gcc/ada/exp_ch13.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                             E X P _ C H 1 3                              --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2004, 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,  59 Temple Place - Suite 330,  Boston, --
  20 -- MA 02111-1307, 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 Atree;    use Atree;
  28 with Checks;   use Checks;
  29 with Einfo;    use Einfo;
  30 with Exp_Ch3;  use Exp_Ch3;
  31 with Exp_Ch6;  use Exp_Ch6;
  32 with Exp_Imgv; use Exp_Imgv;
  33 with Exp_Tss;  use Exp_Tss;
  34 with Exp_Util; use Exp_Util;
  35 with Nlists;   use Nlists;
  36 with Nmake;    use Nmake;
  37 with Rtsfind;  use Rtsfind;
  38 with Sem;      use Sem;
  39 with Sem_Ch7;  use Sem_Ch7;
  40 with Sem_Ch8;  use Sem_Ch8;
  41 with Sem_Eval; use Sem_Eval;
  42 with Sem_Util; use Sem_Util;
  43 with Sinfo;    use Sinfo;
  44 with Snames;   use Snames;
  45 with Stand;    use Stand;
  46 with Stringt;  use Stringt;
  47 with Tbuild;   use Tbuild;
  48 with Uintp;    use Uintp;
  49
  50 package body Exp_Ch13 is
  51
  52    procedure Expand_External_Tag_Definition (N : Node_Id);
  53    --  The code to assign and register an external tag must be elaborated
  54    --  after the dispatch table has been created, so the expansion of the
  55    --  attribute definition node is delayed until after the type is frozen.
  56
  57    ------------------------------------------
  58    -- Expand_N_Attribute_Definition_Clause --
  59    ------------------------------------------
  60
  61    --  Expansion action depends on attribute involved
  62
  63    procedure Expand_N_Attribute_Definition_Clause (N : Node_Id) is
  64       Loc : constant Source_Ptr := Sloc (N);
  65       Exp : constant Node_Id    := Expression (N);
  66       Ent : Entity_Id;
  67       V   : Node_Id;
  68
  69    begin
  70       Ent := Entity (Name (N));
  71
  72       if Is_Type (Ent) then
  73          Ent := Underlying_Type (Ent);
  74       end if;
  75
  76       case Get_Attribute_Id (Chars (N)) is
  77
  78          -------------
  79          -- Address --
  80          -------------
  81
  82          when Attribute_Address =>
  83
  84             --  If there is an initialization which did not come from
  85             --  the source program, then it is an artifact of our
  86             --  expansion, and we suppress it. The case we are most
  87             --  concerned about here is the initialization of a packed
  88             --  array to all false, which seems inappropriate for a
  89             --  variable to which an address clause is applied. The
  90             --  expression may itself have been rewritten if the type is a
  91             --  packed array, so we need to examine whether the original
  92             --  node is in the source.
  93
  94             declare
  95                Decl : constant Node_Id := Declaration_Node (Ent);
  96             begin
  97                if Nkind (Decl) = N_Object_Declaration
  98                   and then Present (Expression (Decl))
  99                   and then
 100                    not Comes_From_Source (Original_Node (Expression (Decl)))
 101                then
 102                   Set_Expression (Decl, Empty);
 103                end if;
 104             end;
 105
 106          ---------------
 107          -- Alignment --
 108          ---------------
 109
 110          when Attribute_Alignment =>
 111
 112             --  As required by Gigi, we guarantee that the operand is an
 113             --  integer literal (this simplifies things in Gigi).
 114
 115             if Nkind (Exp) /= N_Integer_Literal then
 116                Rewrite
 117                  (Exp, Make_Integer_Literal (Loc, Expr_Value (Exp)));
 118             end if;
 119
 120          ------------------
 121          -- Storage_Size --
 122          ------------------
 123
 124          when Attribute_Storage_Size =>
 125
 126             --  If the type is a task type, then assign the value of the
 127             --  storage size to the Size variable associated with the task.
