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) 1992-2019, 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.  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 COPYING3.  If not, go to --
19-- http://www.gnu.org/licenses for a complete copy of the license.          --
20--                                                                          --
21-- GNAT was originally developed  by the GNAT team at  New York University. --
22-- Extensive contributions were provided by Ada Core Technologies Inc.      --
23--                                                                          --
24------------------------------------------------------------------------------
25
26with Atree;    use Atree;
27with Checks;   use Checks;
28with Einfo;    use Einfo;
29with Exp_Ch3;  use Exp_Ch3;
30with Exp_Ch6;
31with Exp_Imgv; use Exp_Imgv;
32with Exp_Tss;  use Exp_Tss;
33with Exp_Util; use Exp_Util;
34with Freeze;   use Freeze;
35with Namet;    use Namet;
36with Nlists;   use Nlists;
37with Nmake;    use Nmake;
38with Opt;      use Opt;
39with Restrict; use Restrict;
40with Rident;   use Rident;
41with Rtsfind;  use Rtsfind;
42with Sem;      use Sem;
43with Sem_Aux;  use Sem_Aux;
44with Sem_Ch7;  use Sem_Ch7;
45with Sem_Ch8;  use Sem_Ch8;
46with Sem_Eval; use Sem_Eval;
47with Sem_Util; use Sem_Util;
48with Sinfo;    use Sinfo;
49with Snames;   use Snames;
50with Tbuild;   use Tbuild;
51with Uintp;    use Uintp;
52with Validsw;  use Validsw;
53
54package body Exp_Ch13 is
55
56   ------------------------------------------
57   -- Expand_N_Attribute_Definition_Clause --
58   ------------------------------------------
59
60   --  Expansion action depends on attribute involved
61
62   procedure Expand_N_Attribute_Definition_Clause (N : Node_Id) is
63      Loc : constant Source_Ptr := Sloc (N);
64      Exp : constant Node_Id    := Expression (N);
65      Ent : Entity_Id;
66      V   : Node_Id;
67
68   begin
69      Ent := Entity (Name (N));
70
71      if Is_Type (Ent) then
72         Ent := Underlying_Type (Ent);
73      end if;
74
75      case Get_Attribute_Id (Chars (N)) is
76
77         -------------
78         -- Address --
79         -------------
80
81         when Attribute_Address =>
82
83            --  If there is an initialization which did not come from the
84            --  source program, then it is an artifact of our expansion, and we
85            --  suppress it. The case we are most concerned about here is the
86            --  initialization of a packed array to all false, which seems
87            --  inappropriate for variable to which an address clause is
88            --  applied. The expression may itself have been rewritten if the
89            --  type is packed array, so we need to examine whether the
90            --  original node is in the source. An exception though is the case
91            --  of an access variable which is default initialized to null, and
92            --  such initialization is retained.
93
94            --  Furthermore, if the initialization is the equivalent aggregate
95            --  of the type initialization procedure, it replaces an implicit
96            --  call to the init proc, and must be respected. Note that for
97            --  packed types we do not build equivalent aggregates.
98
99            --  Also, if Init_Or_Norm_Scalars applies, then we need to retain
100            --  any default initialization for objects of scalar types and
101            --  types with scalar components. Normally a composite type will
102            --  have an init_proc in the presence of Init_Or_Norm_Scalars,
103            --  so when that flag is set we have just have to do a test for
104            --  scalar and string types (the predefined string types such as
105            --  String and Wide_String don't have an init_proc).
106
107            declare
108               Decl : constant Node_Id := Declaration_Node (Ent);
109               Typ  : constant Entity_Id := Etype (Ent);
110
111            begin
112               if Nkind (Decl) = N_Object_Declaration
113                  and then Present (Expression (Decl))
114                  and then Nkind (Expression (Decl)) /= N_Null
115                  and then
116                    not Comes_From_Source (Original_Node (Expression (Decl)))
117               then
118                  if Present (Base_Init_Proc (Typ))
119                    and then
120                      Present (Static_Initialization (Base_Init_Proc (Typ)))
121                  then
122                     null;
123
124                  elsif Init_Or_Norm_Scalars
125                    and then (Is_Scalar_Type (Typ)
126                               or else Is_String_Type (Typ))
127                  then
128                     null;
129
130                  else
131                     Set_Expression (Decl, Empty);
132                  end if;
133
134               --  An object declaration to which an address clause applies
135               --  has a delayed freeze, but the address expression itself
136               --  must be elaborated at the point it appears. If the object
137               --  is controlled, additional checks apply elsewhere.
