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

--                                                                          --

--                         GNAT COMPILER COMPONENTS                         --

--                                                                          --

--                                T Y P E S                                 --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 1992-2009, 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.                                     --

--                                                                          --

-- As a special exception under Section 7 of GPL version 3, you are granted --

-- additional permissions described in the GCC Runtime Library Exception,   --

-- version 3.1, as published by the Free Software Foundation.               --

--                                                                          --

-- You should have received a copy of the GNU General Public License and    --

-- a copy of the GCC Runtime Library Exception along with this program;     --

-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --

-- <http://www.gnu.org/licenses/>.                                          --

--                                                                          --

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

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

--                                                                          --

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

--  This package contains host independent type definitions which are used

--  in more than one unit in the compiler. They are gathered here for easy

--  reference, although in some cases the full description is found in the

--  relevant module which implements the definition. The main reason that they

--  are not in their "natural" specs is that this would cause a lot of inter-

--  spec dependencies, and in particular some awkward circular dependencies

--  would have to be dealt with.

--  WARNING: There is a C version of this package. Any changes to this source

--  file must be properly reflected in the C header file types.h declarations.

--  Note: the declarations in this package reflect an expectation that the host

--  machine has an efficient integer base type with a range at least 32 bits

--  2s-complement. If there are any machines for which this is not a correct

--  assumption, a significant number of changes will be required!

with System;

with Unchecked_Conversion;

with Unchecked_Deallocation;

package Types is

   pragma Preelaborate;

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

   -- General Use Integer Types --

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

   type Int is range -2 ** 31 .. +2 ** 31 - 1;

   --  Signed 32-bit integer

   type Dint is range -2 ** 63 .. +2 ** 63 - 1;

   --  Double length (64-bit) integer

   subtype Nat is Int range 0 .. Int'Last;

   --  Non-negative Int values

   subtype Pos is Int range 1 .. Int'Last;

   --  Positive Int values

   type Word is mod 2 ** 32;

   --  Unsigned 32-bit integer

   type Short is range -32768 .. +32767;

   for Short'Size use 16;

   --  16-bit signed integer

   type Byte is mod 2 ** 8;

   for Byte'Size use 8;

   --  8-bit unsigned integer

   type size_t is mod 2 ** Standard'Address_Size;

   --  Memory size value, for use in calls to C routines

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

   -- 8-Bit Character and String Types --

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

   --  We use Standard.Character and Standard.String freely, since we are

   --  compiling ourselves, and we properly implement the required 8-bit

   --  character code as required in Ada 95. This section defines a few

   --  general use constants and subtypes.

   EOF : constant Character := ASCII.SUB;

   --  The character SUB (16#1A#) is used in DOS and other systems derived

   --  from DOS (XP, NT etc) to signal the end of a text file. Internally

   --  all source files are ended by an EOF character, even on Unix systems.

   --  An EOF character acts as the end of file only as the last character

   --  of a source buffer, in any other position, it is treated as a blank

   --  if it appears between tokens, and as an illegal character otherwise.

   --  This makes life easier dealing with files that originated from DOS,

   --  including concatenated files with interspersed EOF characters.

   subtype Graphic_Character is Character range ' ' .. '~';

   --  Graphic characters, as defined in ARM

   subtype Line_Terminator is Character range ASCII.LF .. ASCII.CR;

   --  Line terminator characters (LF, VT, FF, CR)

   --

   --  This definition is dubious now that we have two more wide character

   --  sequences that constitute a line terminator. Every reference to this

   --  subtype needs checking to make sure the wide character case is handled

   --  appropriately. ???

   subtype Upper_Half_Character is

     Character range Character'Val (16#80#) .. Character'Val (16#FF#);

   --  Characters with the upper bit set

   type Character_Ptr is access all Character;

   type String_Ptr    is access all String;

   --  Standard character and string pointers

   procedure Free is new Unchecked_Deallocation (String, String_Ptr);

