gcc/ada/libgnat/g-except.ads

   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
  43 package 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
  75 private
  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
  82 end GNAT.Exceptions;