gcc/ada/exp_tss.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                              E X P _ T S S                               --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --                                                                          --
  10 --          Copyright (C) 1992-2001 Free Software Foundation, Inc.          --
  11 --                                                                          --
  12 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  13 -- terms of the  GNU General Public License as published  by the Free Soft- --
  14 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  15 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  16 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  17 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  18 -- for  more details.  You should have  received  a copy of the GNU General --
  19 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  20 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  21 -- MA 02111-1307, USA.                                                      --
  22 --                                                                          --
  23 -- GNAT was originally developed  by the GNAT team at  New York University. --
  24 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
  25 --                                                                          --
  26 ------------------------------------------------------------------------------
  27
  28 --  Type Support Subprogram (TSS) handling
  29
  30 with Types; use Types;
  31
  32 package Exp_Tss is
  33
  34    --  A type support subprogram (TSS) is an internally generated function or
  35    --  procedure that is associated with a particular type. Examples are the
  36    --  implicit initialization procedure, and subprograms for the Input and
  37    --  Output attributes.
  38
  39    --  A given TSS is either generated once at the point of the declaration of
  40    --  the type, or it is generated as needed in clients, but only one copy is
  41    --  required in any one generated object file. The choice between these two
  42    --  possibilities is made on a TSS-by-TSS basis depending on the estimation
  43    --  of how likely the TSS is to be used. Initialization procedures fall in
  44    --  the first category, for example, since it is likely that any declared
  45    --  type will be used in a context requiring initialization, but the stream
  46    --  attributes use the second approach, since it is more likely that they
  47    --  will not be used at all, or will only be used in one client in any case.
  48
  49    --  A TSS is identified by its Chars name, i.e. for a given TSS type, the
  50    --  same name is used for all types, e.g. the initialization routine has
  51    --  the name _init for all types.
  52
  53    --  The TSS's for a given type are stored in an element list associated with
  54    --  the type, and referenced from the TSS_Elist field of the N_Freeze_Entity
  55    --  node associated with the type (all types that need TSS's always need to
  56    --  be explicitly frozen, so the N_Freeze_Entity node always exists).
  57
  58    function TSS (Typ : Entity_Id; Nam : Name_Id) return Entity_Id;
  59    --  Finds the TSS with the given name associated with the given type. If
  60    --  no such TSS exists, then Empty is returned.
  61
  62    procedure Set_TSS (Typ : Entity_Id; TSS : Entity_Id);
  63    --  This procedure is used to install a newly created TSS. The second
  64    --  argument is the entity for such a new TSS. This entity is placed in
  65    --  the TSS list for the type given as the first argument, replacing an
  66    --  old entry of the same name if one was present. The tree for the body
  67    --  of this TSS, which is not analyzed yet, is placed in the actions field
  68    --  of the freeze node for the type. All such bodies are inserted into the
  69    --  main tree and analyzed at the point at which the freeze node itself is
  70    --  is expanded.
  71
  72    procedure Copy_TSS (TSS : Entity_Id; Typ : Entity_Id);
  73    --  Given an existing TSS for another type (which is already installed,
  74    --  analyzed and expanded), install it as the corresponding TSS for Typ.
  75    --  Note that this just copies a reference, not the tree. This can also
  76    --  be used to initially install a TSS in the case where the subprogram
  77    --  for the TSS has already been created and its declaration processed.
  78
  79    function Init_Proc (Typ : Entity_Id) return Entity_Id;
  80    pragma Inline (Init_Proc);
  81    --  Obtains the _init TSS entry for the given type. This function call is
  82    --  equivalent to TSS (Typ, Name_uInit). The _init TSS is the procedure
  83    --  used to initialize otherwise uninitialized instances of a type. If
  84    --  there is no _init TSS, then the type requires no initialization. Note
  85    --  that subtypes and implicit types never have an _init TSS since subtype
  86    --  objects are always initialized using the initialization procedure for
  87    --  the corresponding base type (see Base_Init_Proc function). A special
  88    --  case arises for concurrent types. Such types do not themselves have an
  89    --  _init TSR, but initialization is required. The initialization procedure
  90    --  used is the one fot the corresponding record type (see Base_Init_Proc).
  91
  92    function Base_Init_Proc (Typ : Entity_Id) return Entity_Id;
  93    --  Obtains the _Init TSS entry from the base type of the entity, and also
  94    --  deals with going indirect through the Corresponding_Record_Type field
  95    --  for concurrent objects (which are initialized with the initialization
  96    --  routine for the corresponding record type). Returns Empty if there is
  97    --  no _Init TSS entry for the base type.
  98
  99    procedure Set_Init_Proc (Typ : Entity_Id; Init : Entity_Id);
 100    pragma Inline (Set_Init_Proc);
 101    --  The second argument is the _init TSS to be established for the type
 102    --  given as the first argument. Equivalent to Set_TSS (Typ, Init).
 103
 104    function Has_Non_Null_Base_Init_Proc (Typ : Entity_Id) return Boolean;
 105    --  Returns true if the given type has a defined Base_Init_Proc and
 106    --  this init proc is not a null init proc (null init procs occur as
 107    --  a result of the processing for Initialize_Scalars. This function
 108    --  is used to test for the presence of an Init_Proc in cases where
 109    --  a null init proc is considered equivalent to no Init_Proc.
 110
 111 end Exp_Tss;