   --  Procedure for freeing dynamically allocated String values

   subtype Big_String is String (Positive);

   type Big_String_Ptr is access all Big_String;

   for Big_String_Ptr'Storage_Size use 0;

   --  Virtual type for handling imported big strings

   function To_Big_String_Ptr is

     new Unchecked_Conversion (System.Address, Big_String_Ptr);

   --  Used to obtain Big_String_Ptr values from external addresses

   subtype Word_Hex_String is String (1 .. 8);

   --  Type used to represent Word value as 8 hex digits, with lower case

   --  letters for the alphabetic cases.

   function Get_Hex_String (W : Word) return Word_Hex_String;

   --  Convert word value to 8-character hex string

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

   -- Types Used for Text Buffer Handling --

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

   --  We can not use type String for text buffers, since we must use the

   --  standard 32-bit integer as an index value, since we count on all index

   --  values being the same size.

   type Text_Ptr is new Int;

   --  Type used for subscripts in text buffer

   type Text_Buffer is array (Text_Ptr range <>) of Character;

   --  Text buffer used to hold source file or library information file

   type Text_Buffer_Ptr is access all Text_Buffer;

   --  Text buffers for input files are allocated dynamically and this type

   --  is used to reference these text buffers.

   procedure Free is new Unchecked_Deallocation (Text_Buffer, Text_Buffer_Ptr);

   --  Procedure for freeing dynamically allocated text buffers

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

   -- Types Used for Source Input Handling --

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

   type Logical_Line_Number is range 0 .. Int'Last;

   for Logical_Line_Number'Size use 32;

   --  Line number type, used for storing logical line numbers (i.e. line

   --  numbers that include effects of any Source_Reference pragmas in the

   --  source file). The value zero indicates a line containing a source

   --  reference pragma.

   No_Line_Number : constant Logical_Line_Number := 0;

   --  Special value used to indicate no line number

   type Physical_Line_Number is range 1 .. Int'Last;

   for Physical_Line_Number'Size use 32;

   --  Line number type, used for storing physical line numbers (i.e. line

   --  numbers in the physical file being compiled, unaffected by the presence

   --  of source reference pragmas.

   type Column_Number is range 0 .. 32767;

   for Column_Number'Size use 16;

   --  Column number (assume that 2**15 - 1 is large enough). The range for

   --  this type is used to compute Hostparm.Max_Line_Length. See also the

   --  processing for -gnatyM in Stylesw).

   No_Column_Number : constant Column_Number := 0;

   --  Special value used to indicate no column number

   subtype Source_Buffer is Text_Buffer;

   --  Type used to store text of a source file . The buffer for the main

   --  source (the source specified on the command line) has a lower bound

   --  starting at zero. Subsequent subsidiary sources have lower bounds

   --  which are one greater than the previous upper bound.

   subtype Big_Source_Buffer is Text_Buffer (0 .. Text_Ptr'Last);

   --  This is a virtual type used as the designated type of the access type

   --  Source_Buffer_Ptr, see Osint.Read_Source_File for details.

   type Source_Buffer_Ptr is access all Big_Source_Buffer;

   for Source_Buffer_Ptr'Storage_Size use 0;

   --  Pointer to source buffer. We use virtual origin addressing for source

   --  buffers, with thin pointers. The pointer points to a virtual instance

   --  of type Big_Source_Buffer, where the actual type is in fact of type

   --  Source_Buffer. The address is adjusted so that the virtual origin

   --  addressing works correctly. See Osint.Read_Source_Buffer for further

   --  details.

   subtype Source_Ptr is Text_Ptr;

   --  Type used to represent a source location, which is a subscript of a

   --  character in the source buffer. As noted above, different source buffers

   --  have different ranges, so it is possible to tell from a Source_Ptr value

   --  which source it refers to. Note that negative numbers are allowed to

   --  accommodate the following special values.

