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390 lines
11 KiB
C++
390 lines
11 KiB
C++
// Functions for Exception Support for Java.
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/* Copyright (C) 1998, 1999, 2001, 2002 Free Software Foundation
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This file is part of libgcj.
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This software is copyrighted work licensed under the terms of the
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Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
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details. */
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#include <config.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include <java/lang/Class.h>
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#include <java/lang/NullPointerException.h>
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#include <gcj/cni.h>
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#include <jvm.h>
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// unwind-pe.h uses std::abort(), but sometimes we compile libjava
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// without libstdc++-v3. The following hack forces it to use
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// stdlib.h's abort().
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namespace std
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{
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__attribute__ ((__noreturn__)) void abort ()
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{
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::abort ();
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}
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}
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#include "unwind.h"
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struct alignment_test_struct
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{
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char space;
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char end[0] __attribute__((aligned));
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};
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struct java_exception_header
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{
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/* Cache handler details between Phase 1 and Phase 2. */
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_Unwind_Ptr landingPad;
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int handlerSwitchValue;
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/* The object being thrown. Compiled code expects this to be immediately
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before the generic exception header. Which is complicated by the fact
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that _Unwind_Exception is ((aligned)). */
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char pad[sizeof(jthrowable) < sizeof(alignment_test_struct)
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? sizeof(alignment_test_struct) - sizeof(jthrowable) : 0]
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__attribute__((aligned));
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jthrowable value;
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/* The generic exception header. */
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_Unwind_Exception unwindHeader;
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};
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// This is the exception class we report -- "GNUCJAVA".
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const _Unwind_Exception_Class __gcj_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) 'J')
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<< 8 | (_Unwind_Exception_Class) 'A')
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<< 8 | (_Unwind_Exception_Class) 'V')
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<< 8 | (_Unwind_Exception_Class) 'A');
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static inline java_exception_header *
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get_exception_header_from_ue (_Unwind_Exception *exc)
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{
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return reinterpret_cast<java_exception_header *>(exc + 1) - 1;
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}
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/* Perform a throw, Java style. Throw will unwind through this call,
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so there better not be any handlers or exception thrown here. */
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extern "C" void
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_Jv_Throw (jthrowable value)
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{
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java_exception_header *xh
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= static_cast<java_exception_header *>(_Jv_AllocRawObj (sizeof (*xh)));
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if (value == NULL)
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value = new java::lang::NullPointerException ();
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xh->value = value;
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xh->unwindHeader.exception_class = __gcj_exception_class;
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xh->unwindHeader.exception_cleanup = NULL;
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/* We're happy with setjmp/longjmp exceptions or region-based
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exception handlers: entry points are provided here for both. */
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_Unwind_Reason_Code code;
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#ifdef SJLJ_EXCEPTIONS
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code = _Unwind_SjLj_RaiseException (&xh->unwindHeader);
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#else
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code = _Unwind_RaiseException (&xh->unwindHeader);
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#endif
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/* If code == _URC_END_OF_STACK, then we reached top of stack without
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finding a handler for the exception. Since each thread is run in
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a try/catch, this oughtn't happen. If code is something else, we
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encountered some sort of heinous lossage from which we could not
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recover. As is the way of such things, almost certainly we will have
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crashed before now, rather than actually being able to diagnose the
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problem. */
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abort();
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}
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#include "unwind-pe.h"
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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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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 (_Unwind_Context *context, const unsigned char *p,
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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 jclass
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get_ttype_entry (_Unwind_Context *context, lsda_header_info *info, long 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 (context, info->ttype_encoding, info->TType - i, &ptr);
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return reinterpret_cast<jclass>(ptr);
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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 __gcj_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 __gcj_personality_v0
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#endif
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extern "C" _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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java_exception_header *xh = get_exception_header_from_ue (ue_header);
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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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bool saw_cleanup;
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bool 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 == __gcj_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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// FIXME: In Phase 1, record _Unwind_GetIP in xh->obj as a part of
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// the stack trace for this exception. This will only collect Java
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// frames, but perhaps that is acceptable.
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// FIXME2: _Unwind_GetIP is nonsensical for SJLJ, being a call-site
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// index instead of a PC value. We could perhaps arrange for
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// _Unwind_GetRegionStart to return context->fc->jbuf[1], which
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// is the address of the handler label for __builtin_longjmp, but
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// there is no solution for DONT_USE_BUILTIN_SETJMP.
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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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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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// ??? It is perhaps better to tweek the LSDA so that no-action
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// is mapped to no-entry for Java.
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return _URC_CONTINUE_UNWIND;
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found_something:
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saw_cleanup = false;
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saw_handler = false;
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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 = true;
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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 = true;
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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 != __gcj_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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jclass catch_type = get_ttype_entry (context, &info, ar_filter);
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// The catch_type is either a (java::lang::Class*) or
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// is one more than a (Utf8Const*).
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if ((size_t)catch_type & 1)
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catch_type = _Jv_FindClass ((Utf8Const*)catch_type - 1, NULL);
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if (_Jv_IsInstanceOf (xh->value, catch_type))
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{
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handler_switch_value = ar_filter;
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saw_handler = true;
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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 Java does not use.
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// ??? Perhaps better to make them an index into a table
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// of null-terminated strings instead of playing games
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// with Utf8Const+1 as above.
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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 == __gcj_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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(_Unwind_Ptr) &xh->unwindHeader);
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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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