1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT LIBRARY COMPONENTS                          --
4--                                                                          --
5--               G N A T . C U R R E N T _ E X C E P T I O N                --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--                      Copyright (C) 1996-2010, AdaCore                    --
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.                                     --
17--                                                                          --
18-- As a special exception under Section 7 of GPL version 3, you are granted --
19-- additional permissions described in the GCC Runtime Library Exception,   --
20-- version 3.1, as published by the Free Software Foundation.               --
21--                                                                          --
22-- You should have received a copy of the GNU General Public License and    --
23-- a copy of the GCC Runtime Library Exception along with this program;     --
24-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
25-- <http://www.gnu.org/licenses/>.                                          --
26--                                                                          --
27-- GNAT was originally developed  by the GNAT team at  New York University. --
28-- Extensive contributions were provided by Ada Core Technologies Inc.      --
29--                                                                          --
30------------------------------------------------------------------------------
31
32--  This package provides routines for obtaining the current exception
33--  information in Ada 83 style. In Ada 83, there was no official method
34--  for obtaining exception information, but a number of vendors supplied
35--  routines for this purpose, and this package closely approximates the
36--  interfaces supplied by DEC Ada 83 and VADS Ada.
37
38--  The routines in this package are associated with a particular exception
39--  handler, and can only be called from within an exception handler. See
40--  also the package GNAT.Most_Recent_Exception, which provides access to
41--  the most recently raised exception, and is not limited to static calls
42--  from an exception handler.
43
44package GNAT.Current_Exception is
45   pragma Pure;
46
47   -----------------
48   -- Subprograms --
49   -----------------
50
51   --  Note: the lower bound of returned String values is always one
52
53   function Exception_Information return String;
54   --  Returns the result of calling Ada.Exceptions.Exception_Information
55   --  with an argument that is the Exception_Occurrence corresponding to
56   --  the current exception. Returns the null string if called from outside
57   --  an exception handler.
58
59   function Exception_Message return String;
60   --  Returns the result of calling Ada.Exceptions.Exception_Message with
61   --  an argument that is the Exception_Occurrence corresponding to the
62   --  current exception. Returns the null string if called from outside an
63   --  exception handler.
64
65   function Exception_Name return String;
66   --  Returns the result of calling Ada.Exceptions.Exception_Name with
67   --  an argument that is the Exception_Occurrence corresponding to the
68   --  current exception. Returns the null string if called from outside
69   --  an exception handler.
70
71   --  Note: all these functions return useful information only if
72   --  called statically from within an exception handler, and they
73   --  return information about the exception corresponding to the
74   --  handler in which they appear. This is NOT the same as the most
75   --  recently raised exception. Consider the example:
76
77   --     exception
78   --        when Constraint_Error =>
79   --          begin
80   --             ...
81   --          exception
82   --             when Tasking_Error => ...
83   --          end;
84   --
85   --          -- Exception_xxx at this point returns the information about
86   --          -- the constraint error, not about any exception raised within
87   --          -- the nested block since it is the static nesting that counts.
88
89   -----------------------------------
90   -- Use of Library Level Renaming --
91   -----------------------------------
92
93   --  For greater compatibility with existing legacy software, library
94   --  level renaming may be used to create a function with a name matching
95   --  one that is in use. For example, some versions of VADS Ada provided
96   --  a function called Current_Exception whose semantics was identical to
97   --  that of GNAT. The following library level renaming declaration:
98
99   --    with GNAT.Current_Exception;
100   --    function Current_Exception
101   --      renames GNAT.Current_Exception.Exception_Name;
102
103   --  placed in a file called current_exception.ads and compiled into the
104   --  application compilation environment, will make the function available
105   --  in a manner exactly compatible with that in VADS Ada 83.
106
107private
108   pragma Import (Intrinsic, Exception_Information);
109   pragma Import (intrinsic, Exception_Message);
110   pragma Import (Intrinsic, Exception_Name);
111
112end GNAT.Current_Exception;
113