   No_Location : constant Source_Ptr := -1;

   --  Value used to indicate no source position set in a node. A test for a

   --  Source_Ptr value being > No_Location is the approved way to test for a

   --  standard value that does not include No_Location or any of the following

   --  special definitions. One important use of No_Location is to label

   --  generated nodes that we don't want the debugger to see in normal mode

   --  (very often we conditionalize so that we set No_Location in normal mode

   --  and the corresponding source line in -gnatD mode).

   Standard_Location : constant Source_Ptr := -2;

   --  Used for all nodes in the representation of package Standard other than

   --  nodes representing the contents of Standard.ASCII. Note that testing for

   --  a value being <= Standard_Location tests for both Standard_Location and

   --  for Standard_ASCII_Location.

   Standard_ASCII_Location : constant Source_Ptr := -3;

   --  Used for all nodes in the presentation of package Standard.ASCII

   System_Location : constant Source_Ptr := -4;

   --  Used to identify locations of pragmas scanned by Targparm, where we know

   --  the location is in System, but we don't know exactly what line.

   First_Source_Ptr : constant Source_Ptr := 0;

   --  Starting source pointer index value for first source program

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

   -- Range Definitions for Tree Data --

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

   --  The tree has fields that can hold any of the following types:

   --    Pointers to other tree nodes (type Node_Id)

   --    List pointers (type List_Id)

   --    Element list pointers (type Elist_Id)

   --    Names (type Name_Id)

   --    Strings (type String_Id)

   --    Universal integers (type Uint)

   --    Universal reals (type Ureal)

   --  In most contexts, the strongly typed interface determines which of

   --  these types is present. However, there are some situations (involving

   --  untyped traversals of the tree), where it is convenient to be easily

   --  able to distinguish these values. The underlying representation in all

   --  cases is an integer type Union_Id, and we ensure that the range of

   --  the various possible values for each of the above types is disjoint

   --  so that this distinction is possible.

   type Union_Id is new Int;

   --  The type in the tree for a union of possible ID values

   --  Note: it is also helpful for debugging purposes to make these ranges

   --  distinct. If a bug leads to misidentification of a value, then it will

   --  typically result in an out of range value and a Constraint_Error.

   List_Low_Bound : constant := -100_000_000;

   --  The List_Id values are subscripts into an array of list headers which

   --  has List_Low_Bound as its lower bound. This value is chosen so that all

   --  List_Id values are negative, and the value zero is in the range of both

   --  List_Id and Node_Id values (see further description below).

   List_High_Bound : constant := 0;

   --  Maximum List_Id subscript value. This allows up to 100 million list Id

   --  values, which is in practice infinite, and there is no need to check the

   --  range. The range overlaps the node range by one element (with value

   --  zero), which is used both for the Empty node, and for indicating no

   --  list. The fact that the same value is used is convenient because it

   --  means that the default value of Empty applies to both nodes and lists,

   --  and also is more efficient to test for.

   Node_Low_Bound : constant := 0;

   --  The tree Id values start at zero, because we use zero for Empty (to

   --  allow a zero test for Empty). Actual tree node subscripts start at 0

   --  since Empty is a legitimate node value.

   Node_High_Bound : constant := 099_999_999;

   --  Maximum number of nodes that can be allocated is 100 million, which

   --  is in practice infinite, and there is no need to check the range.

   Elist_Low_Bound : constant := 100_000_000;

   --  The Elist_Id values are subscripts into an array of elist headers which

   --  has Elist_Low_Bound as its lower bound.

   Elist_High_Bound : constant := 199_999_999;

   --  Maximum Elist_Id subscript value. This allows up to 100 million Elists,

   --  which is in practice infinite and there is no need to check the range.

   Elmt_Low_Bound : constant := 200_000_000;

   --  Low bound of element Id values. The use of these values is internal to

   --  the Elists package, but the definition of the range is included here

   --  since it must be disjoint from other Id values. The Elmt_Id values are

   --  subscripts into an array of list elements which has this as lower bound.

