gcc/ada/s-stchop.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
   4 --                                                                          --
   5 --     S Y S T E M . S T A C K _ C H E C K I N G . O P E R A T I O N S      --
   6 --                                                                          --
   7 --                                  S p e c                                 --
   8 --                                                                          --
   9 --          Copyright (C) 1999-2007, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNARL 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. GNARL 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 GNARL; 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 -- GNARL was developed by the GNARL team at Florida State University.       --
  30 -- Extensive contributions were provided by Ada Core Technologies, Inc.     --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 --  This package provides a implementation of stack checking operations using
  35 --  comparison with stack base and limit.
  36
  37 pragma Restrictions (No_Elaboration_Code);
  38 --  We want to guarantee the absence of elaboration code because the binder
  39 --  does not handle references to this package.
  40
  41 pragma Polling (Off);
  42 --  Turn off polling, we do not want polling to take place during stack
  43 --  checking operations. It causes infinite loops and other problems.
  44
  45 with System.Storage_Elements;
  46
  47 package System.Stack_Checking.Operations is
  48    pragma Preelaborate;
  49
  50    procedure Update_Stack_Cache (Stack : Stack_Access);
  51    --  Set the stack cache for the current task. Note that this is only for
  52    --  optimization purposes, nothing can be assumed about the contents of the
  53    --  cache at any time, see Set_Stack_Info.
  54    --
  55    --  The stack cache should contain the bounds of the current task.  But
  56    --  because the RTS is not aware of task switches, the stack cache may be
  57    --  incorrect.  So when the stack pointer is not within the bounds of the
  58    --  stack cache, Stack_Check first update the cache (which is a costly
  59    --  operation hence the need of a cache).
  60
  61    procedure Invalidate_Stack_Cache (Any_Stack : Stack_Access);
  62    --  Invalidate cache entries for the task T that owns Any_Stack. This causes
  63    --  the Set_Stack_Info function to be called during the next stack check
  64    --  done by T. This can be used to interrupt task T asynchronously.
  65    --  Stack_Check should be called in loops for this to work reliably.
  66
  67    function Stack_Check (Stack_Address : System.Address) return Stack_Access;
  68    --  This version of Stack_Check should not be inlined
  69
  70    procedure Notify_Stack_Attributes
  71      (Initial_SP : System.Address;
  72       Size       : System.Storage_Elements.Storage_Offset);
  73    --  Register Initial_SP as the initial stack pointer value for the current
  74    --  task when it starts and Size as the associated stack area size. This
  75    --  should be called once, after the soft-links have been initialized and
  76    --  prior to the first "Stack_Check" call.
  77
  78 private
  79    Cache : aliased Stack_Access := Null_Stack;
  80
  81    pragma Export (C, Cache, "_gnat_stack_cache");
  82    pragma Export (C, Stack_Check, "_gnat_stack_check");
  83
  84 end System.Stack_Checking.Operations;