final_List
  92      (From : in out SFR.Finalizable_Ptr;
  93       To   : Finalizable_Ptr_Ptr);
  94    --  Move all objects on From list to To list. This is used to implement
  95    --  build-in-place function returns. The return object is initially placed
  96    --  on a finalization list local to the return statement, in case the
  97    --  return statement is left prematurely (due to raising an exception,
  98    --  being aborted, or a goto or exit statement). Once the return statement
  99    --  has completed successfully, Move_Final_List is called to move the
 100    --  return object to the caller's finalization list.
 101
 102    procedure Finalize_List (L : SFR.Finalizable_Ptr);
 103    --  Call Finalize on each element of the list L
 104
 105    procedure Finalize_One (Obj  : in out SFR.Finalizable);
 106    --  Call Finalize on Obj and remove its final list
 107
 108    ---------------------
 109    -- Deep Procedures --
 110    ---------------------
 111
 112    procedure Deep_Tag_Attach
 113      (L : in out SFR.Finalizable_Ptr;
 114       A : System.Address;
 115       B : Short_Short_Integer);
 116    --  Generic attachment for tagged objects with controlled components.
 117    --  A is the address of the object, L the finalization list when it needs
 118    --  to be attached and B the attachment level (see Attach_To_Final_List).
 119
 120    -----------------------------
 121    -- Record Controller Types --
 122    -----------------------------
 123
 124    --  Definition of the types of the controller component that is included
 125    --  in records containing controlled components. This controller is
 126    --  attached to the finalization chain of the upper-level and carries
 127    --  the pointer of the finalization chain for the lower level.
 128
 129    type Limited_Record_Controller is new SFR.Root_Controlled with record
 130       F : SFR.Finalizable_Ptr;
 131    end record;
 132
 133    overriding procedure Initialize (Object : in out Limited_Record_Controller);
 134    --  Does nothing currently
 135
 136    overriding procedure Finalize (Object : in out Limited_Record_Controller);
 137    --  Finalize the controlled components of the enclosing record by following
 138    --  the list starting at Object.F.
 139
 140    type Record_Controller is
 141       new Limited_Record_Controller with record
 142          My_Address : System.Address;
 143       end record;
 144
 145    overriding procedure Initialize (Object : in out Record_Controller);
 146    --  Initialize the field My_Address to the Object'Address
 147
 148    overriding procedure Adjust (Object : in out Record_Controller);
 149    --  Adjust the components and their finalization pointers by subtracting by
 150    --  the offset of the target and the source addresses of the assignment.
 151
 152    --  Inherit Finalize from Limited_Record_Controller
 153
 154    procedure Detach_From_Final_List (Obj : in out SFR.Finalizable);
 155    --  Remove the specified object from its Final list, which must be a doubly
 156    --  linked list.
 157
 158 end System.Finalization_Implementation;