   Elmt_High_Bound : constant := 299_999_999;

   --  Upper bound of Elmt_Id values. This allows up to 100 million element

   --  list members, which is in practice infinite (no range check needed).

   Names_Low_Bound : constant := 300_000_000;

   --  Low bound for name Id values

   Names_High_Bound : constant := 399_999_999;

   --  Maximum number of names that can be allocated is 100 million, which is

   --  in practice infinite and there is no need to check the range.

   Strings_Low_Bound : constant := 400_000_000;

   --  Low bound for string Id values

   Strings_High_Bound : constant := 499_999_999;

   --  Maximum number of strings that can be allocated is 100 million, which

   --  is in practice infinite and there is no need to check the range.

   Ureal_Low_Bound : constant := 500_000_000;

   --  Low bound for Ureal values

   Ureal_High_Bound : constant := 599_999_999;

   --  Maximum number of Ureal values stored is 100_000_000 which is in

   --  practice infinite so that no check is required.

   Uint_Low_Bound : constant := 600_000_000;

   --  Low bound for Uint values

   Uint_Table_Start : constant := 2_000_000_000;

   --  Location where table entries for universal integers start (see

   --  Uintp spec for details of the representation of Uint values).

   Uint_High_Bound : constant := 2_099_999_999;

   --  The range of Uint values is very large, since a substantial part

   --  of this range is used to store direct values, see Uintp for details.

   --  The following subtype definitions are used to provide convenient names

   --  for membership tests on Int values to see what data type range they

   --  lie in. Such tests appear only in the lowest level packages.

   subtype List_Range      is Union_Id

     range List_Low_Bound   .. List_High_Bound;

   subtype Node_Range      is Union_Id

     range Node_Low_Bound   .. Node_High_Bound;

   subtype Elist_Range     is Union_Id

     range Elist_Low_Bound  .. Elist_High_Bound;

   subtype Elmt_Range      is Union_Id

     range Elmt_Low_Bound   .. Elmt_High_Bound;

   subtype Names_Range     is Union_Id

     range Names_Low_Bound   .. Names_High_Bound;

   subtype Strings_Range   is Union_Id

     range Strings_Low_Bound .. Strings_High_Bound;

   subtype Uint_Range      is Union_Id

     range Uint_Low_Bound    .. Uint_High_Bound;

   subtype Ureal_Range     is Union_Id

     range Ureal_Low_Bound    .. Ureal_High_Bound;

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

   -- Types for Atree Package --

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

   --  Node_Id values are used to identify nodes in the tree. They are

   --  subscripts into the Node table declared in package Tree. Note that

   --  the special values Empty and Error are subscripts into this table,

   --  See package Atree for further details.

   type Node_Id is range Node_Low_Bound .. Node_High_Bound;

   --  Type used to identify nodes in the tree

   subtype Entity_Id is Node_Id;

   --  A synonym for node types, used in the entity package to refer to nodes

   --  that are entities (i.e. nodes with an Nkind of N_Defining_xxx) All such

   --  nodes are extended nodes and these are the only extended nodes, so that

   --  in practice entity and extended nodes are synonymous.

   subtype Node_Or_Entity_Id is Node_Id;

   --  A synonym for node types, used in cases where a given value may be used

   --  to represent either a node or an entity. We like to minimize such uses

   --  for obvious reasons of logical type consistency, but where such uses

   --  occur, they should be documented by use of this type.

   Empty : constant Node_Id := Node_Low_Bound;

   --  Used to indicate null node. A node is actually allocated with this

   --  Id value, so that Nkind (Empty) = N_Empty. Note that Node_Low_Bound

   --  is zero, so Empty = No_List = zero.

   Empty_List_Or_Node : constant := 0;

   --  This constant is used in situations (e.g. initializing empty fields)

   --  where the value set will be used to represent either an empty node

   --  or a non-existent list, depending on the context.

