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   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                      SYSTEM.MACHINE_STATE_OPERATIONS                     --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1999-2005 Free Software Foundation, Inc.          --
  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 pragma Polling (Off);
  35 --  We must turn polling off for this unit, because otherwise we get
  36 --  elaboration circularities with System.Exception_Tables.
  37
  38 with System.Storage_Elements;
  39
  40 package System.Machine_State_Operations is
  41
  42    subtype Code_Loc is System.Address;
  43    --  Code location used in building exception tables and for call
  44    --  addresses when propagating an exception (also traceback table)
  45    --  Values of this type are created by using Label'Address or
  46    --  extracted from machine states using Get_Code_Loc.
  47
  48    type Machine_State is new System.Address;
  49    --  The table based exception handling approach (see a-except.adb) isolates
  50    --  the target dependent aspects using an abstract data type interface
  51    --  to the type Machine_State, which is represented as a System.Address
  52    --  value (presumably implemented as a pointer to an appropriate record
  53    --  structure).
  54
  55    function Machine_State_Length return System.Storage_Elements.Storage_Offset;
  56    --  Function to determine the length of the Storage_Array needed to hold
  57    --  a machine state. The machine state will always be maximally aligned.
  58    --  The value returned is a constant that will be used to allocate space
  59    --  for a machine state value.
  60
  61    function Allocate_Machine_State return Machine_State;
  62    --  Allocate the required space for a Machine_State
  63
  64    procedure Free_Machine_State (M : in out Machine_State);
  65    --  Free the dynamic memory taken by Machine_State
  66
  67    --  The initial value of type Machine_State is created by the low level
  68    --  routine that actually raises an exception using the special builtin
  69    --  _builtin_machine_state. This value will typically encode the value
  70    --  of the program counter, and relevant registers. The following
  71    --  operations are defined on Machine_State values:
  72
  73    function Get_Code_Loc (M : Machine_State) return Code_Loc;
  74    --  This function extracts the program counter value from a machine
  75    --  state, which the caller uses for searching the exception tables,
  76    --  and also for recording entries in the traceback table. The call
  77    --  returns a value of Null_Loc if the machine state represents the
  78    --  outer level, or some other frame for which no information can be
  79    --  provided.
  80
  81    procedure Pop_Frame (M : Machine_State);
  82    --  This procedure pops the machine state M so that it represents the
  83    --  call point, as though the current subprogram had returned. It
  84    --  changes only the value referenced by M, and does not affect
  85    --  the current stack environment.
  86
  87    function Fetch_Code (Loc : Code_Loc) return Code_Loc;
  88    --  Some architectures (notably VMS) use a descriptor to describe
  89    --  a subprogram address. This function computes the actual starting
  90    --  address of the code from Loc.
  91    --  Do not add pragma Inline, see 9116-002.
  92    --  ??? This function will go away when 'Code_Address is fixed on VMS.
  93
  94    procedure Set_Machine_State (M : Machine_State);
  95    --  This routine sets M from the current machine state. It is called
  96    --  when an exception is initially signalled to initialize the state.
  97
  98 end System.Machine_State_Operations;