gcc/ada/sem_ch13.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                             S E M _ C H 1 3                              --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2005, 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 -- GNAT was originally developed  by the GNAT team at  New York University. --
  23 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  24 --                                                                          --
  25 ------------------------------------------------------------------------------
  26
  27 with Types; use Types;
  28 with Uintp; use Uintp;
  29
  30 package Sem_Ch13 is
  31    procedure Analyze_At_Clause                          (N : Node_Id);
  32    procedure Analyze_Attribute_Definition_Clause        (N : Node_Id);
  33    procedure Analyze_Enumeration_Representation_Clause  (N : Node_Id);
  34    procedure Analyze_Free_Statement                     (N : Node_Id);
  35    procedure Analyze_Record_Representation_Clause       (N : Node_Id);
  36    procedure Analyze_Code_Statement                     (N : Node_Id);
  37
  38    procedure Initialize;
  39    --  Initialize internal tables for new compilation
  40
  41    procedure Set_Enum_Esize (T : Entity_Id);
  42    --  This routine sets the Esize field for an enumeration type T, based
  43    --  on the current representation information available for T. Note that
  44    --  the setting of the RM_Size field is not affected. This routine also
  45    --  initializes the alignment field to zero.
  46
  47    function Minimum_Size
  48      (T      : Entity_Id;
  49       Biased : Boolean := False) return Nat;
  50    --  Given an elementary type, determines the minimum number of bits required
  51    --  to represent all values of the type. This function may not be called
  52    --  with any other types. If the flag Biased is set True, then the minimum
  53    --  size calculation that biased representation is used in the case of a
  54    --  discrete type, e.g. the range 7..8 gives a minimum size of 4 with
  55    --  Biased set to False, and 1 with Biased set to True. Note that the
  56    --  biased parameter only has an effect if the type is not biased, it
  57    --  causes Minimum_Size to indicate the minimum size of an object with
  58    --  the given type, of the size the type would have if it were biased. If
  59    --  the type is already biased, then Minimum_Size returns the biased size,
  60    --  regardless of the setting of Biased. Also, fixed-point types are never
  61    --  biased in the current implementation.
  62
  63    procedure Check_Constant_Address_Clause (Expr : Node_Id; U_Ent : Entity_Id);
  64    --  Expr is an expression for an address clause. This procedure checks
  65    --  that the expression is constant, in the limited sense that it is safe
  66    --  to evaluate it at the point the object U_Ent is declared, rather than
  67    --  at the point of the address clause. The condition for this to be true
  68    --  is that the expression has no variables, no constants declared after
  69    --  U_Ent, and no calls to non-pure functions. If this condition is not
  70    --  met, then an appropriate error message is posted. This check is applied
  71    --  at the point an object with an address clause is frozen, as well as for
  72    --  address clauses for tasks and entries.
  73
  74    procedure Check_Size
  75      (N      : Node_Id;
  76       T      : Entity_Id;
  77       Siz    : Uint;
  78       Biased : out Boolean);
  79    --  Called when size Siz is specified for subtype T. This subprogram checks
  80    --  that the size is appropriate, posting errors on node N as required.
  81    --  This check is effective for elementary types and bit-packed arrays.
  82    --  For other non-elementary types, a check is only made if an explicit
  83    --  size has been given for the type (and the specified size must match).
  84    --  The parameter Biased is set False if the size specified did not require
  85    --  the use of biased representation, and True if biased representation
  86    --  was required to meet the size requirement. Note that Biased is only
  87    --  set if the type is not currently biased, but biasing it is the only
  88    --  way to meet the requirement. If the type is currently biased, then
  89    --  this biased size is used in the initial check, and Biased is False.
  90    --  If the size is too small, and an error message is given, then both
  91    --  Esize and RM_Size are reset to the allowed minimum value in T.
  92
  93    function Rep_Item_Too_Early (T : Entity_Id; N : Node_Id) return Boolean;
  94    --  Called at the start of processing a representation clause or a
  95    --  representation pragma. Used to check that the representation item
  96    --  is not being applied to an incompleted type or to a generic formal
  97    --  type or a type derived from a generic formal type. Returns False if
  98    --  no such error occurs. If this error does occur, appropriate error
  99    --  messages are posted on node N, and True is returned.
 100
 101    function Rep_Item_Too_Late
 102      (T     : Entity_Id;
 103       N     : Node_Id;
 104       FOnly : Boolean := False) return Boolean;
 105    --  Called at the start of processing a representation clause or a
 106    --  representation pragma. Used to check that a representation item
 107    --  for entity T does not appear too late (according to the rules in
 108    --  RM 13.1(9) and RM 13.1(10)). N is the associated node, which in
 109    --  the pragma case is the pragma or representation clause itself, used
 110    --  for placing error messages if the item is too late.
 111    --
 112    --  Fonly is a flag that causes only the freezing rule (para 9) to be
 113    --  applied, and the tests of para 10 are skipped. This is appropriate
 114    --  for both subtype related attributes (Alignment and Size) and for
 115    --  stream attributes, which, although certainly not subtype related
 116    --  attributes, clearly should not be subject to the para 10 restrictions
 117    --  (see AI95-00137). Similarly, we also skip the para 10 restrictions for
 118    --  the Storage_Size case where they also clearly do not apply.
 119    --
 120    --  If the rep item is too late, an appropriate message is output and
 121    --  True is returned, which is a signal that the caller should abandon
 122    --  processing for the item. If the item is not too late, then False
 123    --  is returned, and the caller can continue processing the item.
 124    --
 125    --  If no error is detected, this call also as a side effect links the
 126    --  representation item onto the head of the representation item chain
 127    --  (referenced by the First_Rep_Item field of the entity).
 128    --
 129    --  Note: Rep_Item_Too_Late must be called with the underlying type in
 130    --  the case of a private or incomplete type. The protocol is to first
 131    --  check for Rep_Item_Too_Early using the initial entity, then take the
 132    --  underlying type, then call Rep_Item_Too_Late on the result.
 133
 134    function Same_Representation (Typ1, Typ2 : Entity_Id) return Boolean;
 135    --  Given two types, where the two types are related by possible derivation,
 136    --  determines if the two types have the same representation, or different
 137    --  representations, requiring the special processing for representation
 138    --  change. A False result is possible only for array, enumeration or
 139    --  record types.
 140
 141    procedure Validate_Unchecked_Conversion
 142      (N        : Node_Id;
 143       Act_Unit : Entity_Id);
 144    --  Validate a call to unchecked conversion. N is the node for the actual
 145    --  instantiation, which is used only for error messages. Act_Unit is the
 146    --  entity for the instantiation, from which the actual types etc for this
 147    --  instantiation can be determined. This procedure makes an entry in a
 148    --  table and/or generates an N_Validate_Unchecked_Conversion node. The
 149    --  actual checking is done in Validate_Unchecked_Conversions or in the
 150    --  back end as required.
 151
 152    procedure Validate_Unchecked_Conversions;
 153    --  This routine is called after calling the backend to validate
 154    --  unchecked conversions for size and alignment appropriateness.
 155    --  The reason it is called that late is to take advantage of any
 156    --  back-annotation of size and alignment performed by the backend.
 157
 158 end Sem_Ch13;