   Error : constant Node_Id := Node_Low_Bound + 1;

   --  Used to indicate that there was an error in the source program. A node

   --  is actually allocated at this address, so that Nkind (Error) = N_Error.

   Empty_Or_Error : constant Node_Id := Error;

   --  Since Empty and Error are the first two Node_Id values, the test for

   --  N <= Empty_Or_Error tests to see if N is Empty or Error. This definition

   --  provides convenient self-documentation for such tests.

   First_Node_Id  : constant Node_Id := Node_Low_Bound;

   --  Subscript of first allocated node. Note that Empty and Error are both

   --  allocated nodes, whose Nkind fields can be accessed without error.

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

   -- Types for Nlists Package --

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

   --  List_Id values are used to identify node lists in the tree. They are

   --  subscripts into the Lists table declared in package Tree. Note that the

   --  special value Error_List is a subscript in this table, but the value

   --  No_List is *not* a valid subscript, and any attempt to apply list

   --  operations to No_List will cause a (detected) error.

   type List_Id is range List_Low_Bound .. List_High_Bound;

   --  Type used to identify a node list

   No_List : constant List_Id := List_High_Bound;

   --  Used to indicate absence of a list. Note that the value is zero, which

   --  is the same as Empty, which is helpful in initializing nodes where a

   --  value of zero can represent either an empty node or an empty list.

   Error_List : constant List_Id := List_Low_Bound;

   --  Used to indicate that there was an error in the source program in a

   --  context which would normally require a list. This node appears to be

   --  an empty list to the list operations (a null list is actually allocated

   --  which has this Id value).

   First_List_Id : constant List_Id := Error_List;

   --  Subscript of first allocated list header

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

   -- Types for Elists Package --

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

   --  Element list Id values are used to identify element lists stored in the

   --  tree (see package Atree for further details). They are formed by adding

   --  a bias (Element_List_Bias) to subscript values in the same array that is

   --  used for node list headers.

   type Elist_Id is range Elist_Low_Bound .. Elist_High_Bound;

   --  Type used to identify an element list (Elist header table subscript)

   No_Elist : constant Elist_Id := Elist_Low_Bound;

   --  Used to indicate absence of an element list. Note that this is not

   --  an actual Elist header, so element list operations on this value

   --  are not valid.

   First_Elist_Id : constant Elist_Id := No_Elist + 1;

   --  Subscript of first allocated Elist header

   --  Element Id values are used to identify individual elements of an

   --  element list (see package Elists for further details).

   type Elmt_Id is range Elmt_Low_Bound .. Elmt_High_Bound;

   --  Type used to identify an element list

   No_Elmt : constant Elmt_Id := Elmt_Low_Bound;

   --  Used to represent empty element

   First_Elmt_Id : constant Elmt_Id := No_Elmt + 1;

   --  Subscript of first allocated Elmt table entry

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

   -- Types for Stringt Package --

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

   --  String_Id values are used to identify entries in the strings table. They

   --  are subscripts into the strings table defined in package Strings.

   --  Note that with only a few exceptions, which are clearly documented, the

   --  type String_Id should be regarded as a private type. In particular it is

   --  never appropriate to perform arithmetic operations using this type.

   type String_Id is range Strings_Low_Bound .. Strings_High_Bound;

   --  Type used to identify entries in the strings table

   No_String : constant String_Id := Strings_Low_Bound;

   --  Used to indicate missing string Id. Note that the value zero is used

   --  to indicate a missing data value for all the Int types in this section.

   First_String_Id : constant String_Id := No_String + 1;

   --  First subscript allocated in string table

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

   -- Character Code Type --

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

   --  The type Char is used for character data internally in the compiler, but

   --  character codes in the source are represented by the Char_Code type.