138               --  If the attribute comes from an aspect specification it
139               --  is being elaborated at the freeze point and side effects
140               --  need not be removed (and shouldn't, if the expression
141               --  depends on other entities that have delayed freeze).
142               --  This is another consequence of the delayed analysis of
143               --  aspects, and a real semantic difference.
144
145               elsif Nkind (Decl) = N_Object_Declaration
146                 and then not Needs_Constant_Address (Decl, Typ)
147                 and then not From_Aspect_Specification (N)
148               then
149                  Remove_Side_Effects (Exp);
150               end if;
151            end;
152
153         ---------------
154         -- Alignment --
155         ---------------
156
157         when Attribute_Alignment =>
158
159            --  As required by Gigi, we guarantee that the operand is an
160            --  integer literal (this simplifies things in Gigi).
161
162            if Nkind (Exp) /= N_Integer_Literal then
163               Rewrite (Exp, Make_Integer_Literal (Loc, Expr_Value (Exp)));
164            end if;
165
166            --  A complex case arises if the alignment clause applies to an
167            --  unconstrained object initialized with a function call. The
168            --  result of the call is placed on the secondary stack, and the
169            --  declaration is rewritten as a renaming of a dereference, which
170            --  fails expansion. We must introduce a temporary and assign its
171            --  value to the existing entity.
172
173            if Nkind (Parent (Ent)) = N_Object_Renaming_Declaration
174              and then not Is_Entity_Name (Renamed_Object (Ent))
175            then
176               declare
177                  Decl : constant Node_Id    := Parent (Ent);
178                  Loc  : constant Source_Ptr := Sloc (N);
179                  Temp : constant Entity_Id  := Make_Temporary (Loc, 'T');
180
181                  New_Decl : Node_Id;
182
183               begin
184                  --  Replace entity with temporary and reanalyze
185
186                  Set_Defining_Identifier (Decl, Temp);
187                  Set_Analyzed (Decl, False);
188                  Analyze (Decl);
189
190                  --  Introduce new declaration for entity but do not reanalyze
191                  --  because entity is already in scope. Type and expression
192                  --  are already resolved.
193
194                  New_Decl :=
195                    Make_Object_Declaration (Loc,
196                      Defining_Identifier => Ent,
197                      Object_Definition   =>
198                        New_Occurrence_Of (Etype (Ent), Loc),
199                      Expression          => New_Occurrence_Of (Temp, Loc));
200
201                  Set_Renamed_Object (Ent, Empty);
202                  Insert_After (Decl, New_Decl);
203                  Set_Analyzed (Decl);
204               end;
205            end if;
206
207         ------------------
208         -- Storage_Size --
209         ------------------
210
211         when Attribute_Storage_Size =>
212
213            --  If the type is a task type, then assign the value of the
214            --  storage size to the Size variable associated with the task.
215            --  Insert the assignment right after the declaration of the Size
216            --  variable.
217
218            --  Generate:
219
220            --  task_typeZ := expression
221
222            if Ekind (Ent) = E_Task_Type then
223
224               declare
225                  Assign : Node_Id;
226               begin
227                  Assign :=
228                    Make_Assignment_Statement (Loc,
229                      Name       =>
230                        New_Occurrence_Of (Storage_Size_Variable (Ent), Loc),
231                      Expression =>
232                        Convert_To (RTE (RE_Size_Type), Expression (N)));
233
234                  --  If the clause is not generated by an aspect, insert
235                  --  the assignment here. Freezing rules ensure that this
236                  --  is safe, or clause will have been rejected already.
237
238                  if Is_List_Member (N) then
239                     Insert_After (N, Assign);
240
241                  --  Otherwise, insert assignment after task declaration.
242
243                  else
244                     Insert_After
245                       (Parent (Storage_Size_Variable (Entity (N))), Assign);
246                  end if;
247
248                  Analyze (Assign);
249               end;
250
251            --  For Storage_Size for an access type, create a variable to hold
252            --  the value of the specified size with name typeV and expand an
253            --  assignment statement to initialize this value.
254
255            elsif Is_Access_Type (Ent) then
256
257               --  We don't need the variable for a storage size of zero
258
259               if not No_Pool_Assigned (Ent) then
260                  V :=
261                    Make_Defining_Identifier (Loc,
262                      Chars => New_External_Name (Chars (Ent), 'V'));
263
264                  --  Insert the declaration of the object. If the expression
265                  --  is not static it may depend on some other type that is
266                  --  not frozen yet, so attach the declaration that captures
267                  --  the value of the expression to the actions of the freeze
268                  --  node of the current type.
