------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME COMPONENTS -- -- -- -- S Y S T E M . E X C E P T I O N S -- -- -- -- S p e c -- -- -- -- -- -- Copyright (C) 1992-2000 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 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. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ -- This package contains definitions used for zero cost exception handling. -- See unit Ada.Exceptions for further details. Note that the reason that -- we separate out these definitions is to avoid problems with recursion -- in rtsfind. They must be in a unit which does not require any exception -- table generation of any kind. with Ada.Exceptions; with System; with System.Standard_Library; with Unchecked_Conversion; package System.Exceptions is package SSL renames System.Standard_Library; package AEX renames Ada.Exceptions; -- The following section defines data structures used for zero cost -- exception handling if System.Parameters.Zero_Cost_Exceptions is -- set true (i.e. zero cost exceptions are implemented on this target). -- The approach is to build tables that describe the PC ranges that -- are covered by various exception frames. When an exception occurs, -- these tables are searched to determine the address of the applicable -- handler for the current exception. subtype Handler_Loc is System.Address; -- Code location representing entry address of a handler. Values of -- this type are created using the N_Handler_Loc node, and then -- passed to the Enter_Handler procedure to enter a handler. 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. -------------------- -- Handler_Record -- -------------------- -- A Handler record is built for each choice for each exception handler -- in a frame. function To_Exception_Id is new Unchecked_Conversion (SSL.Exception_Data_Ptr, AEX.Exception_Id); Others_Dummy_Exception : aliased SSL.Exception_Data; Others_Id : constant AEX.Exception_Id := To_Exception_Id (Others_Dummy_Exception'Access); -- Dummy exception used to signal others exception All_Others_Dummy_Exception : aliased SSL.Exception_Data; All_Others_Id : constant AEX.Exception_Id := To_Exception_Id (All_Others_Dummy_Exception'Access); -- Dummy exception used to signal all others exception (including -- exceptions not normally handled by others, e.g. Abort_Signal) type Handler_Record is record Lo : Code_Loc; Hi : Code_Loc; -- Range of PC values of code covered by this handler record. The -- handler covers all code addresses that are greater than the Lo -- value, and less than or equal to the Hi value. Id : AEX.Exception_Id; -- Id of exception being handled, or one of the above special values Handler : Handler_Loc; -- Address of label at start of handler end record; type Handler_Record_Ptr is access all Handler_Record; type Handler_Record_List is array (Natural range <>) of Handler_Record_Ptr; --------------------------- -- Subprogram_Descriptor -- --------------------------- -- A Subprogram_Descriptor is built for each subprogram through which -- exceptions may propagate, this includes all Ada subprograms, -- and also all foreign language imported subprograms. subtype Subprogram_Info_Type is System.Address; -- This type is used to represent a value that is used to unwind stack -- frames. It references target dependent data that provides sufficient -- information (e.g. about the location of the return point, use of a -- frame pointer, save-over-call registers etc) to unwind the machine -- state to the caller. For some targets, this is simply a pointer to -- the entry point of the procedure (and the routine to pop the machine -- state disassembles the code at the entry point to obtain the required -- information). On other targets, it is a pointer to data created by the -- backend or assembler to represent the required information. No_Info : constant Subprogram_Info_Type := System.Null_Address; -- This is a special value used to indicate that it is not possible -- to pop past this frame. This is used at the outer level (e.g. for -- package elaboration procedures or the main procedure), and for any -- other foreign language procedure for which propagation is known -- to be impossible. An exception is considered unhandled if an -- attempt is made to pop a frame whose Subprogram_Info_Type value -- is set to No_Info. type Subprogram_Descriptor (Num_Handlers : Natural) is record Code : Code_Loc; -- This is a code location used to determine which procedure we are -- in. Most usually it is simply the entry address for the procedure. -- hA given address is considered to be within the procedure referenced -- by a Subprogram_Descriptor record if this is the descriptor for -- which the Code value is as large as possible without exceeding -- the given value. Subprogram_Info : Subprogram_Info_Type; -- This is a pointer to a target dependent data item that provides -- sufficient information for unwinding the stack frame of this -- procedure. A value of No_Info (zero) means that we are the -- outer level procedure. Handler_Records : Handler_Record_List (1 .. Num_Handlers); -- List of pointers to Handler_Records for this procedure. The array -- is sorted inside out, i.e. entries for inner frames appear before -- entries for outer handlers. This ensures that a serial search -- finds the innermost applicable handler end record; subtype Subprogram_Descriptor_0 is Subprogram_Descriptor (0); subtype Subprogram_Descriptor_1 is Subprogram_Descriptor (1); subtype Subprogram_Descriptor_2 is Subprogram_Descriptor (2); subtype Subprogram_Descriptor_3 is Subprogram_Descriptor (3); -- Predeclare commonly used subtypes for buildingt he tables type Subprogram_Descriptor_Ptr is access all Subprogram_Descriptor; type Subprogram_Descriptor_List is array (Natural range <>) of Subprogram_Descriptor_Ptr; type Subprogram_Descriptors_Record (Count : Natural) is record SDesc : Subprogram_Descriptor_List (1 .. Count); end record; type Subprogram_Descriptors_Ptr is access all Subprogram_Descriptors_Record; -------------------------- -- Unit Exception_Table -- -------------------------- -- If a unit contains at least one subprogram, then a library level -- declaration of the form: -- Tnn : aliased constant Subprogram_Descriptors := -- (Count => n, -- SDesc => -- (SD1'Unrestricted_Access, -- SD2'Unrestricted_Access, -- ... -- SDn'Unrestricted_Access)); -- pragma Export (Ada, Tnn, "__gnat_unit_name__SDP"); -- is generated where the initializing expression is an array aggregate -- whose elements are pointers to the generated subprogram descriptors -- for the units. -- Note: the ALI file contains the designation UX in each unit entry -- if a unit exception table is generated. -- The binder generates a list of addresses of pointers to these tables. end System.Exceptions;