   --  Each character literal in the source is interpreted as being one of the

   --  16#8000_0000 possible Wide_Wide_Character codes, and a unique Integer

   --  Value is assigned, corresponding to the UTF_32 value, which also

   --  corresponds to the POS value in the Wide_Wide_Character type, and also

   --  corresponds to the POS value in the Wide_Character and Character types

   --  for values that are in appropriate range. String literals are similarly

   --  interpreted as a sequence of such codes.

   type Char_Code_Base is mod 2 ** 32;

   for Char_Code_Base'Size use 32;

   subtype Char_Code is Char_Code_Base range 0 .. 16#7FFF_FFFF#;

   for Char_Code'Value_Size use 32;

   for Char_Code'Object_Size use 32;

   function Get_Char_Code (C : Character) return Char_Code;

   pragma Inline (Get_Char_Code);

   --  Function to obtain internal character code from source character. For

   --  the moment, the internal character code is simply the Pos value of the

   --  input source character, but we provide this interface for possible

   --  later support of alternative character sets.

   function In_Character_Range (C : Char_Code) return Boolean;

   pragma Inline (In_Character_Range);

   --  Determines if the given character code is in range of type Character,

   --  and if so, returns True. If not, returns False.

   function In_Wide_Character_Range (C : Char_Code) return Boolean;

   pragma Inline (In_Wide_Character_Range);

   --  Determines if the given character code is in range of the type

   --  Wide_Character, and if so, returns True. If not, returns False.

   function Get_Character (C : Char_Code) return Character;

   pragma Inline (Get_Character);

   --  For a character C that is in Character range (see above function), this

   --  function returns the corresponding Character value. It is an error to

   --  call Get_Character if C is not in Character range.

   function Get_Wide_Character (C : Char_Code) return Wide_Character;

   --  For a character C that is in Wide_Character range (see above function),

   --  this function returns the corresponding Wide_Character value. It is an

   --  error to call Get_Wide_Character if C is not in Wide_Character range.

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

   -- Types used for Library Management --

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

   type Unit_Number_Type is new Int;

   --  Unit number. The main source is unit 0, and subsidiary sources have

   --  non-zero numbers starting with 1. Unit numbers are used to index the

   --  file table in Lib.

   Main_Unit : constant Unit_Number_Type := 0;

   --  Unit number value for main unit

   No_Unit : constant Unit_Number_Type := -1;

   --  Special value used to signal no unit

   type Source_File_Index is new Int range -1 .. Int'Last;

   --  Type used to index the source file table (see package Sinput)

   Internal_Source_File : constant Source_File_Index :=

                            Source_File_Index'First;

   --  Value used to indicate the buffer for the source-code-like strings

   --  internally created withing the compiler (see package Sinput)

   No_Source_File : constant Source_File_Index := 0;

   --  Value used to indicate no source file present

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

   -- Representation of Time Stamps --

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

   --  All compiled units are marked with a time stamp which is derived from

   --  the source file (we assume that the host system has the concept of a

   --  file time stamp which is modified when a file is modified). These

   --  time stamps are used to ensure consistency of the set of units that

   --  constitutes a library. Time stamps are 12 character strings with

   --  with the following format:

   --     YYYYMMDDHHMMSS

   --       YYYY   year

   --       MM     month (2 digits 01-12)

   --       DD     day (2 digits 01-31)

   --       HH     hour (2 digits 00-23)

   --       MM     minutes (2 digits 00-59)

   --       SS     seconds (2 digits 00-59)

   --  In the case of Unix systems (and other systems which keep the time in

   --  GMT), the time stamp is the GMT time of the file, not the local time.

   --  This solves problems in using libraries across networks with clients

   --  spread across multiple time-zones.

   Time_Stamp_Length : constant := 14;

   --  Length of time stamp value

   subtype Time_Stamp_Index is Natural range 1 .. Time_Stamp_Length;

   type Time_Stamp_Type is new String (Time_Stamp_Index);

   --  Type used to represent time stamp

   Empty_Time_Stamp : constant Time_Stamp_Type := (others => ' ');

   --  Value representing an empty or missing time stamp. Looks less than any

   --  real time stamp if two time stamps are compared. Note that although this

   --  is not private, clients should not rely on the exact way in which this

   --  string is represented, and instead should use the subprograms below.