 128             --    task_typeZ := expression
 129
 130             if Ekind (Ent) = E_Task_Type then
 131                Insert_Action (N,
 132                  Make_Assignment_Statement (Loc,
 133                    Name => New_Reference_To (Storage_Size_Variable (Ent), Loc),
 134                    Expression =>
 135                      Convert_To (RTE (RE_Size_Type), Expression (N))));
 136
 137             --  For Storage_Size for an access type, create a variable to hold
 138             --  the value of the specified size with name typeV and expand an
 139             --  assignment statement to initialze this value.
 140
 141             elsif Is_Access_Type (Ent) then
 142
 143                V := Make_Defining_Identifier (Loc,
 144                       New_External_Name (Chars (Ent), 'V'));
 145
 146                Insert_Action (N,
 147                  Make_Object_Declaration (Loc,
 148                    Defining_Identifier => V,
 149                    Object_Definition  =>
 150                      New_Reference_To (RTE (RE_Storage_Offset), Loc),
 151                    Expression =>
 152                      Convert_To (RTE (RE_Storage_Offset), Expression (N))));
 153
 154                Set_Storage_Size_Variable (Ent, Entity_Id (V));
 155             end if;
 156
 157          --  Other attributes require no expansion
 158
 159          when others =>
 160             null;
 161
 162       end case;
 163
 164    end Expand_N_Attribute_Definition_Clause;
 165
 166    -------------------------------------
 167    -- Expand_External_Tag_Definition --
 168    -------------------------------------
 169
 170    procedure Expand_External_Tag_Definition (N : Node_Id) is
 171       Loc     : constant Source_Ptr := Sloc (N);
 172       Ent     : constant Entity_Id  := Entity (Name (N));
 173       Old_Val : constant String_Id  := Strval (Expr_Value_S (Expression (N)));
 174       New_Val : String_Id;
 175       E       : Entity_Id;
 176
 177    begin
 178       --  For the rep clause "for x'external_tag use y" generate:
 179
 180       --     xV : constant string := y;
 181       --     Set_External_Tag (x'tag, xV'Address);
 182       --     Register_Tag (x'tag);
 183
 184       --  note that register_tag has been delayed up to now because
 185       --  the external_tag must be set before registering.
 186
 187       --  Create a new nul terminated string if it is not already
 188
 189       if String_Length (Old_Val) > 0
 190         and then Get_String_Char (Old_Val, String_Length (Old_Val)) = 0
 191       then
 192          New_Val := Old_Val;
 193       else
 194          Start_String (Old_Val);
 195          Store_String_Char (Get_Char_Code (ASCII.NUL));
 196          New_Val := End_String;
 197       end if;
 198
 199       E :=
 200         Make_Defining_Identifier (Loc,
 201           New_External_Name (Chars (Ent), 'A'));
 202
 203       --  The generated actions must be elaborated at the subsequent
 204       --  freeze point, not at the point of the attribute definition.
 205
 206       Append_Freeze_Action (Ent,
 207         Make_Object_Declaration (Loc,
 208           Defining_Identifier => E,
 209           Constant_Present    => True,
 210           Object_Definition   =>
 211             New_Reference_To (Standard_String, Loc),
 212           Expression          =>
 213             Make_String_Literal (Loc, Strval => New_Val)));
 214
 215       Append_Freeze_Actions (Ent, New_List (
 216         Make_Procedure_Call_Statement (Loc,
 217           Name => New_Reference_To (RTE (RE_Set_External_Tag), Loc),
 218           Parameter_Associations => New_List (
 219             Make_Attribute_Reference (Loc,
 220               Attribute_Name => Name_Tag,
 221               Prefix         => New_Occurrence_Of (Ent, Loc)),
 222
 223             Make_Attribute_Reference (Loc,
 224               Attribute_Name => Name_Address,
 225               Prefix         => New_Occurrence_Of (E, Loc)))),
 226
 227         Make_Procedure_Call_Statement (Loc,
 228           Name => New_Reference_To (RTE (RE_Register_Tag), Loc),
 229           Parameter_Associations => New_List (
 230             Make_Attribute_Reference (Loc,
 231               Attribute_Name => Name_Tag,
 232               Prefix         => New_Occurrence_Of (Ent, Loc))))));
 233    end Expand_External_Tag_Definition;
 234
 235    ----------------------------
 236    -- Expand_N_Freeze_Entity --
 237    ----------------------------
 238
 239    procedure Expand_N_Freeze_Entity (N : Node_Id) is
 240       E              : constant Entity_Id := Entity (N);
 241       E_Scope        : Entity_Id;
 242       S              : Entity_Id;
 243       In_Other_Scope : Boolean;
 244       In_Outer_Scope : Boolean;
 245       Decl           : Node_Id;
 246
 247    begin
 248       --  For object, with address clause, check alignment is OK
 249
 250       if Is_Object (E) then
 251          Apply_Alignment_Check (E, N);
 252
 253       --  Only other items requiring any front end action are
 254       --  types and subprograms.
