1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT RUN-TIME COMPONENTS                         --
4--                                                                          --
5--                      G N A T . E X C E P T I O N S                       --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--                     Copyright (C) 2000-2018, 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 an interface for raising predefined exceptions
33--  with an exception message. It can be used from Pure units.
34
35--  There is no prohibition in Ada that prevents exceptions being raised
36--  from within pure units. The raise statement is perfectly acceptable.
37
38--  However, it is not normally possible to raise an exception with a
39--  message because the routine Ada.Exceptions.Raise_Exception is not in
40--  a Pure unit. This is an annoying and unnecessary restriction and this
41--  package allows for raising the standard predefined exceptions at least.
42
43package GNAT.Exceptions is
44   pragma Pure;
45
46   type Exception_Type is limited null record;
47   --  Type used to specify which exception to raise
48
49   --  Really Exception_Type is Exception_Id, but Exception_Id can't be
50   --  used directly since it is declared in the non-pure unit Ada.Exceptions,
51
52   --  Exception_Id is in fact simply a pointer to the type Exception_Data
53   --  declared in System.Standard_Library (which is also non-pure). So what
54   --  we do is to define it here as a by reference type (any by reference
55   --  type would do), and then Import the definitions from Standard_Library.
56   --  Since this is a by reference type, these will be passed by reference,
57   --  which has the same effect as passing a pointer.
58
59   --  This type is not private because keeping it by reference would require
60   --  defining it in a way (e.g. using a tagged type) that would drag in other
61   --  run-time files, which is unwanted in the case of e.g. Ravenscar where we
62   --  want to minimize the number of run-time files needed by default.
63
64   CE : constant Exception_Type;  -- Constraint_Error
65   PE : constant Exception_Type;  -- Program_Error
66   SE : constant Exception_Type;  -- Storage_Error
67   TE : constant Exception_Type;  -- Tasking_Error
68   --  One of these constants is used in the call to specify the exception
69
70   procedure Raise_Exception (E : Exception_Type; Message : String);
71   pragma Import (Ada, Raise_Exception, "__gnat_raise_exception");
72   pragma No_Return (Raise_Exception);
73   --  Raise specified exception with specified message
74
75private
76   pragma Import (C, CE, "constraint_error");
77   pragma Import (C, PE, "program_error");
78   pragma Import (C, SE, "storage_error");
79   pragma Import (C, TE, "tasking_error");
80   --  References to the exception structures in the standard library
81
82end GNAT.Exceptions;
83