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------------------------------------------------------------------------------

--                                                                          --

--                         GNAT COMPILER COMPONENTS                         --

--                                                                          --

--                              S E M _ A U X                               --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 1992-2011, Free Software Foundation, Inc.         --

--                                                                          --

-- GNAT is free software;  you can  redistribute it  and/or modify it under --

-- terms of the  GNU General Public License as published  by the Free Soft- --

-- ware  Foundation;  either version 3,  or (at your option) any later ver- --

-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --

-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --

-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --

-- for  more details.  You should have  received  a copy of the GNU General --

-- Public License  distributed with GNAT; see file COPYING3.  If not, go to --

-- http://www.gnu.org/licenses for a complete copy of the license.          --

--                                                                          --

-- As a special exception,  if other files  instantiate  generics from this --

-- unit, or you link  this unit with other files  to produce an executable, --

-- this  unit  does not  by itself cause  the resulting  executable  to  be --

-- covered  by the  GNU  General  Public  License.  This exception does not --

-- however invalidate  any other reasons why  the executable file  might be --

-- covered by the  GNU Public License.                                      --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

------------------------------------------------------------------------------

--  Package containing utility procedures used throughout the compiler,

--  and also by ASIS so dependencies are limited to ASIS included packages.

--  Historical note. Many of the routines here were originally in Einfo, but

--  Einfo is supposed to be a relatively low level package dealing with the

--  content of entities in the tree, so this package is used for routines that

--  require more than minimal semantic knowledge.

with Alloc; use Alloc;

with Table;

with Types; use Types;

package Sem_Aux is

   --------------------------------

   -- Obsolescent Warnings Table --

   --------------------------------

   --  This table records entities for which a pragma Obsolescent with a

   --  message argument has been processed.

   type OWT_Record is record

      Ent : Entity_Id;

      --  The entity to which the pragma applies

      Msg : String_Id;

      --  The string containing the message

   end record;

   package Obsolescent_Warnings is new Table.Table (

     Table_Component_Type => OWT_Record,

     Table_Index_Type     => Int,

     Table_Low_Bound      => 0,

     Table_Initial        => Alloc.Obsolescent_Warnings_Initial,

     Table_Increment      => Alloc.Obsolescent_Warnings_Increment,

     Table_Name           => "Obsolescent_Warnings");

   procedure Initialize;

   --  Called at the start of compilation of each new main source file to

   --  initialize the allocation of the Obsolescent_Warnings table. Note that

   --  Initialize must not be called if Tree_Read is used.

   procedure Tree_Read;

   --  Initializes Obsolescent_Warnings table from current tree file using the

   --  relevant Table.Tree_Read routine.

   procedure Tree_Write;

   --  Writes out Obsolescent_Warnings table to current tree file using the

   --  relevant Table.Tree_Write routine.

   -----------------

   -- Subprograms --

   -----------------

   function Ancestor_Subtype (Typ : Entity_Id) return Entity_Id;

   --  The argument Id is a type or subtype entity. If the argument is a

   --  subtype then it returns the subtype or type from which the subtype was

   --  obtained, otherwise it returns Empty.

   function Available_View (Typ : Entity_Id) return Entity_Id;

   --  Typ is typically a type that has the With_Type flag set. Returns the

   --  non-limited view of the type, if available, otherwise the type itself.

   --  For class-wide types, there is no direct link in the tree, so we have

   --  to retrieve the class-wide type of the non-limited view of the Etype.

   --  Returns the argument unchanged if it is not one of these cases.

   function Constant_Value (Ent : Entity_Id) return Node_Id;

   --  Ent is a variable, constant, named integer, or named real entity. This

   --  call obtains the initialization expression for the entity. Will return

   --  Empty for for a deferred constant whose full view is not available or

   --  in some other cases of internal entities, which cannot be treated as

   --  constants from the point of view of constant folding. Empty is also

   --  returned for variables with no initialization expression.

   function Effectively_Has_Constrained_Partial_View

     (Typ  : Entity_Id;

      Scop : Entity_Id) return Boolean;

   --  Return True if Typ has attribute Has_Constrained_Partial_View set to

   --  True; in addition, within a generic body, return True if a subtype is

   --  a descendant of an untagged generic formal private or derived type, and

   --  the subtype is not an unconstrained array subtype (RM 3.3(23.10/3)).

   function Enclosing_Dynamic_Scope (Ent : Entity_Id) return Entity_Id;

   --  For any entity, Ent, returns the closest dynamic scope in which the

   --  entity is declared or Standard_Standard for library-level entities.

   function First_Discriminant (Typ : Entity_Id) return Entity_Id;

   --  Typ is a type with discriminants. The discriminants are the first

   --  entities declared in the type, so normally this is equivalent to

   --  First_Entity. The exception arises for tagged types, where the tag

   --  itself is prepended to the front of the entity chain, so the

   --  First_Discriminant function steps past the tag if it is present.

   function First_Stored_Discriminant (Typ : Entity_Id) return Entity_Id;

   --  Typ is a type with discriminants. Gives the first discriminant stored

   --  in an object of this type. In many cases, these are the same as the

   --  normal visible discriminants for the type, but in the case of renamed

   --  discriminants, this is not always the case.

   --

   --  For tagged types, and untagged types which are root types or derived

   --  types but which do not rename discriminants in their root type, the

   --  stored discriminants are the same as the actual discriminants of the

   --  type, and hence this function is the same as First_Discriminant.

