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/* Static condition handler for Alpha/VMS.

   Copyright (C) 2005-2009

   Free Software Foundation, Inc.

   This file is part of GCC.

   GCC is free software; you can redistribute it and/or modify it

   under the terms of the GNU General Public License as published

   by the Free Software Foundation; either version 3, or (at your

   option) any later version.

   GCC is distributed in the hope that it will be useful, but WITHOUT

   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY

   or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public

   License for more details.

   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/>.  */

/* This file implements __gcc_shell_handler, the static VMS condition handler

   used as the indirection wrapper around user level handlers installed with

   establish_vms_condition_handler GCC builtin.

   [ABI] in comments refers to the "HP OpenVMS calling standard" document

   dated January 2005.  */

#include <vms/chfdef.h>

#include <vms/pdscdef.h>

#include <vms/ssdef.h>

typedef void * ADDR;

typedef unsigned long long REG;

#define REG_AT(addr) (*(REG *)(addr))

/* Compute pointer to procedure descriptor (Procedure Value) from Frame

   Pointer FP, according to the rules in [ABI-3.5.1 Current Procedure].  */

#define PV_FOR(FP) \

  (((FP) != 0) \

    ? (((REG_AT (FP) & 0x7) == 0) ? *(PDSCDEF **)(FP) : (PDSCDEF *)(FP)) : 0)

long

__gcc_shell_handler (struct chf$signal_array *sig_arr,

                     struct chf$mech_array *mech_arr);

/* Helper for __gcc_shell_handler.  Fetch the pointer to procedure currently

   registered as the VMS condition handler for the live function with a frame

   pointer FP.  */

static ADDR

get_dyn_handler_pointer (REG fp)

{

  /* From the frame pointer we find the procedure descriptor, and fetch

     the handler_data field from there.  This field contains the offset

     from FP at which the address of the currently installed handler is

     to be found.  */

  PDSCDEF * pd = PV_FOR (fp);

  /* Procedure descriptor pointer for the live subprogram with FP as the frame

     pointer, and to which _gcc_shell_handler is attached as a condition

     handler.  */

  REG handler_slot_offset;

  /* Offset from FP at which the address of the currently established real

     condition handler is to be found.  This offset is available from the

     handler_data field of the procedure descriptor.  */

  REG handler_data_offset;

  /* The handler_data field position in the procedure descriptor, which

     depends on the kind of procedure at hand.  */

  switch (pd->pdsc$w_flags & 0xf)

    {

    case PDSC$K_KIND_FP_STACK:    /* [3.4.2 PD for stack frame procedures]  */

      handler_data_offset = 40;

      break;

    case PDSC$K_KIND_FP_REGISTER: /* [3.4.5 PD for reg frame procedures]  */

      handler_data_offset = 32;

      break;

    default:

      handler_data_offset = 0;

      break;

    }

  /* If we couldn't determine the handler_data field position, give up.  */

  if (handler_data_offset == 0)

    return 0;

  /* Otherwise, fetch the fp offset at which the real handler address is to be

     found, then fetch and return the latter in turn.  */

  handler_slot_offset = REG_AT ((REG)pd + handler_data_offset);

  return (ADDR) REG_AT (fp + handler_slot_offset);

}

/* The static VMS condition handler for GCC code.  Fetch the address of the

   currently established condition handler, then resignal if there is none or

   call the handler with the VMS condition arguments.  */

long

__gcc_shell_handler (struct chf$signal_array *sig_arr,

                     struct chf$mech_array *mech_arr)

{

  long ret;

  long (*user_handler) (struct chf$signal_array *, struct chf$mech_array *);

  user_handler = get_dyn_handler_pointer (mech_arr->chf$q_mch_frame);

  if (!user_handler)

    ret = SS$_RESIGNAL;

  else

    ret = user_handler (sig_arr, mech_arr);

  return ret;

}