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------------------------------------------------------------------------------
--                                                                          --
--                         GNAT COMPILER COMPONENTS                         --
--                                                                          --
--              S Y S T E M . S T A N D A R D _ L I B R A R Y               --
--                                                                          --
--                                 S p e c                                  --
--                                                                          --
--          Copyright (C) 1992-2020, 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 is included in all programs. It contains declarations that
--  are required to be part of every Ada program. A special mechanism is
--  required to ensure that these are loaded, since it may be the case in
--  some programs that the only references to these required packages are
--  from C code or from code generated directly by Gigi, and in both cases
--  the binder is not aware of such references.

--  System.Standard_Library also includes data that must be present in every
--  program, in particular data for all the standard exceptions, and also some
--  subprograms that must be present in every program.

--  The binder unconditionally includes s-stalib.ali, which ensures that this
--  package and the packages it references are included in all Ada programs,
--  together with the included data.

pragma Compiler_Unit_Warning;

pragma Polling (Off);
--  We must turn polling off for this unit, because otherwise we get
--  elaboration circularities with Ada.Exceptions if polling is on.

with Ada.Unchecked_Conversion;

package System.Standard_Library is

   --  Historical note: pragma Preelaborate was surrounded by a pair of pragma
   --  Warnings (Off/On) to circumvent a bootstrap issue.

   pragma Preelaborate;

   subtype Big_String is String (1 .. Positive'Last);
   pragma Suppress_Initialization (Big_String);
   --  Type used to obtain string access to given address. Initialization is
   --  suppressed, since we never want to have variables of this type, and
   --  we never want to attempt initialiazation of virtual variables of this
   --  type (e.g. when pragma Normalize_Scalars is used).

   type Big_String_Ptr is access all Big_String;
   for Big_String_Ptr'Storage_Size use 0;
   --  We use this access type to pass a pointer to an area of storage to be
   --  accessed as a string. Of course when this pointer is used, it is the
   --  responsibility of the accessor to ensure proper bounds. The storage
   --  size clause ensures we do not allocate variables of this type.

   function To_Ptr is
     new Ada.Unchecked_Conversion (System.Address, Big_String_Ptr);

   -------------------------------------
   -- Exception Declarations and Data --
   -------------------------------------

   type Raise_Action is access procedure;
   --  A pointer to a procedure used in the Raise_Hook field

   type Exception_Data;
   type Exception_Data_Ptr is access all Exception_Data;
   --  An equivalent of Exception_Id that is public

   --  The following record defines the underlying representation of exceptions

   --  WARNING: Any changes to this may need to be reflected in the following
   --  locations in the compiler and runtime code:

   --    1. The Internal_Exception routine in s-exctab.adb
   --    2. The processing in gigi that tests Not_Handled_By_Others
   --    3. Expand_N_Exception_Declaration in Exp_Ch11
   --    4. The construction of the exception type in Cstand

   type Exception_Data is record
      Not_Handled_By_Others : Boolean;
      --  Normally set False, indicating that the exception is handled in the
      --  usual way by others (i.e. an others handler handles the exception).
      --  Set True to indicate that this exception is not caught by others
      --  handlers, but must be explicitly named in a handler. This latter
      --  setting is currently used by the Abort_Signal.

      Lang : Character;
      --  A character indicating the language raising the exception.
      --  Set to "A" for exceptions defined by an Ada program.
      --  Set to "C" for imported C++ exceptions.

      Name_Length : Natural;
      --  Length of fully expanded name of exception

      Full_Name : System.Address;
      --  Fully expanded name of exception, null terminated
      --  You can use To_Ptr to convert this to a string.

      HTable_Ptr : Exception_Data_Ptr;
      --  Hash table pointer used to link entries together in the hash table
      --  built (by Register_Exception in s-exctab.adb) for converting between
      --  identities and names.

      Foreign_Data : Address;
      --  Data for imported exceptions. Not used in the Ada case. This
      --  represents the address of the RTTI for the C++ case.

      Raise_Hook : Raise_Action;
      --  This field can be used to place a "hook" on an exception. If the
      --  value is non-null, then it points to a procedure which is called
      --  whenever the exception is raised. This call occurs immediately,
      --  before any other actions taken by the raise (and in particular
      --  before any unwinding of the stack occurs).
   end record;

   --  Definitions for standard predefined exceptions defined in Standard,

   --  Why are the NULs necessary here, seems like they should not be
   --  required, since Gigi is supposed to add a Nul to each name ???

