------------------------------------------------------------------------------
--                                                                          --
--                         GNAT LIBRARY COMPONENTS                          --
--                                                                          --
--               G N A T . C U R R E N T _ E X C E P T I O N                --
--                                                                          --
--                                 S p e c                                  --
--                                                                          --
--         Copyright (C) 1996-2000 Ada Core Technologies, 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 2,  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 COPYING.  If not, write --
-- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
-- MA 02111-1307, USA.                                                      --
--                                                                          --
-- 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.      --
--                                                                          --
------------------------------------------------------------------------------

--  This package provides routines for obtaining the current exception
--  information in Ada 83 style. In Ada 83, there was no official method
--  for obtaining exception information, but a number of vendors supplied
--  routines for this purpose, and this package closely approximates the
--  interfaces supplied by DEC Ada 83 and VADS Ada.

--  The routines in this package are associated with a particular exception
--  handler, and can only be called from within an exception handler. See
--  also the package GNAT.Most_Recent_Exception, which provides access to
--  the most recently raised exception, and is not limited to static calls
--  from an exception handler.

package GNAT.Current_Exception is
pragma Pure (Current_Exception);

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

   function Exception_Information return String;
   --  Returns the result of calling Ada.Exceptions.Exception_Information
   --  with an argument that is the Exception_Occurrence corresponding to
   --  the current exception. Returns the null string if called from outside
   --  an exception handler.

   function Exception_Message return String;
   --  Returns the result of calling Ada.Exceptions.Exception_Message with
   --  an argument that is the Exception_Occurrence corresponding to the
   --  current exception. Returns the null string if called from outside an
   --  exception handler.

   function Exception_Name return String;
   --  Returns the result of calling Ada.Exceptions.Exception_Name with
   --  an argument that is the Exception_Occurrence corresponding to the
   --  current exception. Returns the null string if called from outside
   --  an exception handler.

   --  Note: all these functions return useful information only if
   --  called statically from within an exception handler, and they
   --  return information about the exception corresponding to the
   --  handler in which they appear. This is NOT the same as the most
   --  recently raised exception. Consider the example:

   --     exception
   --        when Constraint_Error =>
   --          begin
   --             ...
   --          exception
   --             when Tasking_Error => ...
   --          end;
   --
   --          -- Exception_xxx at this point returns the information about
   --          -- the constraint error, not about any exception raised within
   --          -- the nested block since it is the static nesting that counts.

   -----------------------------------
   -- Use of Library Level Renaming --
   -----------------------------------

   --  For greater compatibility with existing legacy software, library
   --  level renaming may be used to create a function with a name matching
   --  one that is in use. For example, some versions of VADS Ada provided
   --  a functin called Current_Exception whose semantics was identical to
   --  that of GNAT. The following library level renaming declaration:

   --    with GNAT.Current_Exception;
   --    function Current_Exception
   --      renames GNAT.Current_Exception.Exception_Name;

   --  placed in a file called current_exception.ads and compiled into the
   --  application compilation environment, will make the function available
   --  in a manner exactly compatible with that in VADS Ada 83.

private
   pragma Import (Intrinsic, Exception_Information);
   pragma Import (intrinsic, Exception_Message);
   pragma Import (Intrinsic, Exception_Name);

end GNAT.Current_Exception;
