unwind.inc   [plain text]

/* Exception handling and frame unwind runtime interface routines. -*- C -*-
   Copyright (C) 2001 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 2, 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.

   You should have received a copy of the GNU General Public License
   along with GCC; see the file COPYING.  If not, write to the Free
   Software Foundation, 59 Temple Place - Suite 330, Boston, MA
   02111-1307, USA.  */

/* This is derived from the C++ ABI for IA-64.  Where we diverge
   for cross-architecture compatibility are noted with "@@@".  
   This file is included from unwind-dw2.c or unwind-ia64.c.  */

/* Subroutine of _Unwind_RaiseException also invoked from _Unwind_Resume. 

   Unwind the stack calling the personality routine to find both the
   exception handler and intermediary cleanup code.  We'll only locate
   the first such frame here.  Cleanup code will call back into
   _Unwind_Resume and we'll continue Phase 2 there.  */

static _Unwind_Reason_Code
_Unwind_RaiseException_Phase2(struct _Unwind_Exception *exc,
			      struct _Unwind_Context *context)
{
  _Unwind_Reason_Code code;

  Dprintf("in _Unwind_RaiseException_Phase2\n");
  while (1)
    {
      _Unwind_FrameState fs;
      int match_handler;

      code = uw_frame_state_for (context, &fs);

      Dprintf("got frame state in _Unwind_RaiseException_Phase2\n");
      /* Identify when we've reached the designated handler context.  */
      match_handler = (uw_identify_context (context) == exc->private_2
		       ? _UA_HANDLER_FRAME : 0);

      if (code != _URC_NO_REASON)
	{
	  Dprintf("some error encountered\n");
	/* Some error encountered.  Usually the unwinder doesn't
	   diagnose these and merely crashes.  */
	return _URC_FATAL_PHASE2_ERROR;
	}
      Dprintf("about to run personality %p, context %p\n", (void *)fs.personality, context);
      /* Unwind successful.  Run the personality routine, if any.  */
      if (fs.personality)
	{
	  code = (*fs.personality) (1, _UA_CLEANUP_PHASE | match_handler,
				    exc->exception_class, exc, context);
	  Dprintf("personality returns %d (m_h is %d)\n", code, match_handler);
	  if (code == _URC_INSTALL_CONTEXT)
	    break;
	  if (code != _URC_CONTINUE_UNWIND) 
	    return _URC_FATAL_PHASE2_ERROR;
	}

      /* Don't let us unwind past the handler context.  */
      if (match_handler)
	abort ();

      uw_update_context (context, &fs);
    }

  return code;
}


/* Raise an exception, passing along the given exception object.  */

_Unwind_Reason_Code
_Unwind_RaiseException(struct _Unwind_Exception *exc)
{
  struct _Unwind_Context this_context, cur_context;
  _Unwind_Reason_Code code;

  Dprintf("begin unwind exc %p\n", exc);
  uw_init_context (&this_context);
  Dprintf("in _Unwind_RaiseException begin, set context %p from %p\n",
	 &cur_context, &this_context);
  cur_context = this_context;

  Dprintf("begin search, exc %p\n", exc);
  /* Phase 1: Search.  Unwind the stack, calling the personality routine
     with the _UA_SEARCH_PHASE flag set.  Do not modify the stack yet.  */
  while (1)
    {
      _Unwind_FrameState fs;

      code = uw_frame_state_for (&cur_context, &fs);

      Dprintf("got a frame state\n");
      if (code == _URC_END_OF_STACK)
	/* Hit end of stack with no handler found.  */
	return _URC_END_OF_STACK;

      if (code != _URC_NO_REASON)
	/* Some error encountered.  Ususally the unwinder doesn't
	   diagnose these and merely crashes.  */
	return _URC_FATAL_PHASE1_ERROR;

      /* Unwind successful.  Run the personality routine, if any.  */
      if (fs.personality)
	{
	  code = (*fs.personality) (1, _UA_SEARCH_PHASE, exc->exception_class,
				    exc, &cur_context);
	  if (code == _URC_HANDLER_FOUND)
	    break;
	  else if (code != _URC_CONTINUE_UNWIND)
	    return _URC_FATAL_PHASE1_ERROR;
	}

      uw_update_context (&cur_context, &fs);
    }
  Dprintf("finished search\n");
  /* Indicate to _Unwind_Resume and associated subroutines that this
     is not a forced unwind.  Further, note where we found a handler.  */
  exc->private_1 = 0;
  exc->private_2 = uw_identify_context (&cur_context);