   --

   --  For derived non-tagged types that rename discriminants in the root type

   --  this is the first of the discriminants that occur in the root type. To

   --  be precise, in this case stored discriminants are entities attached to

   --  the entity chain of the derived type which are a copy of the

   --  discriminants of the root type. Furthermore their Is_Completely_Hidden

   --  flag is set since although they are actually stored in the object, they

   --  are not in the set of discriminants that is visible in the type.

   --

   --  For derived untagged types, the set of stored discriminants are the real

   --  discriminants from Gigi's standpoint, i.e. those that will be stored in

   --  actual objects of the type.

   function First_Subtype (Typ : Entity_Id) return Entity_Id;

   --  Applies to all types and subtypes. For types, yields the first subtype

   --  of the type. For subtypes, yields the first subtype of the base type of

   --  the subtype.

   function First_Tag_Component (Typ : Entity_Id) return Entity_Id;

   --  Typ must be a tagged record type. This function returns the Entity for

   --  the first _Tag field in the record type.

   function In_Generic_Body (Id : Entity_Id) return Boolean;

   --  Determine whether entity Id appears inside a generic body

   function Is_By_Copy_Type (Ent : Entity_Id) return Boolean;

   --  Ent is any entity. Returns True if Ent is a type entity where the type

   --  is required to be passed by copy, as defined in (RM 6.2(3)).

   function Is_By_Reference_Type (Ent : Entity_Id) return Boolean;

   --  Ent is any entity. Returns True if Ent is a type entity where the type

   --  is required to be passed by reference, as defined in (RM 6.2(4-9)).

   function Is_Derived_Type (Ent : Entity_Id) return Boolean;

   --  Determines if the given entity Ent is a derived type. Result is always

   --  false if argument is not a type.

   function Is_Generic_Formal (E : Entity_Id) return Boolean;

   --  Determine whether E is a generic formal parameter. In particular this is

   --  used to set the visibility of generic formals of a generic package

   --  declared with a box or with partial parametrization.

   function Is_Indefinite_Subtype (Ent : Entity_Id) return Boolean;

   --  Ent is any entity. Determines if given entity is an unconstrained array

   --  type or subtype, a discriminated record type or subtype with no initial

   --  discriminant values or a class wide type or subtype and returns True if

   --  so. False for other type entities, or any entities that are not types.

   function Is_Immutably_Limited_Type (Ent : Entity_Id) return Boolean;

   --  Ent is any entity. True for a type that is "inherently" limited (i.e.

   --  cannot become nonlimited). From the Ada 2005 RM-7.5(8.1/2), "a type with

   --  a part that is of a task, protected, or explicitly limited record type".

   --  These are the types that are defined as return-by-reference types in Ada

   --  95 (see RM95-6.5(11-16)). In Ada 2005, these are the types that require

   --  build-in-place for function calls. Note that build-in-place is allowed

   --  for other types, too. This is also used for identifying pure procedures

   --  whose calls should not be eliminated (RM 10.2.1(18/2)).

   function Is_Limited_Type (Ent : Entity_Id) return Boolean;

   --  Ent is any entity. Returns true if Ent is a limited type (limited

   --  private type, limited interface type, task type, protected type,

   --  composite containing a limited component, or a subtype of any of

   --  these types).

   function Nearest_Ancestor (Typ : Entity_Id) return Entity_Id;

   --  Given a subtype Typ, this function finds out the nearest ancestor from

   --  which constraints and predicates are inherited. There is no simple link

   --  for doing this, consider:

   --

   --     subtype R is Integer range 1 .. 10;

   --     type T is new R;

   --

   --  In this case the nearest ancestor is R, but the Etype of T'Base will

   --  point to R'Base, so we have to go rummaging in the declarations to get

   --  this information. It is used for making sure we freeze this before we

   --  freeze Typ, and also for retrieving inherited predicate information.

   --  For the case of base types or first subtypes, there is no useful entity

   --  to return, so Empty is returned.

   --

   --  Note: this is similar to Ancestor_Subtype except that it also deals

   --  with the case of derived types.

   function Nearest_Dynamic_Scope (Ent : Entity_Id) return Entity_Id;

   --  This is similar to Enclosing_Dynamic_Scope except that if Ent is itself

   --  a dynamic scope, then it is returned. Otherwise the result is the same

   --  as that returned by Enclosing_Dynamic_Scope.

   function Next_Tag_Component (Tag : Entity_Id) return Entity_Id;

   --  Tag must be an entity representing a _Tag field of a tagged record.

   --  The result returned is the next _Tag field in this record, or Empty

   --  if this is the last such field.

   function Number_Discriminants (Typ : Entity_Id) return Pos;

   --  Typ is a type with discriminants, yields number of discriminants in type

   function Initialization_Suppressed (Typ : Entity_Id) return Boolean;

   pragma Inline (Initialization_Suppressed);

   --  Returns True if initialization should be suppressed for the given type

   --  or subtype. This is true if Suppress_Initialization is set either for

   --  the subtype itself, or for the corresponding base type.

   function Ultimate_Alias (Prim : Entity_Id) return Entity_Id;

   pragma Inline (Ultimate_Alias);

   --  Return the last entity in the chain of aliased entities of Prim. If Prim

   --  has no alias return Prim.

   function Unit_Declaration_Node (Unit_Id : Entity_Id) return Node_Id;

   --  Unit_Id is the simple name of a program unit, this function returns the

   --  corresponding xxx_Declaration node for the entity. Also applies to the

   --  body entities for subprograms, tasks and protected units, in which case

   --  it returns the subprogram, task or protected body node for it. The unit

   --  may be a child unit with any number of ancestors.

end Sem_Aux;