369 lines
10 KiB
C
369 lines
10 KiB
C
/* The implementation of exception handling primitives for Objective-C.
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Copyright (C) 2004 Free Software Foundation, Inc.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the
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Free Software Foundation; either version 2, or (at your option) any
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later version.
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GCC is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
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License for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING. If not, write to
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the Free Software Foundation, 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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/* As a special exception, if you link this library with files compiled
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with GCC to produce an executable, this does not cause the resulting
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executable to be covered by the GNU General Public License. This
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exception does not however invalidate any other reasons why the
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executable file might be covered by the GNU General Public License. */
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#include <stdlib.h>
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#include "config.h"
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#include "objc/objc-api.h"
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#include "unwind.h"
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#include "unwind-pe.h"
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/* This is the exception class we report -- "GNUCOBJC". */
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#define __objc_exception_class \
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((((((((_Unwind_Exception_Class) 'G' \
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<< 8 | (_Unwind_Exception_Class) 'N') \
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<< 8 | (_Unwind_Exception_Class) 'U') \
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<< 8 | (_Unwind_Exception_Class) 'C') \
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<< 8 | (_Unwind_Exception_Class) 'O') \
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<< 8 | (_Unwind_Exception_Class) 'B') \
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<< 8 | (_Unwind_Exception_Class) 'J') \
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<< 8 | (_Unwind_Exception_Class) 'C')
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/* This is the object that is passed around by the Objective C runtime
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to represent the exception in flight. */
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struct ObjcException
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{
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/* This bit is needed in order to interact with the unwind runtime. */
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struct _Unwind_Exception base;
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/* The actual object we want to throw. */
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id value;
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/* Cache some internal unwind data between phase 1 and phase 2. */
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_Unwind_Ptr landingPad;
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int handlerSwitchValue;
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};
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struct lsda_header_info
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{
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_Unwind_Ptr Start;
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_Unwind_Ptr LPStart;
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_Unwind_Ptr ttype_base;
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const unsigned char *TType;
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const unsigned char *action_table;
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unsigned char ttype_encoding;
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unsigned char call_site_encoding;
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};
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static const unsigned char *
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parse_lsda_header (struct _Unwind_Context *context, const unsigned char *p,
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struct lsda_header_info *info)
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{
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_Unwind_Word tmp;
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unsigned char lpstart_encoding;
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info->Start = (context ? _Unwind_GetRegionStart (context) : 0);
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/* Find @LPStart, the base to which landing pad offsets are relative. */
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lpstart_encoding = *p++;
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if (lpstart_encoding != DW_EH_PE_omit)
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p = read_encoded_value (context, lpstart_encoding, p, &info->LPStart);
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else
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info->LPStart = info->Start;
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/* Find @TType, the base of the handler and exception spec type data. */
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info->ttype_encoding = *p++;
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if (info->ttype_encoding != DW_EH_PE_omit)
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{
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p = read_uleb128 (p, &tmp);
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info->TType = p + tmp;
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}
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else
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info->TType = 0;
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/* The encoding and length of the call-site table; the action table
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immediately follows. */
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info->call_site_encoding = *p++;
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p = read_uleb128 (p, &tmp);
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info->action_table = p + tmp;
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return p;
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}
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static Class
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get_ttype_entry (struct lsda_header_info *info, _Unwind_Word i)
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{
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_Unwind_Ptr ptr;
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i *= size_of_encoded_value (info->ttype_encoding);
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read_encoded_value_with_base (info->ttype_encoding, info->ttype_base,
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info->TType - i, &ptr);
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/* NULL ptr means catch-all. */
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if (ptr)
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return objc_get_class ((const char *) ptr);
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else
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return 0;
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}
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/* Like unto the method of the same name on Object, but takes an id. */
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/* ??? Does this bork the meta-type system? Can/should we look up an
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isKindOf method on the id? */
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static int
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isKindOf (id value, Class target)
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{
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Class c;
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/* NULL target is catch-all. */
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if (target == 0)
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return 1;
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for (c = value->class_pointer; c; c = class_get_super_class (c))
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if (c == target)
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return 1;
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return 0;
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}
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/* Using a different personality function name causes link failures
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when trying to mix code using different exception handling models. */
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#ifdef SJLJ_EXCEPTIONS
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#define PERSONALITY_FUNCTION __gnu_objc_personality_sj0
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#define __builtin_eh_return_data_regno(x) x
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#else
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#define PERSONALITY_FUNCTION __gnu_objc_personality_v0
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#endif
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_Unwind_Reason_Code
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PERSONALITY_FUNCTION (int version,
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_Unwind_Action actions,
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_Unwind_Exception_Class exception_class,
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struct _Unwind_Exception *ue_header,
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struct _Unwind_Context *context)
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{
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struct ObjcException *xh = (struct ObjcException *) ue_header;
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struct lsda_header_info info;
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const unsigned char *language_specific_data;
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const unsigned char *action_record;
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const unsigned char *p;
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_Unwind_Ptr landing_pad, ip;
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int handler_switch_value;
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int saw_cleanup, saw_handler;
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/* Interface version check. */
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if (version != 1)
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return _URC_FATAL_PHASE1_ERROR;
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/* Shortcut for phase 2 found handler for domestic exception. */
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if (actions == (_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME)
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&& exception_class == __objc_exception_class)
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{
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handler_switch_value = xh->handlerSwitchValue;
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landing_pad = xh->landingPad;
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goto install_context;
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}
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language_specific_data = (const unsigned char *)
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_Unwind_GetLanguageSpecificData (context);
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/* If no LSDA, then there are no handlers or cleanups. */
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if (! language_specific_data)
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return _URC_CONTINUE_UNWIND;
