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-- --
-- --
-- S Y S T E M . E X C E P T I O N S . M A C H I N E --
-- --
-- S p e c --
-- --
-- Copyright (C) 2013-2021, 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 --
-- --
-- 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 --
-- <>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
-- Declaration of the machine exception and some associated facilities. The
-- machine exception is the object that is propagated by low level routines
-- and that contains the Ada exception occurrence.
-- This is the version using the GCC EH mechanism
with Ada.Unchecked_Conversion;
with Ada.Exceptions;
package System.Exceptions.Machine is
pragma Preelaborate;
-- Entities to interface with the GCC runtime --
-- These come from "C++ ABI for Itanium: Exception handling", which is
-- the reference for GCC.
-- Return codes from the GCC runtime functions used to propagate
-- an exception.
type Unwind_Reason_Code is
pragma Unreferenced
pragma Convention (C, Unwind_Reason_Code);
-- Mandatory common header for any exception object handled by the
-- GCC unwinding runtime.
type Exception_Class is mod 2 ** 64;
GNAT_Exception_Class : constant Exception_Class := 16#474e552d41646100#;
-- "GNU-Ada\0"
type Unwind_Word is mod 2 ** System.Word_Size;
for Unwind_Word'Size use System.Word_Size;
-- Map the corresponding C type used in Unwind_Exception below
type Unwind_Exception is record
Class : Exception_Class;
Cleanup : System.Address;
Private1 : Unwind_Word;
Private2 : Unwind_Word;
-- Usual exception structure has only two private fields, but the SEH
-- one has six. To avoid making this file more complex, we use six
-- fields on all platforms, wasting a few bytes on some.
Private3 : Unwind_Word;
Private4 : Unwind_Word;
Private5 : Unwind_Word;
Private6 : Unwind_Word;
end record;
pragma Convention (C, Unwind_Exception);
-- Map the GCC struct used for exception handling
for Unwind_Exception'Alignment use Standard'Maximum_Alignment;
-- The C++ ABI mandates the common exception header to be at least
-- doubleword aligned, and the libGCC implementation actually makes it
-- maximally aligned (see unwind.h). See additional comments on the
-- alignment below.
-- There is a subtle issue with the common header alignment, since the C
-- version is aligned on BIGGEST_ALIGNMENT, the Ada version is aligned on
-- Standard'Maximum_Alignment, and those two values don't quite represent
-- the same concepts and so may be decoupled someday. One typical reason
-- is that BIGGEST_ALIGNMENT may be larger than what the underlying system
-- allocator guarantees, and there are extra costs involved in allocating
-- objects aligned to such factors.
-- To deal with the potential alignment differences between the C and Ada
-- representations, the Ada part of the whole structure is only accessed
-- by the personality routine through accessors. Ada specific fields are
-- thus always accessed through consistent layout, and we expect the
-- actual alignment to always be large enough to avoid traps from the C
-- accesses to the common header. Besides, accessors alleviate the need
-- for a C struct whole counterpart, both painful and error-prone to
-- maintain anyway.
type GCC_Exception_Access is access all Unwind_Exception;
-- Pointer to a GCC exception
procedure Unwind_DeleteException (Excp : not null GCC_Exception_Access);
pragma Import (C, Unwind_DeleteException, "_Unwind_DeleteException");
-- Procedure to free any GCC exception
-- GNAT Specific Entities To Deal With The GCC EH Circuitry --
-- A GNAT exception object to be dealt with by the personality routine
-- called by the GCC unwinding runtime.
type GNAT_GCC_Exception is record
Header : Unwind_Exception;
-- ABI Exception header first
Occurrence : aliased Ada.Exceptions.Exception_Occurrence;
-- The Ada occurrence
end record;
pragma Convention (C, GNAT_GCC_Exception);
type GNAT_GCC_Exception_Access is access all GNAT_GCC_Exception;
function To_GCC_Exception is new
Ada.Unchecked_Conversion (System.Address, GCC_Exception_Access);
function To_GNAT_GCC_Exception is new
(GCC_Exception_Access, GNAT_GCC_Exception_Access);
function New_Occurrence return GNAT_GCC_Exception_Access;
-- Allocate and initialize a machine occurrence
end System.Exceptions.Machine;