269
270                  declare
271                     Decl : constant Node_Id :=
272                       Make_Object_Declaration (Loc,
273                         Defining_Identifier => V,
274                         Object_Definition   =>
275                           New_Occurrence_Of (RTE (RE_Storage_Offset), Loc),
276                         Expression          =>
277                           Convert_To
278                             (RTE (RE_Storage_Offset), Expression (N)));
279                  begin
280                     if not Is_OK_Static_Expression (Expression (N))
281                       and then Present (Freeze_Node (Ent))
282                     then
283                        if No (Actions (Freeze_Node (Ent))) then
284                           Set_Actions (Freeze_Node (Ent), New_List (Decl));
285                        else
286                           Append (Decl, Actions (Freeze_Node (Ent)));
287                        end if;
288
289                     else
290                        Insert_Action (N, Decl);
291                     end if;
292                  end;
293
294                  Set_Storage_Size_Variable (Ent, Entity_Id (V));
295               end if;
296            end if;
297
298         --  Other attributes require no expansion
299
300         when others =>
301            null;
302      end case;
303   end Expand_N_Attribute_Definition_Clause;
304
305   -----------------------------
306   -- Expand_N_Free_Statement --
307   -----------------------------
308
309   procedure Expand_N_Free_Statement (N : Node_Id) is
310      Expr : constant Node_Id := Expression (N);
311      Typ  : Entity_Id;
312
313   begin
314      --  Certain run-time configurations and targets do not provide support
315      --  for controlled types.
316
317      if Restriction_Active (No_Finalization) then
318         return;
319      end if;
320
321      --  Use the base type to perform the check for finalization master
322
323      Typ := Etype (Expr);
324
325      if Ekind (Typ) = E_Access_Subtype then
326         Typ := Etype (Typ);
327      end if;
328
329      --  Handle private access types
330
331      if Is_Private_Type (Typ)
332        and then Present (Full_View (Typ))
333      then
334         Typ := Full_View (Typ);
335      end if;
336
337      --  Do not create a custom Deallocate when freeing an object with
338      --  suppressed finalization. In such cases the object is never attached
339      --  to a master, so it does not need to be detached. Use a regular free
340      --  statement instead.
341
342      if No (Finalization_Master (Typ)) then
343         return;
344      end if;
345
346      --  Use a temporary to store the result of a complex expression. Perform
347      --  the following transformation:
348      --
349      --     Free (Complex_Expression);
350      --
351      --     Temp : constant Type_Of_Expression := Complex_Expression;
352      --     Free (Temp);
353
354      if Nkind (Expr) /= N_Identifier then
355         declare
356            Expr_Typ : constant Entity_Id  := Etype (Expr);
357            Loc      : constant Source_Ptr := Sloc (N);
358            New_Expr : Node_Id;
359            Temp_Id  : Entity_Id;
360
361         begin
362            Temp_Id := Make_Temporary (Loc, 'T');
363            Insert_Action (N,
364              Make_Object_Declaration (Loc,
365                Defining_Identifier => Temp_Id,
366                Object_Definition   => New_Occurrence_Of (Expr_Typ, Loc),
367                Expression          => Relocate_Node (Expr)));
368
369            New_Expr := New_Occurrence_Of (Temp_Id, Loc);
370            Set_Etype (New_Expr, Expr_Typ);
371
372            Set_Expression (N, New_Expr);
373         end;
374      end if;
375
376      --  Create a custom Deallocate for a controlled object. This routine
377      --  ensures that the hidden list header will be deallocated along with
378      --  the actual object.
379
380      Build_Allocate_Deallocate_Proc (N, Is_Allocate => False);
381   end Expand_N_Free_Statement;
382
383   ----------------------------
384   -- Expand_N_Freeze_Entity --
385   ----------------------------
386
387   procedure Expand_N_Freeze_Entity (N : Node_Id) is
388      E : constant Entity_Id := Entity (N);
389
390      Decl           : Node_Id;
391      Delete         : Boolean := False;
392      E_Scope        : Entity_Id;
393      In_Other_Scope : Boolean;
394      In_Outer_Scope : Boolean;
395
396   begin
397      --  If there are delayed aspect specifications, we insert them just
398      --  before the freeze node. They are already analyzed so we don't need
399      --  to reanalyze them (they were analyzed before the type was frozen),
400      --  but we want them in the tree for the back end, and so that the
401      --  listing from sprint is clearer on where these occur logically.
