gcc/ada/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) 2000-2005, 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 2,  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.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, USA.                                              --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNAT was originally developed  by the GNAT team at  New York University. --
  30 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 --  This package provides an interface for raising predefined exceptions
  35 --  with an exception message. It can be used from Pure units.
  36
  37 --  There is no prohibition in Ada that prevents exceptions being raised
  38 --  from within pure units. The raise statement is perfectly acceptable.
  39
  40 --  However, it is not normally possible to raise an exception with a
  41 --  message because the routine Ada.Exceptions.Raise_Exception is not in
  42 --  a Pure unit. This is an annoying and unnecessary restrictiona and this
  43 --  package allows for raising the standard predefined exceptions at least.
  44
  45 package GNAT.Exceptions is
  46    pragma Pure;
  47
  48    type Exception_Type is limited null record;
  49    --  Type used to specify which exception to raise
  50
  51    --  Really Exception_Type is Exception_Id, but Exception_Id can't be
  52    --  used directly since it is declared in the non-pure unit Ada.Exceptions,
  53
  54    --  Exception_Id is in fact simply a pointer to the type Exception_Data
  55    --  declared in System.Standard_Library (which is also non-pure). So what
  56    --  we do is to define it here as a by reference type (any by reference
  57    --  type would do), and then Import the definitions from Standard_Library.
  58    --  Since this is a by reference type, these will be passed by reference,
  59    --  which has the same effect as passing a pointer.
  60
  61    --  This type is not private because keeping it by reference would require
  62    --  defining it in a way (e.g a tagged type) that would drag other run time
  63    --  files, which is unwanted in the case of e.g ravenscar where we want to
  64    --  minimize the number of run time files needed by default.
  65
  66    CE : constant Exception_Type;  -- Constraint_Error
  67    PE : constant Exception_Type;  -- Program_Error
  68    SE : constant Exception_Type;  -- Storage_Error
  69    TE : constant Exception_Type;  -- Tasking_Error
  70    --  One of these constants is used in the call to specify the exception
  71
  72    procedure Raise_Exception (E : Exception_Type; Message : String);
  73    pragma Import (Ada, Raise_Exception, "__gnat_raise_exception");
  74    pragma No_Return (Raise_Exception);
  75    --  Raise specified exception with specified message
  76
  77 private
  78    pragma Import (C, CE, "constraint_error");
  79    pragma Import (C, PE, "program_error");
  80    pragma Import (C, SE, "storage_error");
  81    pragma Import (C, TE, "tasking_error");
  82    --  References to the exception structures in the standard library
  83
  84 end GNAT.Exceptions;