 255
 256       elsif not Is_Type (E) and then not Is_Subprogram (E) then
 257          return;
 258       end if;
 259
 260       --  Here E is a type or a subprogram
 261
 262       E_Scope := Scope (E);
 263
 264       --  This is an error protection against previous errors
 265
 266       if No (E_Scope) then
 267          return;
 268       end if;
 269
 270       --  If we are freezing entities defined in protected types, they
 271       --  belong in the enclosing scope, given that the original type
 272       --  has been expanded away. The same is true for entities in task types,
 273       --  in particular the parameter records of entries (Entities in bodies
 274       --  are all frozen within the body). If we are in the task body, this
 275       --  is a proper scope.
 276
 277       if Ekind (E_Scope) = E_Protected_Type
 278         or else (Ekind (E_Scope) = E_Task_Type
 279                    and then not Has_Completion (E_Scope))
 280       then
 281          E_Scope := Scope (E_Scope);
 282       end if;
 283
 284       S := Current_Scope;
 285       while S /= Standard_Standard and then S /= E_Scope loop
 286          S := Scope (S);
 287       end loop;
 288
 289       In_Other_Scope := not (S = E_Scope);
 290       In_Outer_Scope := (not In_Other_Scope) and then (S /= Current_Scope);
 291
 292       --  If the entity being frozen is defined in a scope that is not
 293       --  currently on the scope stack, we must establish the proper
 294       --  visibility before freezing the entity and related subprograms.
 295
 296       if In_Other_Scope then
 297          New_Scope (E_Scope);
 298          Install_Visible_Declarations (E_Scope);
 299
 300          if Ekind (E_Scope) = E_Package         or else
 301             Ekind (E_Scope) = E_Generic_Package or else
 302             Is_Protected_Type (E_Scope)         or else
 303             Is_Task_Type (E_Scope)
 304          then
 305             Install_Private_Declarations (E_Scope);
 306          end if;
 307
 308       --  If the entity is in an outer scope, then that scope needs to
 309       --  temporarily become the current scope so that operations created
 310       --  during type freezing will be declared in the right scope and
 311       --  can properly override any corresponding inherited operations.
 312
 313       elsif In_Outer_Scope then
 314          New_Scope (E_Scope);
 315       end if;
 316
 317       --  If type, freeze the type
 318
 319       if Is_Type (E) then
 320          Freeze_Type (N);
 321
 322          --  And for enumeration type, build the enumeration tables
 323
 324          if Is_Enumeration_Type (E) then
 325             Build_Enumeration_Image_Tables (E, N);
 326
 327          elsif Is_Tagged_Type (E)
 328            and then Is_First_Subtype (E)
 329          then
 330             --  Check for a definition of External_Tag, whose expansion must
 331             --  be delayed until the dispatch table is built. The clause
 332             --  is considered only if it applies to this specific tagged
 333             --  type, as opposed to one of its ancestors.
 334
 335             declare
 336                Def : constant Node_Id :=
 337                        Get_Attribute_Definition_Clause
 338                          (E, Attribute_External_Tag);
 339
 340             begin
 341                if Present (Def) and then Entity (Name (Def)) = E then
 342                   Expand_External_Tag_Definition (Def);
 343                end if;
 344             end;
 345          end if;
 346
 347       --  If subprogram, freeze the subprogram
 348
 349       elsif Is_Subprogram (E) then
 350          Freeze_Subprogram (N);
 351       end if;
 352
 353       --  Analyze actions generated by freezing. The init_proc contains
 354       --  source expressions that may raise constraint_error, and the
 355       --  assignment procedure for complex types needs checks on individual
 356       --  component assignments, but all other freezing actions should be
 357       --  compiled with all checks off.