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/* Parse the LSDA header. */
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p = parse_lsda_header (context, language_specific_data, &info);
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info.ttype_base = base_of_encoded_value (info.ttype_encoding, context);
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ip = _Unwind_GetIP (context) - 1;
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landing_pad = 0;
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action_record = 0;
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handler_switch_value = 0;
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#ifdef SJLJ_EXCEPTIONS
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/* The given "IP" is an index into the call-site table, with two
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exceptions -- -1 means no-action, and 0 means terminate. But
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since we're using uleb128 values, we've not got random access
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to the array. */
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if ((int) ip < 0)
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return _URC_CONTINUE_UNWIND;
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else
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{
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_Unwind_Word cs_lp, cs_action;
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do
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{
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p = read_uleb128 (p, &cs_lp);
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p = read_uleb128 (p, &cs_action);
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}
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while (--ip);
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/* Can never have null landing pad for sjlj -- that would have
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been indicated by a -1 call site index. */
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landing_pad = cs_lp + 1;
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if (cs_action)
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action_record = info.action_table + cs_action - 1;
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goto found_something;
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}
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#else
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/* Search the call-site table for the action associated with this IP. */
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while (p < info.action_table)
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{
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_Unwind_Ptr cs_start, cs_len, cs_lp;
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_Unwind_Word cs_action;
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/* Note that all call-site encodings are "absolute" displacements. */
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p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
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p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
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p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
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p = read_uleb128 (p, &cs_action);
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/* The table is sorted, so if we've passed the ip, stop. */
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if (ip < info.Start + cs_start)
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p = info.action_table;
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else if (ip < info.Start + cs_start + cs_len)
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{
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if (cs_lp)
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landing_pad = info.LPStart + cs_lp;
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if (cs_action)
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action_record = info.action_table + cs_action - 1;
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goto found_something;
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}
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}
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#endif /* SJLJ_EXCEPTIONS */
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/* If ip is not present in the table, C++ would call terminate. */
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/* ??? As with Java, it's perhaps better to tweek the LSDA to
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that no-action is mapped to no-entry. */
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return _URC_CONTINUE_UNWIND;
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found_something:
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saw_cleanup = 0;
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saw_handler = 0;
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if (landing_pad == 0)
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{
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/* If ip is present, and has a null landing pad, there are
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no cleanups or handlers to be run. */
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}
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else if (action_record == 0)
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{
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/* If ip is present, has a non-null landing pad, and a null
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action table offset, then there are only cleanups present.
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Cleanups use a zero switch value, as set above. */
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saw_cleanup = 1;
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}
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else
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{
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/* Otherwise we have a catch handler. */
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_Unwind_Sword ar_filter, ar_disp;
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while (1)
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{
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p = action_record;
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p = read_sleb128 (p, &ar_filter);
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read_sleb128 (p, &ar_disp);
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if (ar_filter == 0)
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{
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/* Zero filter values are cleanups. */
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saw_cleanup = 1;
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}
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/* During forced unwinding, we only run cleanups. With a
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foreign exception class, we have no class info to match. */
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else if ((actions & _UA_FORCE_UNWIND)
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|| exception_class != __objc_exception_class)
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;
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else if (ar_filter > 0)
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{
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/* Positive filter values are handlers. */
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Class catch_type = get_ttype_entry (&info, ar_filter);
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if (isKindOf (xh->value, catch_type))
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{
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handler_switch_value = ar_filter;
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saw_handler = 1;
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break;
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}
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}
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else
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{
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/* Negative filter values are exception specifications,
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which Objective-C does not use. */
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abort ();
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}
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if (ar_disp == 0)
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break;
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action_record = p + ar_disp;
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}
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}
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if (! saw_handler && ! saw_cleanup)
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return _URC_CONTINUE_UNWIND;
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if (actions & _UA_SEARCH_PHASE)
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{
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if (!saw_handler)
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return _URC_CONTINUE_UNWIND;
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/* For domestic exceptions, we cache data from phase 1 for phase 2. */
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if (exception_class == __objc_exception_class)
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{
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xh->handlerSwitchValue = handler_switch_value;
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xh->landingPad = landing_pad;
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}
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return _URC_HANDLER_FOUND;
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}
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install_context:
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_Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
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__builtin_extend_pointer (xh->value));
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_Unwind_SetGR (context, __builtin_eh_return_data_regno (1),
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handler_switch_value);
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_Unwind_SetIP (context, landing_pad);
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return _URC_INSTALL_CONTEXT;
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}
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static void
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__objc_exception_cleanup (_Unwind_Reason_Code code __attribute__((unused)),
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struct _Unwind_Exception *exc)
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{
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free (exc);
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}
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void
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objc_exception_throw (id value)
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{
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struct ObjcException *header = calloc (1, sizeof (*header));
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header->base.exception_class = __objc_exception_class;
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header->base.exception_cleanup = __objc_exception_cleanup;
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header->value = value;
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#ifdef SJLJ_EXCEPTIONS
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_Unwind_SjLj_RaiseException (&header->base);
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#else
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_Unwind_RaiseException (&header->base);
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#endif
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/* Some sort of unwinding error. */
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abort ();
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}
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