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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) 1992-2006 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 2,  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.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, USA.                                              --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNAT was originally developed  by the GNAT team at  New York University. --
  30 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 with Ada.Unchecked_Conversion;
  35
  36 with System.Storage_Elements;
  37 with System.Finalization_Root;
  38
  39 package System.Finalization_Implementation is
  40    pragma Elaborate_Body;
  41
  42    package SSE renames System.Storage_Elements;
  43    package SFR renames System.Finalization_Root;
  44
  45    ------------------------------------------------
  46    -- Finalization Management Abstract Interface --
  47    ------------------------------------------------
  48
  49    function To_Finalizable_Ptr is new Ada.Unchecked_Conversion
  50      (Source => System.Address, Target => SFR.Finalizable_Ptr);
  51
  52    Collection_Finalization_Started : constant SFR.Finalizable_Ptr :=
  53                                        To_Finalizable_Ptr (SSE.To_Address (1));
  54    --  This is used to implement the rule in RM-4.8(10.2/2) that requires an
  55    --  allocator to raise Program_Error if the collection finalization has
  56    --  already started. See also Ada.Finalization.List_Controller. Finalize on
  57    --  List_Controller first sets the list to Collection_Finalization_Started,
  58    --  to indicate that finalization has started. An allocator will call
  59    --  Attach_To_Final_List, which checks for the special value and raises
  60    --  Program_Error if appropriate. The value of
  61    --  Collection_Finalization_Started must be different from 'Access of any
  62    --  finalizable object, and different from null. See AI-280.
  63
  64    Global_Final_List : SFR.Finalizable_Ptr;
  65    --  This list stores the controlled objects defined in library-level
  66    --  packages. They will be finalized after the main program completion.
  67
  68    procedure Finalize_Global_List;
  69    --  The procedure to be called in order to finalize the global list;
  70
  71    procedure Attach_To_Final_List
  72      (L       : in out SFR.Finalizable_Ptr;
  73       Obj     : in out SFR.Finalizable;
  74       Nb_Link : Short_Short_Integer);
  75    --  Attach finalizable object Obj to the linked list L. Nb_Link controls
  76    --  the number of link of the linked_list, and can be either 0 for no
  77    --  attachement, 1 for simple linked lists or 2 for doubly linked lists
  78    --  or even 3 for a simple attachement of a whole array of elements.
  79    --  Attachement to a simply linked list is not protected against
  80    --  concurrent access and should only be used in contexts where it
  81    --  doesn't matter, such as for objects allocated on the stack. In the
  82    --  case of an attachment on a doubly linked list, L must not be null
  83    --  and Obj will be inserted AFTER the first element and the attachment
  84    --  is protected against concurrent call. Typically used to attach to
  85    --  a dynamically allocated object to a List_Controller (whose first
  86    --  element is always a dummy element)
  87
  88    procedure Finalize_List (L : SFR.Finalizable_Ptr);
  89    --  Call Finalize on each element of the list L;
  90
  91    procedure Finalize_One (Obj  : in out SFR.Finalizable);
  92    --  Call Finalize on Obj and remove its final list.
  93
  94    ---------------------
  95    -- Deep Procedures --
  96    ---------------------
  97
  98    procedure Deep_Tag_Initialize
  99      (L : in out SFR.Finalizable_Ptr;
 100       A : System.Address;
 101       B : Short_Short_Integer);
 102    --  Generic initialize for tagged objects with controlled components.
 103    --  A is the address of the object, L the finalization list when it needs
 104    --  to be attached and B the attachement level (see Attach_To_Final_List).
 105
 106    procedure Deep_Tag_Adjust
 107      (L : in out SFR.Finalizable_Ptr;
 108       A : System.Address;
 109       B : Short_Short_Integer);
 110    --  Generic adjust for tagged objects with controlled components.
 111    --  A is the address of the object, L the finalization list when it needs
 112    --  to be attached and B the attachement level (see Attach_To_Final_List).
 113
 114    procedure Deep_Tag_Finalize
 115      (L : in out SFR.Finalizable_Ptr;
 116       A : System.Address;
 117       B : Boolean);
 118    --  Generic finalize for tagged objects with controlled components.
 119    --  A is the address of the object, L the finalization list when it needs
 120    --  to be attached and B the attachement level (see Attach_To_Final_List).
 121
 122    procedure Deep_Tag_Attach
 123      (L : in out SFR.Finalizable_Ptr;
 124       A : System.Address;
 125       B : Short_Short_Integer);
 126    --  Generic attachement for tagged objects with controlled components.
 127    --  A is the address of the object, L the finalization list when it needs
 128    --  to be attached and B the attachement level (see Attach_To_Final_List).
 129
 130    -----------------------------
 131    -- Record Controller Types --
 132    -----------------------------
 133
 134    --  Definition of the types of the controller component that is included
 135    --  in records containing controlled components. This controller is
 136    --  attached to the finalization chain of the upper-level and carries
 137    --  the pointer of the finalization chain for the lower level.
 138
 139    type Limited_Record_Controller is new SFR.Root_Controlled with record
 140       F : SFR.Finalizable_Ptr;
 141    end record;
 142
 143    procedure Initialize (Object : in out Limited_Record_Controller);
 144    --  Does nothing.
 145
 146    procedure Finalize (Object : in out Limited_Record_Controller);
 147    --  Finalize the controlled components of the enclosing record by
 148    --  following the list starting at Object.F.
 149
 150    type Record_Controller is
 151       new Limited_Record_Controller with record
 152          My_Address : System.Address;
 153       end record;
 154
 155    procedure Initialize (Object : in out Record_Controller);
 156    --  Initialize the field My_Address to the Object'Address
 157
 158    procedure Adjust (Object : in out Record_Controller);
 159    --  Adjust the components and their finalization pointers by subtracting
 160    --  by the offset of the target and the source addresses of the assignment.
 161
 162    --  Inherit Finalize from Limited_Record_Controller
 163
 164    procedure Detach_From_Final_List (Obj : in out SFR.Finalizable);
 165    --  Remove the specified object from its Final list, which must be a
 166    --  doubly linked list.
 167
 168 end System.Finalization_Implementation;