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564 lines
15 KiB
C++
564 lines
15 KiB
C++
// Functions for Exception Support for Java.
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/* Copyright (C) 1998, 1999, 2001 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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#include "unwind.h"
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// More nastiness: the GC wants to define TRUE and FALSE. We don't
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// need the Java definitions (themselves a hack), so we undefine them.
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#undef TRUE
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#undef FALSE
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extern "C"
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{
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#include <gc_priv.h>
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#include <gc_mark.h>
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#include <include/gc_gcj.h>
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};
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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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/* FIXME: Use the proper API to the collector. */
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java_exception_header *xh
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= static_cast<java_exception_header *>(GC_malloc (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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/* FIXME: If code == _URC_END_OF_STACK, then we reached top of
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stack without finding a handler for the exception. I seem to
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recall that Java has specific rules to handle this.
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If code is something else, we encountered some sort of heinous
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lossage, from which we could not recover. As is the way of such
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things we'll almost certainly have crashed before now, rather
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than actually being able to diagnose the problem. */
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abort ();
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}
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// ??? These ought to go somewhere else dwarf2 or dwarf2eh related.
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// Pointer encodings.
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#define DW_EH_PE_absptr 0x00
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#define DW_EH_PE_omit 0xff
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#define DW_EH_PE_uleb128 0x01
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#define DW_EH_PE_udata2 0x02
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#define DW_EH_PE_udata4 0x03
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#define DW_EH_PE_udata8 0x04
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#define DW_EH_PE_sleb128 0x09
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#define DW_EH_PE_sdata2 0x0A
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#define DW_EH_PE_sdata4 0x0B
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#define DW_EH_PE_sdata8 0x0C
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#define DW_EH_PE_signed 0x08
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#define DW_EH_PE_pcrel 0x10
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#define DW_EH_PE_textrel 0x20
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#define DW_EH_PE_datarel 0x30
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#define DW_EH_PE_funcrel 0x40
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static unsigned int
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size_of_encoded_value (unsigned char encoding)
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{
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switch (encoding & 0x07)
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{
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case DW_EH_PE_absptr:
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return sizeof (void *);
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case DW_EH_PE_udata2:
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return 2;
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case DW_EH_PE_udata4:
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return 4;
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case DW_EH_PE_udata8:
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return 8;
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}
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abort ();
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}
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static const unsigned char *
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read_encoded_value (_Unwind_Context *context, unsigned char encoding,
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const unsigned char *p, _Unwind_Ptr *val)
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{
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union unaligned
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{
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void *ptr;
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unsigned u2 __attribute__ ((mode (HI)));
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unsigned u4 __attribute__ ((mode (SI)));
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unsigned u8 __attribute__ ((mode (DI)));
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signed s2 __attribute__ ((mode (HI)));
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signed s4 __attribute__ ((mode (SI)));
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signed s8 __attribute__ ((mode (DI)));
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} __attribute__((__packed__));
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union unaligned *u = (union unaligned *) p;
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_Unwind_Ptr result;
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switch (encoding & 0x0f)
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{
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case DW_EH_PE_absptr:
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result = (_Unwind_Ptr) u->ptr;
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p += sizeof (void *);
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break;
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case DW_EH_PE_uleb128:
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{
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unsigned int shift = 0;
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unsigned char byte;
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result = 0;
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do
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{
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byte = *p++;
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result |= (_Unwind_Ptr)(byte & 0x7f) << shift;
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shift += 7;
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}
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while (byte & 0x80);
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}
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break;
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case DW_EH_PE_sleb128:
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{
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unsigned int shift = 0;
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unsigned char byte;
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result = 0;
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do
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{
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byte = *p++;
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result |= (_Unwind_Ptr)(byte & 0x7f) << shift;
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shift += 7;
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}
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while (byte & 0x80);
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if (shift < 8 * sizeof(result) && (byte & 0x40) != 0)
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result |= -(1L << shift);
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}
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break;
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case DW_EH_PE_udata2:
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result = u->u2;
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p += 2;
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break;
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case DW_EH_PE_udata4:
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result = u->u4;
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p += 4;
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break;
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case DW_EH_PE_udata8:
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result = u->u8;
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p += 8;
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break;
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case DW_EH_PE_sdata2:
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result = u->s2;
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p += 2;
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break;
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case DW_EH_PE_sdata4:
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result = u->s4;
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p += 4;
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break;
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case DW_EH_PE_sdata8:
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result = u->s8;
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p += 8;
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break;
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default:
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abort ();
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}
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if (result != 0)
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switch (encoding & 0xf0)
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{
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case DW_EH_PE_absptr:
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break;
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case DW_EH_PE_pcrel:
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// Define as relative to the beginning of the pointer.
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result += (_Unwind_Ptr) u;
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break;
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case DW_EH_PE_textrel:
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case DW_EH_PE_datarel:
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// FIXME.
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abort ();
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case DW_EH_PE_funcrel:
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result += _Unwind_GetRegionStart (context);
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break;
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default:
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abort ();
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}
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*val = result;
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return p;
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}
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static inline const unsigned char *
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read_uleb128 (const unsigned char *p, _Unwind_Ptr *val)
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{
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return read_encoded_value (0, DW_EH_PE_uleb128, p, val);
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}
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static inline const unsigned char *
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read_sleb128 (const unsigned char *p, _Unwind_Ptr *val)
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{
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return read_encoded_value (0, DW_EH_PE_sleb128, p, val);
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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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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_Ptr 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_Ptr 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, 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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signed long ar_filter, ar_disp;
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while (1)
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{
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_Unwind_Ptr tmp;
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p = action_record;
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p = read_sleb128 (p, &tmp); ar_filter = tmp;
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read_sleb128 (p, &tmp); ar_disp = tmp;
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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;
|
||
|
||
if (actions & _UA_SEARCH_PHASE)
|
||
{
|
||
if (! saw_handler)
|
||
return _URC_CONTINUE_UNWIND;
|
||
|
||
// For domestic exceptions, we cache data from phase 1 for phase 2.
|
||
if (exception_class == __gcj_exception_class)
|
||
{
|
||
xh->handlerSwitchValue = handler_switch_value;
|
||
xh->landingPad = landing_pad;
|
||
}
|
||
return _URC_HANDLER_FOUND;
|
||
}
|
||
|
||
install_context:
|
||
_Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
|
||
(_Unwind_Ptr) &xh->unwindHeader);
|
||
_Unwind_SetGR (context, __builtin_eh_return_data_regno (1),
|
||
handler_switch_value);
|
||
_Unwind_SetIP (context, landing_pad);
|
||
return _URC_INSTALL_CONTEXT;
|
||
}
|