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------------------------------------------------------------------------------

--                                                                          --

--                         GNAT COMPILER COMPONENTS                         --

--                                                                          --

--                      SYSTEM.MACHINE_STATE_OPERATIONS                     --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 1999-2009, Free Software Foundation, Inc.         --

--                                                                          --

-- 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 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/>.                                          --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

------------------------------------------------------------------------------

pragma Compiler_Unit;

pragma Polling (Off);

--  We must turn polling off for this unit, because otherwise we get

--  elaboration circularities with System.Exception_Tables.

with System.Storage_Elements;

package System.Machine_State_Operations is

   subtype Code_Loc is System.Address;

   --  Code location used in building exception tables and for call

   --  addresses when propagating an exception (also traceback table)

   --  Values of this type are created by using Label'Address or

   --  extracted from machine states using Get_Code_Loc.

   type Machine_State is new System.Address;

   --  The table based exception handling approach (see a-except.adb) isolates

   --  the target dependent aspects using an abstract data type interface

   --  to the type Machine_State, which is represented as a System.Address

   --  value (presumably implemented as a pointer to an appropriate record

   --  structure).

   function Machine_State_Length return System.Storage_Elements.Storage_Offset;

   --  Function to determine the length of the Storage_Array needed to hold

   --  a machine state. The machine state will always be maximally aligned.

   --  The value returned is a constant that will be used to allocate space

   --  for a machine state value.

   function Allocate_Machine_State return Machine_State;

   --  Allocate the required space for a Machine_State

   procedure Free_Machine_State (M : in out Machine_State);

   --  Free the dynamic memory taken by Machine_State

   --  The initial value of type Machine_State is created by the low level

   --  routine that actually raises an exception using the special builtin

   --  _builtin_machine_state. This value will typically encode the value

   --  of the program counter, and relevant registers. The following

   --  operations are defined on Machine_State values:

   function Get_Code_Loc (M : Machine_State) return Code_Loc;

   --  This function extracts the program counter value from a machine

   --  state, which the caller uses for searching the exception tables,

   --  and also for recording entries in the traceback table. The call

   --  returns a value of Null_Loc if the machine state represents the

   --  outer level, or some other frame for which no information can be

   --  provided.

   procedure Pop_Frame (M : Machine_State);

   --  This procedure pops the machine state M so that it represents the

   --  call point, as though the current subprogram had returned. It

   --  changes only the value referenced by M, and does not affect

   --  the current stack environment.

   function Fetch_Code (Loc : Code_Loc) return Code_Loc;

   --  Some architectures (notably VMS) use a descriptor to describe

   --  a subprogram address. This function computes the actual starting

   --  address of the code from Loc.

   --

   --  ??? This function will go away when 'Code_Address is fixed on VMS.

   --

   --  Do not add pragma Inline to this function: there is a curious

   --  interaction between rtsfind and front-end inlining. The exception

   --  declaration in s-auxdec calls rtsfind, which forces several other system

   --  packages to be compiled. Some of those have a pragma Inline, and we

   --  compile the corresponding bodies so that inlining can take place. One

   --  of these packages is s-mastop, which depends on s-auxdec, which is still

   --  being compiled: we have not seen all the declarations in it yet, so we

   --  get confused semantic errors.

   procedure Set_Machine_State (M : Machine_State);

   --  This routine sets M from the current machine state. It is called

   --  when an exception is initially signalled to initialize the state.

end System.Machine_State_Operations;