   Constraint_Error_Name : constant String := "CONSTRAINT_ERROR" & ASCII.NUL;
   Program_Error_Name    : constant String := "PROGRAM_ERROR"    & ASCII.NUL;
   Storage_Error_Name    : constant String := "STORAGE_ERROR"    & ASCII.NUL;
   Tasking_Error_Name    : constant String := "TASKING_ERROR"    & ASCII.NUL;
   Abort_Signal_Name     : constant String := "_ABORT_SIGNAL"    & ASCII.NUL;

   Numeric_Error_Name    : constant String := "NUMERIC_ERROR"    & ASCII.NUL;
   --  This is used only in the Ada 83 case, but it is not worth having a
   --  separate version of s-stalib.ads for use in Ada 83 mode.

   Constraint_Error_Def : aliased Exception_Data :=
     (Not_Handled_By_Others => False,
      Lang                  => 'A',
      Name_Length           => Constraint_Error_Name'Length,
      Full_Name             => Constraint_Error_Name'Address,
      HTable_Ptr            => null,
      Foreign_Data          => Null_Address,
      Raise_Hook            => null);

   Numeric_Error_Def : aliased Exception_Data :=
     (Not_Handled_By_Others => False,
      Lang                  => 'A',
      Name_Length           => Numeric_Error_Name'Length,
      Full_Name             => Numeric_Error_Name'Address,
      HTable_Ptr            => null,
      Foreign_Data          => Null_Address,
      Raise_Hook            => null);

   Program_Error_Def : aliased Exception_Data :=
     (Not_Handled_By_Others => False,
      Lang                  => 'A',
      Name_Length           => Program_Error_Name'Length,
      Full_Name             => Program_Error_Name'Address,
      HTable_Ptr            => null,
      Foreign_Data          => Null_Address,
      Raise_Hook            => null);

   Storage_Error_Def : aliased Exception_Data :=
     (Not_Handled_By_Others => False,
      Lang                  => 'A',
      Name_Length           => Storage_Error_Name'Length,
      Full_Name             => Storage_Error_Name'Address,
      HTable_Ptr            => null,
      Foreign_Data          => Null_Address,
      Raise_Hook            => null);

   Tasking_Error_Def : aliased Exception_Data :=
     (Not_Handled_By_Others => False,
      Lang                  => 'A',
      Name_Length           => Tasking_Error_Name'Length,
      Full_Name             => Tasking_Error_Name'Address,
      HTable_Ptr            => null,
      Foreign_Data          => Null_Address,
      Raise_Hook            => null);

   Abort_Signal_Def : aliased Exception_Data :=
     (Not_Handled_By_Others => True,
      Lang                  => 'A',
      Name_Length           => Abort_Signal_Name'Length,
      Full_Name             => Abort_Signal_Name'Address,
      HTable_Ptr            => null,
      Foreign_Data          => Null_Address,
      Raise_Hook            => null);

   pragma Export (C, Constraint_Error_Def, "constraint_error");
   pragma Export (C, Numeric_Error_Def,    "numeric_error");
   pragma Export (C, Program_Error_Def,    "program_error");
   pragma Export (C, Storage_Error_Def,    "storage_error");
   pragma Export (C, Tasking_Error_Def,    "tasking_error");
   pragma Export (C, Abort_Signal_Def,     "_abort_signal");

   Local_Partition_ID : Natural := 0;
   --  This variable contains the local Partition_ID that will be used when
   --  building exception occurrences. In distributed mode, it will be
   --  set by each partition to the correct value during the elaboration.

   type Exception_Trace_Kind is
     (RM_Convention,
      --  No particular trace is requested, only unhandled exceptions
      --  in the environment task (following the RM) will be printed.
      --  This is the default behavior.

      Every_Raise,
      --  Denotes the initial raise event for any exception occurrence, either
      --  explicit or due to a specific language rule, within the context of a
      --  task or not.

      Unhandled_Raise,
      --  Denotes the raise events corresponding to exceptions for which there
      --  is no user defined handler. This includes unhandled exceptions in
      --  task bodies.

      Unhandled_Raise_In_Main
      --  Same as Unhandled_Raise, except exceptions in task bodies are not
      --  included. Same as RM_Convention, except (1) the message is printed as
      --  soon as the environment task completes due to an unhandled exception
      --  (before awaiting the termination of dependent tasks, and before
      --  library-level finalization), and (2) a symbolic traceback is given
      --  if possible. This is the default behavior if the binder switch -E is
      --  used.
     );
   --  Provide a way to denote different kinds of automatic traces related
   --  to exceptions that can be requested.

   Exception_Trace : Exception_Trace_Kind := RM_Convention;
   pragma Atomic (Exception_Trace);
   --  By default, follow the RM convention

   -----------------
   -- Subprograms --
   -----------------

   procedure Abort_Undefer_Direct;
   pragma Inline (Abort_Undefer_Direct);
   --  A little procedure that just calls Abort_Undefer.all, for use in
   --  clean up procedures, which only permit a simple subprogram name.

   procedure Adafinal;
   --  Performs the Ada Runtime finalization the first time it is invoked.
   --  All subsequent calls are ignored.

end System.Standard_Library;