   Dummy_Time_Stamp : constant Time_Stamp_Type := (others => '0');

   --  This is used for dummy time stamp values used in the D lines for

   --  non-existent files, and is intended to be an impossible value.

   function "="  (Left, Right : Time_Stamp_Type) return Boolean;

   function "<=" (Left, Right : Time_Stamp_Type) return Boolean;

   function ">=" (Left, Right : Time_Stamp_Type) return Boolean;

   function "<"  (Left, Right : Time_Stamp_Type) return Boolean;

   function ">"  (Left, Right : Time_Stamp_Type) return Boolean;

   --  Comparison functions on time stamps. Note that two time stamps are

   --  defined as being equal if they have the same day/month/year and the

   --  hour/minutes/seconds values are within 2 seconds of one another. This

   --  deals with rounding effects in library file time stamps caused by

   --  copying operations during installation. We have particularly noticed

   --  that WinNT seems susceptible to such changes.

   --

   --  Note : the Empty_Time_Stamp value looks equal to itself, and less than

   --  any non-empty time stamp value.

   procedure Split_Time_Stamp

     (TS      : Time_Stamp_Type;

      Year    : out Nat;

      Month   : out Nat;

      Day     : out Nat;

      Hour    : out Nat;

      Minutes : out Nat;

      Seconds : out Nat);

   --  Given a time stamp, decompose it into its components

   procedure Make_Time_Stamp

     (Year    : Nat;

      Month   : Nat;

      Day     : Nat;

      Hour    : Nat;

      Minutes : Nat;

      Seconds : Nat;

      TS      : out Time_Stamp_Type);

   --  Given the components of a time stamp, initialize the value

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

   -- Types used for Pragma Suppress Management --

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

   type Check_Id is new Nat;

   --  Type used to represent a check id

   No_Check_Id         : constant := 0;

   --  Check_Id value used to indicate no check

   Access_Check        : constant :=  1;

   Accessibility_Check : constant :=  2;

   Alignment_Check     : constant :=  3;

   Discriminant_Check  : constant :=  4;

   Division_Check      : constant :=  5;

   Elaboration_Check   : constant :=  6;

   Index_Check         : constant :=  7;

   Length_Check        : constant :=  8;

   Overflow_Check      : constant :=  9;

   Range_Check         : constant := 10;

   Storage_Check       : constant := 11;

   Tag_Check           : constant := 12;

   Validity_Check      : constant := 13;

   --  Values used to represent individual predefined checks

   All_Checks          : constant := 14;

   --  Value used to represent All_Checks value

   subtype Predefined_Check_Id is Check_Id range 1 .. All_Checks;

   --  Subtype for predefined checks, including All_Checks

   --  The following array contains an entry for each recognized check name

   --  for pragma Suppress. It is used to represent current settings of scope

   --  based suppress actions from pragma Suppress or command line settings.

   --  Note: when Suppress_Array (All_Checks) is True, then generally all other

   --  specific check entries are set True, except for the Elaboration_Check

   --  entry which is set only if an explicit Suppress for this check is given.

   --  The reason for this non-uniformity is that we do not want All_Checks to

   --  suppress elaboration checking when using the static elaboration model.

   --  We recognize only an explicit suppress of Elaboration_Check as a signal

   --  that the static elaboration checking should skip a compile time check.

   type Suppress_Array is array (Predefined_Check_Id) of Boolean;

   pragma Pack (Suppress_Array);

   --  To add a new check type to GNAT, the following steps are required:

   --    1.  Add an entry to Snames spec and body for the new name

   --    2.  Add an entry to the definition of Check_Id above

   --    3.  Add a new function to Checks to handle the new check test

   --    4.  Add a new Do_xxx_Check flag to Sinfo (if required)

   --    5.  Add appropriate checks for the new test

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

   -- Global Exception Declarations --

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

   --  This section contains declarations of exceptions that are used

   --  throughout the compiler or in other GNAT tools.

