1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT COMPILER COMPONENTS                         --
4--                                                                          --
5--                      SYSTEM.MACHINE_STATE_OPERATIONS                     --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--          Copyright (C) 1999-2013, 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 3,  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.                                     --
17--                                                                          --
18-- As a special exception under Section 7 of GPL version 3, you are granted --
19-- additional permissions described in the GCC Runtime Library Exception,   --
20-- version 3.1, as published by the Free Software Foundation.               --
21--                                                                          --
22-- You should have received a copy of the GNU General Public License and    --
23-- a copy of the GCC Runtime Library Exception along with this program;     --
24-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
25-- <http://www.gnu.org/licenses/>.                                          --
26--                                                                          --
27-- GNAT was originally developed  by the GNAT team at  New York University. --
28-- Extensive contributions were provided by Ada Core Technologies Inc.      --
29--                                                                          --
30------------------------------------------------------------------------------
31
32pragma Compiler_Unit_Warning;
33
34pragma Polling (Off);
35--  We must turn polling off for this unit, because otherwise we get
36--  elaboration circularities with System.Exception_Tables.
37
38with System.Storage_Elements;
39
40package 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   --
92   --  ??? This function will go away when 'Code_Address is fixed on VMS.
93   --
94   --  Do not add pragma Inline to this function: there is a curious
95   --  interaction between rtsfind and front-end inlining. The exception
96   --  declaration in s-auxdec calls rtsfind, which forces several other system
97   --  packages to be compiled. Some of those have a pragma Inline, and we
98   --  compile the corresponding bodies so that inlining can take place. One
99   --  of these packages is s-mastop, which depends on s-auxdec, which is still
100   --  being compiled: we have not seen all the declarations in it yet, so we
101   --  get confused semantic errors.
102
103   procedure Set_Machine_State (M : Machine_State);
104   --  This routine sets M from the current machine state. It is called
105   --  when an exception is initially signalled to initialize the state.
106
107end System.Machine_State_Operations;
108