402
403      if Has_Delayed_Aspects (E) then
404         declare
405            Aitem : Node_Id;
406            Ritem : Node_Id;
407
408         begin
409            --  Look for aspect specs for this entity
410
411            Ritem := First_Rep_Item (E);
412            while Present (Ritem) loop
413               if Nkind (Ritem) = N_Aspect_Specification
414                 and then Entity (Ritem) = E
415               then
416                  Aitem := Aspect_Rep_Item (Ritem);
417
418                  --  Skip this for aspects (e.g. Current_Value) for which
419                  --  there is no corresponding pragma or attribute.
420
421                  if Present (Aitem)
422
423                    --  Also skip if we have a null statement rather than a
424                    --  delayed aspect (this happens when we are ignoring rep
425                    --  items from use of the -gnatI switch).
426
427                    and then Nkind (Aitem) /= N_Null_Statement
428                  then
429                     pragma Assert (Is_Delayed_Aspect (Aitem));
430                     Insert_Before (N, Aitem);
431                  end if;
432               end if;
433
434               Next_Rep_Item (Ritem);
435            end loop;
436         end;
437      end if;
438
439      --  Processing for objects
440
441      if Is_Object (E) then
442         if Present (Address_Clause (E)) then
443            Apply_Address_Clause_Check (E, N);
444         end if;
445
446         --  Analyze actions in freeze node, if any
447
448         if Present (Actions (N)) then
449            declare
450               Act : Node_Id;
451            begin
452               Act := First (Actions (N));
453               while Present (Act) loop
454                  Analyze (Act);
455                  Next (Act);
456               end loop;
457            end;
458         end if;
459
460         --  If initialization statements have been captured in a compound
461         --  statement, insert them back into the tree now.
462
463         Explode_Initialization_Compound_Statement (E);
464         return;
465
466      --  Only other items requiring any front end action are types and
467      --  subprograms.
468
469      elsif not Is_Type (E) and then not Is_Subprogram (E) then
470         return;
471      end if;
472
473      --  Here E is a type or a subprogram
474
475      E_Scope := Scope (E);
476
477      --  This is an error protection against previous errors
478
479      if No (E_Scope) then
480         Check_Error_Detected;
481         return;
482      end if;
483
484      --  The entity may be a subtype declared for a constrained record
485      --  component, in which case the relevant scope is the scope of
486      --  the record. This happens for class-wide subtypes created for
487      --  a constrained type extension with inherited discriminants.
488
489      if Is_Type (E_Scope)
490        and then Ekind (E_Scope) not in Concurrent_Kind
491      then
492         E_Scope := Scope (E_Scope);
493
494      --  The entity may be a subtype declared for an iterator
495
496      elsif Ekind (E_Scope) = E_Loop then
497         E_Scope := Scope (E_Scope);
498      end if;
499
500      --  Remember that we are processing a freezing entity and its freezing
501      --  nodes. This flag (non-zero = set) is used to avoid the need of
502      --  climbing through the tree while processing the freezing actions (ie.
503      --  to avoid generating spurious warnings or to avoid killing constant
504      --  indications while processing the code associated with freezing
505      --  actions). We use a counter to deal with nesting.
506
507      Inside_Freezing_Actions := Inside_Freezing_Actions + 1;
508
509      --  If we are freezing entities defined in protected types, they belong
510      --  in the enclosing scope, given that the original type has been
511      --  expanded away. The same is true for entities in task types, in
512      --  particular the parameter records of entries (Entities in bodies are
513      --  all frozen within the body). If we are in the task body, this is a
514      --  proper scope. If we are within a subprogram body, the proper scope
515      --  is the corresponding spec. This may happen for itypes generated in
516      --  the bodies of protected operations.
517
518      if Ekind (E_Scope) = E_Protected_Type
519        or else (Ekind (E_Scope) = E_Task_Type
520                  and then not Has_Completion (E_Scope))
521      then
522         E_Scope := Scope (E_Scope);
523
524      elsif Ekind (E_Scope) = E_Subprogram_Body then
525         E_Scope := Corresponding_Spec (Unit_Declaration_Node (E_Scope));
526      end if;
527
528      --  If the scope of the entity is in open scopes, it is the current one
529      --  or an enclosing one, including a loop, a block, or a subprogram.