  Dprintf("in _Unwind_RaiseException begin, set context %p from %p\n",
	 &cur_context, &this_context);
  cur_context = this_context;
  code = _Unwind_RaiseException_Phase2 (exc, &cur_context);
  if (code != _URC_INSTALL_CONTEXT)
    return code;

  Dprintf("about to install context, this=%p, cur=%p\n",
	 &this_context, &cur_context);
  uw_install_context (&this_context, &cur_context);
}


/* Subroutine of _Unwind_ForcedUnwind also invoked from _Unwind_Resume.  */

static _Unwind_Reason_Code
_Unwind_ForcedUnwind_Phase2(struct _Unwind_Exception *exc,
			    struct _Unwind_Context *context)
{
  _Unwind_Stop_Fn stop = (_Unwind_Stop_Fn) (_Unwind_Ptr) exc->private_1;
  void *stop_argument = (void *) (_Unwind_Ptr) exc->private_2;
  _Unwind_Reason_Code code, stop_code;

  while (1)
    {
      _Unwind_FrameState fs;
      int action;

      code = uw_frame_state_for (context, &fs);
      if (code != _URC_NO_REASON && code != _URC_END_OF_STACK)
	return _URC_FATAL_PHASE2_ERROR;

      /* Unwind successful.  */
      action = _UA_FORCE_UNWIND | _UA_CLEANUP_PHASE;
      if (code == _URC_END_OF_STACK)
	action |= _UA_END_OF_STACK;
      stop_code = (*stop) (1, action, exc->exception_class, exc,
			   context, stop_argument);
      if (stop_code != _URC_NO_REASON)
	return _URC_FATAL_PHASE2_ERROR;

      /* Stop didn't want to do anything.  Invoke the personality
	 handler, if applicable, to run cleanups.  */
      if (code == _URC_END_OF_STACK)
	break;
	
      if (fs.personality)
	{
	  code = (*fs.personality) (1, _UA_FORCE_UNWIND | _UA_CLEANUP_PHASE,
				    exc->exception_class, exc, context);
	  if (code == _URC_INSTALL_CONTEXT)
	    break;
	  if (code != _URC_CONTINUE_UNWIND) 
	    return _URC_FATAL_PHASE2_ERROR;
	}

      uw_update_context (context, &fs);
    }

  return code;
}


/* Raise an exception for forced unwinding.  */

_Unwind_Reason_Code
_Unwind_ForcedUnwind (struct _Unwind_Exception *exc,
		      _Unwind_Stop_Fn stop, void * stop_argument)
{
  struct _Unwind_Context this_context, cur_context;
  _Unwind_Reason_Code code;

  uw_init_context (&this_context);
  cur_context = this_context;

  exc->private_1 = (_Unwind_Ptr) stop;
  exc->private_2 = (_Unwind_Ptr) stop_argument;

  code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context);
  if (code != _URC_INSTALL_CONTEXT)
    return code;

  uw_install_context (&this_context, &cur_context);
}


/* Resume propagation of an existing exception.  This is used after
   e.g. executing cleanup code, and not to implement rethrowing.  */

void
_Unwind_Resume (struct _Unwind_Exception *exc)
{
  struct _Unwind_Context this_context, cur_context;
  _Unwind_Reason_Code code;

  Dprintf("_Unwind_Resume begin exc %p\n", exc);
  uw_init_context (&this_context);
  cur_context = this_context;

  Dprintf("_Unwind_Resume after init context exc %p cur_context %p\n",
	 exc, &cur_context);

  /* Choose between continuing to process _Unwind_RaiseException
     or _Unwind_ForcedUnwind.  */
  if (exc->private_1 == 0)
    code = _Unwind_RaiseException_Phase2 (exc, &cur_context);
  else
    code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context);

  if (code != _URC_INSTALL_CONTEXT)
    abort ();

  uw_install_context (&this_context, &cur_context);
}

/* A convenience function that calls the exception_cleanup field.  */

void
_Unwind_DeleteException (struct _Unwind_Exception *exc)
{
  (*exc->exception_cleanup) (_URC_FOREIGN_EXCEPTION_CAUGHT, exc);
}