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g-except.ads
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g-except.ads
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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- G N A T . E X C E P T I O N S --
-- --
-- S p e c --
-- --
-- Copyright (C) 2000-2008, AdaCore --
-- --
-- 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, 51 Franklin Street, Fifth Floor, --
-- Boston, MA 02110-1301, 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 an interface for raising predefined exceptions
-- with an exception message. It can be used from Pure units.
-- There is no prohibition in Ada that prevents exceptions being raised
-- from within pure units. The raise statement is perfectly acceptable.
-- However, it is not normally possible to raise an exception with a
-- message because the routine Ada.Exceptions.Raise_Exception is not in
-- a Pure unit. This is an annoying and unnecessary restriction and this
-- package allows for raising the standard predefined exceptions at least.
package GNAT.Exceptions is
pragma Pure;
type Exception_Type is limited null record;
-- Type used to specify which exception to raise
-- Really Exception_Type is Exception_Id, but Exception_Id can't be
-- used directly since it is declared in the non-pure unit Ada.Exceptions,
-- Exception_Id is in fact simply a pointer to the type Exception_Data
-- declared in System.Standard_Library (which is also non-pure). So what
-- we do is to define it here as a by reference type (any by reference
-- type would do), and then Import the definitions from Standard_Library.
-- Since this is a by reference type, these will be passed by reference,
-- which has the same effect as passing a pointer.
-- This type is not private because keeping it by reference would require
-- defining it in a way (e.g a tagged type) that would drag other run time
-- files, which is unwanted in the case of e.g ravenscar where we want to
-- minimize the number of run time files needed by default.
CE : constant Exception_Type; -- Constraint_Error
PE : constant Exception_Type; -- Program_Error
SE : constant Exception_Type; -- Storage_Error
TE : constant Exception_Type; -- Tasking_Error
-- One of these constants is used in the call to specify the exception
procedure Raise_Exception (E : Exception_Type; Message : String);
pragma Import (Ada, Raise_Exception, "__gnat_raise_exception");
pragma No_Return (Raise_Exception);
-- Raise specified exception with specified message
private
pragma Import (C, CE, "constraint_error");
pragma Import (C, PE, "program_error");
pragma Import (C, SE, "storage_error");
pragma Import (C, TE, "tasking_error");
-- References to the exception structures in the standard library
end GNAT.Exceptions;