530
531      if In_Open_Scopes (E_Scope) then
532         In_Other_Scope := False;
533         In_Outer_Scope := E_Scope /= Current_Scope;
534
535      --  Otherwise it is a local package or a different compilation unit
536
537      else
538         In_Other_Scope := True;
539         In_Outer_Scope := False;
540      end if;
541
542      --  If the entity being frozen is defined in a scope that is not
543      --  currently on the scope stack, we must establish the proper
544      --  visibility before freezing the entity and related subprograms.
545
546      if In_Other_Scope then
547         Push_Scope (E_Scope);
548
549         --  Finalizers are little odd in terms of freezing. The spec of the
550         --  procedure appears in the declarations while the body appears in
551         --  the statement part of a single construct. Since the finalizer must
552         --  be called by the At_End handler of the construct, the spec is
553         --  manually frozen right after its declaration. The only side effect
554         --  of this action appears in contexts where the construct is not in
555         --  its final resting place. These contexts are:
556
557         --    * Entry bodies - The declarations and statements are moved to
558         --      the procedure equivalen of the entry.
559         --    * Protected subprograms - The declarations and statements are
560         --      moved to the non-protected version of the subprogram.
561         --    * Task bodies - The declarations and statements are moved to the
562         --      task body procedure.
563         --    * Blocks that will be rewritten as subprograms when unnesting
564         --      is in effect.
565
566         --  Visible declarations do not need to be installed in these three
567         --  cases since it does not make semantic sense to do so. All entities
568         --  referenced by a finalizer are visible and already resolved, plus
569         --  the enclosing scope may not have visible declarations at all.
570
571         if Ekind (E) = E_Procedure
572           and then Is_Finalizer (E)
573           and then
574             (Is_Entry (E_Scope)
575                or else (Is_Subprogram (E_Scope)
576                          and then Is_Protected_Type (Scope (E_Scope)))
577                or else Is_Task_Type (E_Scope)
578                or else Ekind (E_Scope) = E_Block)
579         then
580            null;
581         else
582            Install_Visible_Declarations (E_Scope);
583         end if;
584
585         if Is_Package_Or_Generic_Package (E_Scope) or else
586            Is_Protected_Type (E_Scope)             or else
587            Is_Task_Type (E_Scope)
588         then
589            Install_Private_Declarations (E_Scope);
590         end if;
591
592      --  If the entity is in an outer scope, then that scope needs to
593      --  temporarily become the current scope so that operations created
594      --  during type freezing will be declared in the right scope and
595      --  can properly override any corresponding inherited operations.
596
597      elsif In_Outer_Scope then
598         Push_Scope (E_Scope);
599      end if;
600
601      --  If type, freeze the type
602
603      if Is_Type (E) then
604         Delete := Freeze_Type (N);
605
606         --  And for enumeration type, build the enumeration tables
607
608         if Is_Enumeration_Type (E) then
609            Build_Enumeration_Image_Tables (E, N);
610         end if;
611
612      --  If subprogram, freeze the subprogram
613
614      elsif Is_Subprogram (E) then
615         Exp_Ch6.Freeze_Subprogram (N);
616
617         --  Ada 2005 (AI-251): Remove the freezing node associated with the
618         --  entities internally used by the frontend to register primitives
619         --  covering abstract interfaces. The call to Freeze_Subprogram has
620         --  already expanded the code that fills the corresponding entry in
621         --  its secondary dispatch table and therefore the code generator
622         --  has nothing else to do with this freezing node.
623
624         Delete := Present (Interface_Alias (E));
625      end if;
626
627      --  Analyze actions generated by freezing. The init_proc contains source
628      --  expressions that may raise Constraint_Error, and the assignment
629      --  procedure for complex types needs checks on individual component
630      --  assignments, but all other freezing actions should be compiled with
631      --  all checks off.
632
633      if Present (Actions (N)) then
634         Decl := First (Actions (N));
635         while Present (Decl) loop
636            if Nkind (Decl) = N_Subprogram_Body
637              and then (Is_Init_Proc (Defining_Entity (Decl))
638                          or else
639                            Chars (Defining_Entity (Decl)) = Name_uAssign)
640            then
641               Analyze (Decl);
642
643            --  A subprogram body created for a renaming_as_body completes
644            --  a previous declaration, which may be in a different scope.
645            --  Establish the proper scope before analysis.
