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diff --git a/gcc/ada/s-mastop.ads b/gcc/ada/s-mastop.ads new file mode 100644 index 00000000000..ef0282bf524 --- /dev/null +++ b/gcc/ada/s-mastop.ads @@ -0,0 +1,165 @@ +------------------------------------------------------------------------------ +-- -- +-- GNAT COMPILER COMPONENTS -- +-- -- +-- SYSTEM.MACHINE_STATE_OPERATIONS -- +-- -- +-- S p e c -- +-- -- +-- $Revision: 1.4 $ +-- -- +-- Copyright (C) 1999-2001 Ada Core Technologies, 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 2, 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. See the GNU General Public License -- +-- for more details. You should have received a copy of the GNU General -- +-- Public License distributed with GNAT; see file COPYING. If not, write -- +-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- +-- MA 02111-1307, USA. -- +-- -- +-- As a special exception, if other files instantiate generics from this -- +-- unit, or you link this unit with other files to produce an executable, -- +-- this unit does not by itself cause the resulting executable to be -- +-- covered by the GNU General Public License. This exception does not -- +-- however invalidate any other reasons why the executable file might be -- +-- covered by the GNU Public License. -- +-- -- +-- GNAT was originally developed by the GNAT team at New York University. -- +-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). -- +-- -- +------------------------------------------------------------------------------ + +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; +with System.Exceptions; + +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; + Info : System.Exceptions.Subprogram_Info_Type); + -- 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. + -- + -- The Info parameter represents information generated by the backend + -- (see description of Subprogram_Info node in sinfo.ads). This + -- information is stored as static data during compilation. The + -- caller then passes this information to Pop_Frame, which will + -- use it to determine what must be changed in the machine state + -- (e.g. which save-over-call registers must be restored, and from + -- where on the stack frame they must be restored). + -- + -- A value of No_Info for Info means either that the backend provided + -- no information for current frame, or that the current frame is an + -- other language frame for which no information exists, or that this + -- is an outer level subprogram. In any case, Pop_Frame sets the code + -- location to Null_Address when it pops past such a frame, and this + -- is taken as an indication that the exception is unhandled. + + -- Note: at the current time, Info, if present is always a copy of + -- the entry point of the procedure, as found by searching the + -- subprogram table. For the case where a procedure is indeed in + -- the table (either it is an Ada procedure, or a foreign procedure + -- which is registered using pragma Propagate_Exceptions), then the + -- entry point information will indeed be correct. It may well be + -- possible for Pop_Frame to avoid using the Info parameter (for + -- example if it consults auxiliary Dwarf tables to do its job). + -- This is desirable if it can be done, because it means that it + -- will work fine to propagate exceptions through unregistered + -- foreign procedures. What will happen is that the search in the + -- Ada subprogram table will find a junk entry. Even if this junk + -- entry has an exception table, none of them will apply to the + -- current location, so they will be ignored, and then Pop_Frame + -- will be called to pop the frame. The Info parameter for this + -- call will be junk, but if it is not used that does not matter. + -- Note that the address recorded in the traceback table is of + -- the exception location, so the traceback will be correct even + -- in this case. + + procedure Enter_Handler + (M : Machine_State; + Handler : System.Exceptions.Handler_Loc); + -- When Propagate_Handler locates an applicable exception handler, it + -- calls Enter_Handler, passing it two parameters. The first is the + -- machine state that corresponds to what is required for entry to + -- the handler, as computed by repeated Pop_Frame calls to reach the + -- handler to be entered. The second is the code location for the + -- handler itself which is the address of the label at the start of + -- the handler code. + -- + -- Note: The machine state M is likely stored on the part of the + -- stack that will be popped by the call, so care must be taken + -- not to pop the stack until the Machine_State is entirely read. + -- The value passed as Handler was obtained from elaboration of + -- an N_Handler_Loc node by the backend. + + 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. + -- Do not add pragma Inline, see 9116-002. + -- ??? This function will go away when 'Code_Address is fixed on VMS. + + 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. + + procedure Set_Signal_Machine_State + (M : Machine_State; + Context : System.Address); + -- This routine sets M from the machine state that corresponds to the + -- point in the code where a signal was raised. The parameter Context + -- is a pointer to a structure created by the operating system when a + -- signal is raised, and made available to the signal handler. The + -- format of this context block, and the manner in which it is made + -- available to the handler, are implementation dependent. + +end System.Machine_State_Operations; |