unwind-c.c   [plain text]

/* Supporting functions for C exception handling.
   Copyright (C) 2002, 2003 Free Software Foundation, Inc.
   Contributed by Aldy Hernandez <aldy@quesejoda.com>.
   Shamelessly stolen from the Java front end.

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

In addition to the permissions in the GNU General Public License, the
Free Software Foundation gives you unlimited permission to link the
compiled version of this file into combinations with other programs,
and to distribute those combinations without any restriction coming
from the use of this file.  (The General Public License restrictions
do apply in other respects; for example, they cover modification of
the file, and distribution when not linked into a combined

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
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.  */

#include "tconfig.h"
#include "tsystem.h"
#include "unwind.h"
#include "unwind-pe.h"

typedef struct
  _Unwind_Ptr Start;
  _Unwind_Ptr LPStart;
  _Unwind_Ptr ttype_base;
  const unsigned char *TType;
  const unsigned char *action_table;
  unsigned char ttype_encoding;
  unsigned char call_site_encoding;
} lsda_header_info;

static const unsigned char *
parse_lsda_header (struct _Unwind_Context *context, const unsigned char *p,
		   lsda_header_info *info)
  _Unwind_Word tmp;
  unsigned char lpstart_encoding;

  info->Start = (context ? _Unwind_GetRegionStart (context) : 0);

  /* Find @LPStart, the base to which landing pad offsets are relative.  */
  lpstart_encoding = *p++;
  if (lpstart_encoding != DW_EH_PE_omit)
    p = read_encoded_value (context, lpstart_encoding, p, &info->LPStart);
    info->LPStart = info->Start;

  /* Find @TType, the base of the handler and exception spec type data.  */
  info->ttype_encoding = *p++;
  if (info->ttype_encoding != DW_EH_PE_omit)
      p = read_uleb128 (p, &tmp);
      info->TType = p + tmp;
    info->TType = 0;

  /* The encoding and length of the call-site table; the action table
     immediately follows.  */
  info->call_site_encoding = *p++;
  p = read_uleb128 (p, &tmp);
  info->action_table = p + tmp;

  return p;

#define PERSONALITY_FUNCTION    __gcc_personality_sj0
#define __builtin_eh_return_data_regno(x) x
#define PERSONALITY_FUNCTION    __gcc_personality_v0

PERSONALITY_FUNCTION (int, _Unwind_Action, _Unwind_Exception_Class,
		      struct _Unwind_Exception *, struct _Unwind_Context *);

		      _Unwind_Action actions,
		      _Unwind_Exception_Class exception_class ATTRIBUTE_UNUSED,
		      struct _Unwind_Exception *ue_header,
		      struct _Unwind_Context *context)
  lsda_header_info info;
  const unsigned char *language_specific_data, *p, *action_record;
  _Unwind_Ptr landing_pad, ip;

  if (version != 1)

  /* Currently we only support cleanups for C.  */
  if ((actions & _UA_CLEANUP_PHASE) == 0)

  language_specific_data = (const unsigned char *)
    _Unwind_GetLanguageSpecificData (context);

  /* If no LSDA, then there are no handlers or cleanups.  */
  if (! language_specific_data)

  /* Parse the LSDA header.  */
  p = parse_lsda_header (context, language_specific_data, &info);
  ip = _Unwind_GetIP (context) - 1;
  landing_pad = 0;

  /* The given "IP" is an index into the call-site table, with two
     exceptions -- -1 means no-action, and 0 means terminate.  But
     since we're using uleb128 values, we've not got random access
     to the array.  */
  if ((int) ip <= 0)
      _Unwind_Word cs_lp, cs_action;
	  p = read_uleb128 (p, &cs_lp);
	  p = read_uleb128 (p, &cs_action);
      while (--ip);

      /* Can never have null landing pad for sjlj -- that would have
	 been indicated by a -1 call site index.  */
      landing_pad = cs_lp + 1;
      if (cs_action)
	action_record = info.action_table + cs_action - 1;
      goto found_something;
  /* Search the call-site table for the action associated with this IP.  */
  while (p < info.action_table)
      _Unwind_Ptr cs_start, cs_len, cs_lp;
      _Unwind_Word cs_action;

      /* Note that all call-site encodings are "absolute" displacements.  */
      p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
      p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
      p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
      p = read_uleb128 (p, &cs_action);

      /* The table is sorted, so if we've passed the ip, stop.  */
      if (ip < info.Start + cs_start)
	p = info.action_table;
      else if (ip < info.Start + cs_start + cs_len)
	  if (cs_lp)
	    landing_pad = info.LPStart + cs_lp;
	  if (cs_action)
	    action_record = info.action_table + cs_action - 1;
	  goto found_something;

  /* IP is not in table.  No associated cleanups.  */
  /* ??? This is where C++ calls std::terminate to catch throw
     from a destructor.  */

  if (landing_pad == 0)
      /* IP is present, but has a null landing pad.
	 No handler to be run.  */
      return _URC_CONTINUE_UNWIND;

  _Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
		 (_Unwind_Ptr) ue_header);
  _Unwind_SetGR (context, __builtin_eh_return_data_regno (1), 0);
  _Unwind_SetIP (context, landing_pad);