   Unrecoverable_Error : exception;

   --  This exception is raised to immediately terminate the compilation of the

   --  current source program. Used in situations where things are bad enough

   --  that it doesn't seem worth continuing (e.g. max errors reached, or a

   --  required file is not found). Also raised when the compiler finds itself

   --  in trouble after an error (see Comperr).

   Terminate_Program : exception;

   --  This exception is raised to immediately terminate the tool being

   --  executed. Each tool where this exception may be raised must have a

   --  single exception handler that contains only a null statement and that is

   --  the last statement of the program. If needed, procedure Set_Exit_Status

   --  is called with the appropriate exit status before raising

   --  Terminate_Program.

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

   -- Parameter Mechanism Control --

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

   --  Function and parameter entities have a field that records the

   --  passing mechanism. See specification of Sem_Mech for full details.

   --  The following subtype is used to represent values of this type:

   subtype Mechanism_Type is Int range -18 .. Int'Last;

   --  Type used to represent a mechanism value. This is a subtype rather

   --  than a type to avoid some annoying processing problems with certain

   --  routines in Einfo (processing them to create the corresponding C).

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

   -- Run-Time Exception Codes --

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

   --  When the code generator generates a run-time exception, it provides a

   --  reason code which is one of the following. This reason code is used to

   --  select the appropriate run-time routine to be called, determining both

   --  the exception to be raised, and the message text to be added.

   --  The prefix CE/PE/SE indicates the exception to be raised

   --    CE = Constraint_Error

   --    PE = Program_Error

   --    SE = Storage_Error

   --  The remaining part of the name indicates the message text to be added,

   --  where all letters are lower case, and underscores are converted to

   --  spaces (for example CE_Invalid_Data adds the text "invalid data").

   --  To add a new code, you need to do the following:

   --    1. Modify the type and subtype declarations below appropriately,

   --       keeping things in alphabetical order.

   --    2. Modify the corresponding definitions in types.h, including

   --       the definition of last_reason_code.

   --    3. Add a new routine in Ada.Exceptions with the appropriate call

   --       and static string constant. Note that there is more than one

   --       version of a-except.adb which must be modified.

   type RT_Exception_Code is

     (CE_Access_Check_Failed,            -- 00

      CE_Access_Parameter_Is_Null,       -- 01

      CE_Discriminant_Check_Failed,      -- 02

      CE_Divide_By_Zero,                 -- 03

      CE_Explicit_Raise,                 -- 04

      CE_Index_Check_Failed,             -- 05

      CE_Invalid_Data,                   -- 06

      CE_Length_Check_Failed,            -- 07

      CE_Null_Exception_Id,              -- 08

      CE_Null_Not_Allowed,               -- 09

      CE_Overflow_Check_Failed,          -- 10

      CE_Partition_Check_Failed,         -- 11

      CE_Range_Check_Failed,             -- 12

      CE_Tag_Check_Failed,               -- 13

      PE_Access_Before_Elaboration,      -- 14

      PE_Accessibility_Check_Failed,     -- 15

      PE_Address_Of_Intrinsic,           -- 16

      PE_All_Guards_Closed,              -- 17

      PE_Current_Task_In_Entry_Body,     -- 18

      PE_Duplicated_Entry_Address,       -- 19

      PE_Explicit_Raise,                 -- 20

      PE_Finalize_Raised_Exception,      -- 21

      PE_Implicit_Return,                -- 22

      PE_Misaligned_Address_Value,       -- 23

      PE_Missing_Return,                 -- 24

      PE_Overlaid_Controlled_Object,     -- 25

      PE_Potentially_Blocking_Operation, -- 26

      PE_Stubbed_Subprogram_Called,      -- 27

      PE_Unchecked_Union_Restriction,    -- 28

      PE_Non_Transportable_Actual,       -- 29