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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
-- --
-- S Y S T E M . S T A C K _ C H E C K I N G --
-- --
-- S p e c --
-- --
-- Copyright (C) 1999-2021, Free Software Foundation, Inc. --
-- --
-- GNARL 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 3, 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. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNARL was developed by the GNARL team at Florida State University. --
-- Extensive contributions were provided by Ada Core Technologies, Inc. --
-- --
------------------------------------------------------------------------------
-- This package provides a system-independent implementation of stack
-- checking using comparison with stack base and limit.
-- This package defines basic types and objects. Operations related to
-- stack checking can be found in package System.Stack_Checking.Operations.
with System.Storage_Elements;
package System.Stack_Checking is
pragma Preelaborate;
pragma Elaborate_Body;
-- This unit has a junk null body. The reason is that historically we
-- used to have a real body, and it causes bootstrapping path problems
-- to eliminate it, since the old body may still be present in the
-- compilation environment for a build.
type Stack_Info is record
Limit : System.Address := System.Null_Address;
Base : System.Address := System.Null_Address;
Size : System.Storage_Elements.Storage_Offset := 0;
end record;
-- This record may be part of a larger data structure like the
-- task control block in the tasking case.
-- This specific layout has the advantage of being compatible with the
-- Intel x86 BOUNDS instruction.
type Stack_Access is access all Stack_Info;
-- Unique local storage associated with a specific task. This storage is
-- used for the stack base and limit, and is returned by Checked_Self.
-- Only self may write this information, it may be read by any task.
-- At no time the address range Limit .. Base (or Base .. Limit for
-- upgrowing stack) may contain any address that is part of another stack.
-- The Stack_Access may be part of a larger data structure.
Multi_Processor : constant Boolean := False; -- Not supported yet
private
Null_Stack_Info : aliased Stack_Info :=
(Limit => System.Null_Address,
Base => System.Null_Address,
Size => 0);
-- Use explicit assignment to avoid elaboration code (call to init proc)
Null_Stack : constant Stack_Access := Null_Stack_Info'Access;
-- Stack_Access value that will return a Stack_Base and Stack_Limit
-- that fail any stack check.
end System.Stack_Checking;
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