306 lines
7.6 KiB
C++
306 lines
7.6 KiB
C++
/* Exception handling and frame unwind runtime interface routines.
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Copyright (C) 2001-2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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/* @@@ Really this should be out of line, but this also causes link
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compatibility problems with the base ABI. This is slightly better
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than duplicating code, however. */
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/* If using C++, references to abort have to be qualified with std::. */
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#ifdef __cplusplus
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#define __gxx_abort std::abort
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#else
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#define __gxx_abort abort
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#endif
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/* Pointer encodings, from dwarf2.h. */
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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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#define DW_EH_PE_aligned 0x50
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#define DW_EH_PE_indirect 0x80
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#if defined(_LIBC)
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/* Prototypes. */
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extern unsigned int size_of_encoded_value (unsigned char encoding)
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attribute_hidden;
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extern const unsigned char *read_encoded_value_with_base
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(unsigned char encoding, _Unwind_Ptr base,
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const unsigned char *p, _Unwind_Ptr *val)
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attribute_hidden;
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extern const unsigned char * read_encoded_value
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(struct _Unwind_Context *context, unsigned char encoding,
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const unsigned char *p, _Unwind_Ptr *val)
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attribute_hidden;
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extern const unsigned char * read_uleb128 (const unsigned char *p,
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_Unwind_Word *val)
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attribute_hidden;
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extern const unsigned char * read_sleb128 (const unsigned char *p,
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_Unwind_Sword *val)
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attribute_hidden;
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#endif
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#if defined(_LIBC) && defined(_LIBC_DEFINITIONS)
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#ifdef _LIBC
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#define STATIC
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#else
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#define STATIC static
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#endif
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/* Given an encoding, return the number of bytes the format occupies.
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This is only defined for fixed-size encodings, and so does not
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include leb128. */
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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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if (encoding == DW_EH_PE_omit)
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return 0;
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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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__gxx_abort ();
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}
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#ifndef NO_BASE_OF_ENCODED_VALUE
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/* Given an encoding and an _Unwind_Context, return the base to which
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the encoding is relative. This base may then be passed to
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read_encoded_value_with_base for use when the _Unwind_Context is
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not available. */
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STATIC _Unwind_Ptr
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base_of_encoded_value (unsigned char encoding, struct _Unwind_Context *context)
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{
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if (encoding == DW_EH_PE_omit)
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return 0;
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switch (encoding & 0x70)
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{
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case DW_EH_PE_absptr:
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case DW_EH_PE_pcrel:
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case DW_EH_PE_aligned:
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return 0;
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case DW_EH_PE_textrel:
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return _Unwind_GetTextRelBase (context);
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case DW_EH_PE_datarel:
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return _Unwind_GetDataRelBase (context);
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case DW_EH_PE_funcrel:
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return _Unwind_GetRegionStart (context);
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}
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__gxx_abort ();
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}
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#endif
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/* Read an unsigned leb128 value from P, store the value in VAL, return
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P incremented past the value. We assume that a word is large enough to
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hold any value so encoded; if it is smaller than a pointer on some target,
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pointers should not be leb128 encoded on that target. */
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STATIC const unsigned char *
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read_uleb128 (const unsigned char *p, _Unwind_Word *val)
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{
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unsigned int shift = 0;
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unsigned char byte;
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_Unwind_Word result;
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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 |= (byte & 0x7f) << shift;
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shift += 7;
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}
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while (byte & 0x80);
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*val = result;
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return p;
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}
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/* Similar, but read a signed leb128 value. */
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STATIC const unsigned char *
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read_sleb128 (const unsigned char *p, _Unwind_Sword *val)
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{
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unsigned int shift = 0;
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unsigned char byte;
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_Unwind_Word result;
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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 |= (byte & 0x7f) << shift;
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shift += 7;
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}
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while (byte & 0x80);
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/* Sign-extend a negative value. */
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if (shift < 8 * sizeof (result) && (byte & 0x40) != 0)
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result |= -(1L << shift);
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*val = (_Unwind_Sword) result;
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return p;
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}
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/* Load an encoded value from memory at P. The value is returned in VAL;
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The function returns P incremented past the value. BASE is as given
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by base_of_encoded_value for this encoding in the appropriate context. */
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STATIC const unsigned char *
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read_encoded_value_with_base (unsigned char encoding, _Unwind_Ptr base,
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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_Internal_Ptr result;
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if (encoding == DW_EH_PE_aligned)
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{
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_Unwind_Internal_Ptr a = (_Unwind_Internal_Ptr) p;
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a = (a + sizeof (void *) - 1) & - sizeof (void *);
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result = *(_Unwind_Internal_Ptr *) a;
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p = (const unsigned char *) (a + sizeof (void *));
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}
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else
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{
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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_Internal_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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_Unwind_Word tmp;
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p = read_uleb128 (p, &tmp);
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result = (_Unwind_Internal_Ptr) tmp;
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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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_Unwind_Sword tmp;
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p = read_sleb128 (p, &tmp);
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result = (_Unwind_Internal_Ptr) tmp;
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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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__gxx_abort ();
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}
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if (result != 0)
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{
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result += ((encoding & 0x70) == DW_EH_PE_pcrel
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? (_Unwind_Internal_Ptr) u : base);
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if (encoding & DW_EH_PE_indirect)
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result = *(_Unwind_Internal_Ptr *) result;
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}
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}
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*val = result;
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return p;
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}
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#ifndef NO_BASE_OF_ENCODED_VALUE
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/* Like read_encoded_value_with_base, but get the base from the context
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rather than providing it directly. */
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STATIC const unsigned char *
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read_encoded_value (struct _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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return read_encoded_value_with_base (encoding,
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base_of_encoded_value (encoding, context),
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p, val);
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}
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#endif
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#endif /* _LIBC */
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