 358
 359       if Present (Actions (N)) then
 360          Decl := First (Actions (N));
 361
 362          while Present (Decl) loop
 363
 364             if Nkind (Decl) = N_Subprogram_Body
 365               and then (Is_Init_Proc (Defining_Entity (Decl))
 366                           or else
 367                             Chars (Defining_Entity (Decl)) = Name_uAssign)
 368             then
 369                Analyze (Decl);
 370
 371             --  A subprogram body created for a renaming_as_body completes
 372             --  a previous declaration, which may be in a different scope.
 373             --  Establish the proper scope before analysis.
 374
 375             elsif Nkind (Decl) = N_Subprogram_Body
 376               and then Present (Corresponding_Spec (Decl))
 377               and then Scope (Corresponding_Spec (Decl)) /= Current_Scope
 378             then
 379                New_Scope (Scope (Corresponding_Spec (Decl)));
 380                Analyze (Decl, Suppress => All_Checks);
 381                Pop_Scope;
 382
 383             else
 384                Analyze (Decl, Suppress => All_Checks);
 385             end if;
 386
 387             Next (Decl);
 388          end loop;
 389       end if;
 390
 391       if In_Other_Scope then
 392          if Ekind (Current_Scope) = E_Package then
 393             End_Package_Scope (E_Scope);
 394          else
 395             End_Scope;
 396          end if;
 397
 398       elsif In_Outer_Scope then
 399          Pop_Scope;
 400       end if;
 401    end Expand_N_Freeze_Entity;
 402
 403    -------------------------------------------
 404    -- Expand_N_Record_Representation_Clause --
 405    -------------------------------------------
 406
 407    --  The only expansion required is for the case of a mod clause present,
 408    --  which is removed, and translated into an alignment representation
 409    --  clause inserted immediately after the record rep clause with any
 410    --  initial pragmas inserted at the start of the component clause list.
 411
 412    procedure Expand_N_Record_Representation_Clause (N : Node_Id) is
 413       Loc     : constant Source_Ptr := Sloc (N);
 414       Rectype : constant Entity_Id  := Entity (Identifier (N));
 415       Mod_Val : Uint;
 416       Citems  : List_Id;
 417       Repitem : Node_Id;
 418       AtM_Nod : Node_Id;
 419
 420    begin
 421       if Present (Mod_Clause (N)) then
 422          Mod_Val := Expr_Value (Expression (Mod_Clause (N)));
 423          Citems  := Pragmas_Before (Mod_Clause (N));
 424
 425          if Present (Citems) then
 426             Append_List_To (Citems, Component_Clauses (N));
 427             Set_Component_Clauses (N, Citems);
 428          end if;
 429
 430          AtM_Nod :=
 431            Make_Attribute_Definition_Clause (Loc,
 432              Name       => New_Reference_To (Base_Type (Rectype), Loc),
 433              Chars      => Name_Alignment,
 434              Expression => Make_Integer_Literal (Loc, Mod_Val));
 435
 436          Set_From_At_Mod (AtM_Nod);
 437          Insert_After (N, AtM_Nod);
 438          Set_Mod_Clause (N, Empty);
 439       end if;
 440
 441       --  If the record representation clause has no components, then
 442       --  completely remove it.  Note that we also have to remove
 443       --  ourself from the Rep Item list.
 444
 445       if Is_Empty_List (Component_Clauses (N)) then
 446          if First_Rep_Item (Rectype) = N then
 447             Set_First_Rep_Item (Rectype, Next_Rep_Item (N));
 448          else
 449             Repitem := First_Rep_Item (Rectype);
 450             while Present (Next_Rep_Item (Repitem)) loop
 451                if Next_Rep_Item (Repitem) = N then
 452                   Set_Next_Rep_Item (Repitem, Next_Rep_Item (N));
 453                   exit;
 454                end if;
 455
 456                Next_Rep_Item (Repitem);
 457             end loop;
 458          end if;
 459
 460          Rewrite (N,
 461            Make_Null_Statement (Loc));
 462       end if;
 463    end Expand_N_Record_Representation_Clause;
 464
 465 end Exp_Ch13;