646
647            elsif Nkind (Decl) = N_Subprogram_Body
648              and then Present (Corresponding_Spec (Decl))
649              and then Scope (Corresponding_Spec (Decl)) /= Current_Scope
650            then
651               Push_Scope (Scope (Corresponding_Spec (Decl)));
652               Analyze (Decl, Suppress => All_Checks);
653               Pop_Scope;
654
655            --  We treat generated equality specially, if validity checks are
656            --  enabled, in order to detect components default-initialized
657            --  with invalid values.
658
659            elsif Nkind (Decl) = N_Subprogram_Body
660              and then Chars (Defining_Entity (Decl)) = Name_Op_Eq
661              and then Validity_Checks_On
662              and then Initialize_Scalars
663            then
664               declare
665                  Save_Force : constant Boolean := Force_Validity_Checks;
666               begin
667                  Force_Validity_Checks := True;
668                  Analyze (Decl);
669                  Force_Validity_Checks := Save_Force;
670               end;
671
672            --  All other freezing actions
673
674            else
675               Analyze (Decl, Suppress => All_Checks);
676            end if;
677
678            Next (Decl);
679         end loop;
680      end if;
681
682      --  If we are to delete this N_Freeze_Entity, do so by rewriting so that
683      --  a loop on all nodes being inserted will work propertly.
684
685      if Delete then
686         Rewrite (N, Make_Null_Statement (Sloc (N)));
687      end if;
688
689      --  Pop scope if we installed one for the analysis
690
691      if In_Other_Scope then
692         if Ekind (Current_Scope) = E_Package then
693            End_Package_Scope (E_Scope);
694         else
695            End_Scope;
696         end if;
697
698      elsif In_Outer_Scope then
699         Pop_Scope;
700      end if;
701
702      --  Restore previous value of the nesting-level counter that records
703      --  whether we are inside a (possibly nested) call to this procedure.
704
705      Inside_Freezing_Actions := Inside_Freezing_Actions - 1;
706   end Expand_N_Freeze_Entity;
707
708   -------------------------------------------
709   -- Expand_N_Record_Representation_Clause --
710   -------------------------------------------
711
712   --  The only expansion required is for the case of a mod clause present,
713   --  which is removed, and translated into an alignment representation
714   --  clause inserted immediately after the record rep clause with any
715   --  initial pragmas inserted at the start of the component clause list.
716
717   procedure Expand_N_Record_Representation_Clause (N : Node_Id) is
718      Loc     : constant Source_Ptr := Sloc (N);
719      Rectype : constant Entity_Id  := Entity (Identifier (N));
720      Mod_Val : Uint;
721      Citems  : List_Id;
722      Repitem : Node_Id;
723      AtM_Nod : Node_Id;
724
725   begin
726      if Present (Mod_Clause (N)) and then not Ignore_Rep_Clauses then
727         Mod_Val := Expr_Value (Expression (Mod_Clause (N)));
728         Citems  := Pragmas_Before (Mod_Clause (N));
729
730         if Present (Citems) then
731            Append_List_To (Citems, Component_Clauses (N));
732            Set_Component_Clauses (N, Citems);
733         end if;
734
735         AtM_Nod :=
736           Make_Attribute_Definition_Clause (Loc,
737             Name       => New_Occurrence_Of (Base_Type (Rectype), Loc),
738             Chars      => Name_Alignment,
739             Expression => Make_Integer_Literal (Loc, Mod_Val));
740
741         Set_From_At_Mod (AtM_Nod);
742         Insert_After (N, AtM_Nod);
743         Set_Mod_Clause (N, Empty);
744      end if;
745
746      --  If the record representation clause has no components, then
747      --  completely remove it. Note that we also have to remove
748      --  ourself from the Rep Item list.
749
750      if Is_Empty_List (Component_Clauses (N)) then
751         if First_Rep_Item (Rectype) = N then
752            Set_First_Rep_Item (Rectype, Next_Rep_Item (N));
753         else
754            Repitem := First_Rep_Item (Rectype);
755            while Present (Next_Rep_Item (Repitem)) loop
756               if Next_Rep_Item (Repitem) = N then
757                  Set_Next_Rep_Item (Repitem, Next_Rep_Item (N));
758                  exit;
759               end if;
760
761               Next_Rep_Item (Repitem);
762            end loop;
763         end if;
764
765         Rewrite (N,
766           Make_Null_Statement (Loc));
767      end if;
768   end Expand_N_Record_Representation_Clause;
769
770end Exp_Ch13;
771