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111
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1 /* Exception handling and frame unwind runtime interface routines.
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131
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2 Copyright (C) 2001-2018 Free Software Foundation, Inc.
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111
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3
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4 This file is part of GCC.
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5
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6 GCC is free software; you can redistribute it and/or modify it
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7 under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 3, or (at your option)
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9 any later version.
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10
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11 GCC is distributed in the hope that it will be useful, but WITHOUT
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12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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13 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
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14 License for more details.
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15
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16 Under Section 7 of GPL version 3, you are granted additional
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17 permissions described in the GCC Runtime Library Exception, version
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18 3.1, as published by the Free Software Foundation.
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19
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20 You should have received a copy of the GNU General Public License and
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21 a copy of the GCC Runtime Library Exception along with this program;
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22 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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23 <http://www.gnu.org/licenses/>. */
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24
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25 /* @@@ Really this should be out of line, but this also causes link
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26 compatibility problems with the base ABI. This is slightly better
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27 than duplicating code, however. */
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28
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29 #ifndef GCC_UNWIND_PE_H
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30 #define GCC_UNWIND_PE_H
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31
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32 /* If using C++, references to abort have to be qualified with std::. */
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33 #if __cplusplus
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34 #define __gxx_abort std::abort
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35 #else
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36 #define __gxx_abort abort
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37 #endif
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38
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39 /* Pointer encodings, from dwarf2.h. */
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40 #define DW_EH_PE_absptr 0x00
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41 #define DW_EH_PE_omit 0xff
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42
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43 #define DW_EH_PE_uleb128 0x01
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44 #define DW_EH_PE_udata2 0x02
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45 #define DW_EH_PE_udata4 0x03
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46 #define DW_EH_PE_udata8 0x04
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47 #define DW_EH_PE_sleb128 0x09
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48 #define DW_EH_PE_sdata2 0x0A
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49 #define DW_EH_PE_sdata4 0x0B
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50 #define DW_EH_PE_sdata8 0x0C
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51 #define DW_EH_PE_signed 0x08
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52
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53 #define DW_EH_PE_pcrel 0x10
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54 #define DW_EH_PE_textrel 0x20
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55 #define DW_EH_PE_datarel 0x30
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56 #define DW_EH_PE_funcrel 0x40
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57 #define DW_EH_PE_aligned 0x50
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58
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59 #define DW_EH_PE_indirect 0x80
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60
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61
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62 #ifndef NO_SIZE_OF_ENCODED_VALUE
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63
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64 /* Given an encoding, return the number of bytes the format occupies.
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65 This is only defined for fixed-size encodings, and so does not
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66 include leb128. */
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67
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68 static unsigned int
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69 size_of_encoded_value (unsigned char encoding) __attribute__ ((unused));
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70
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71 static unsigned int
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72 size_of_encoded_value (unsigned char encoding)
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73 {
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74 if (encoding == DW_EH_PE_omit)
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75 return 0;
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76
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77 switch (encoding & 0x07)
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78 {
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79 case DW_EH_PE_absptr:
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80 return sizeof (void *);
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81 case DW_EH_PE_udata2:
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82 return 2;
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83 case DW_EH_PE_udata4:
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84 return 4;
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85 case DW_EH_PE_udata8:
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86 return 8;
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87 }
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88 __gxx_abort ();
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89 }
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90
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91 #endif
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92
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93 #ifndef NO_BASE_OF_ENCODED_VALUE
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94
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95 /* Given an encoding and an _Unwind_Context, return the base to which
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96 the encoding is relative. This base may then be passed to
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97 read_encoded_value_with_base for use when the _Unwind_Context is
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98 not available. */
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99
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100 static _Unwind_Ptr
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101 base_of_encoded_value (unsigned char encoding, struct _Unwind_Context *context)
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102 {
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103 if (encoding == DW_EH_PE_omit)
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104 return 0;
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105
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106 switch (encoding & 0x70)
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107 {
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108 case DW_EH_PE_absptr:
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109 case DW_EH_PE_pcrel:
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110 case DW_EH_PE_aligned:
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111 return 0;
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112
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113 case DW_EH_PE_textrel:
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114 return _Unwind_GetTextRelBase (context);
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115 case DW_EH_PE_datarel:
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116 return _Unwind_GetDataRelBase (context);
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117 case DW_EH_PE_funcrel:
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118 return _Unwind_GetRegionStart (context);
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119 }
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120 __gxx_abort ();
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121 }
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122
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123 #endif
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124
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125 /* Read an unsigned leb128 value from P, store the value in VAL, return
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126 P incremented past the value. We assume that a word is large enough to
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127 hold any value so encoded; if it is smaller than a pointer on some target,
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128 pointers should not be leb128 encoded on that target. */
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129
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130 static const unsigned char *
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131 read_uleb128 (const unsigned char *p, _uleb128_t *val)
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132 {
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133 unsigned int shift = 0;
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134 unsigned char byte;
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135 _uleb128_t result;
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136
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137 result = 0;
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138 do
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139 {
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140 byte = *p++;
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141 result |= ((_uleb128_t)byte & 0x7f) << shift;
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142 shift += 7;
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143 }
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144 while (byte & 0x80);
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145
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146 *val = result;
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147 return p;
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148 }
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149
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150 /* Similar, but read a signed leb128 value. */
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151
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152 static const unsigned char *
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153 read_sleb128 (const unsigned char *p, _sleb128_t *val)
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154 {
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155 unsigned int shift = 0;
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156 unsigned char byte;
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157 _uleb128_t result;
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158
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159 result = 0;
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160 do
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161 {
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162 byte = *p++;
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163 result |= ((_uleb128_t)byte & 0x7f) << shift;
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164 shift += 7;
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165 }
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166 while (byte & 0x80);
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167
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168 /* Sign-extend a negative value. */
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169 if (shift < 8 * sizeof(result) && (byte & 0x40) != 0)
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170 result |= -(((_uleb128_t)1L) << shift);
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171
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172 *val = (_sleb128_t) result;
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173 return p;
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174 }
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175
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176 /* Load an encoded value from memory at P. The value is returned in VAL;
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177 The function returns P incremented past the value. BASE is as given
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178 by base_of_encoded_value for this encoding in the appropriate context. */
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179
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180 static const unsigned char *
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181 read_encoded_value_with_base (unsigned char encoding, _Unwind_Ptr base,
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182 const unsigned char *p, _Unwind_Ptr *val)
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183 {
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184 union unaligned
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185 {
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186 void *ptr;
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187 unsigned u2 __attribute__ ((mode (HI)));
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188 unsigned u4 __attribute__ ((mode (SI)));
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189 unsigned u8 __attribute__ ((mode (DI)));
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190 signed s2 __attribute__ ((mode (HI)));
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191 signed s4 __attribute__ ((mode (SI)));
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192 signed s8 __attribute__ ((mode (DI)));
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193 } __attribute__((__packed__));
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194
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195 const union unaligned *u = (const union unaligned *) p;
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196 _Unwind_Internal_Ptr result;
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197
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198 if (encoding == DW_EH_PE_aligned)
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199 {
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200 _Unwind_Internal_Ptr a = (_Unwind_Internal_Ptr) p;
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201 a = (a + sizeof (void *) - 1) & - sizeof(void *);
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202 result = *(_Unwind_Internal_Ptr *) a;
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203 p = (const unsigned char *) (_Unwind_Internal_Ptr) (a + sizeof (void *));
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204 }
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205 else
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206 {
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207 switch (encoding & 0x0f)
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208 {
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209 case DW_EH_PE_absptr:
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210 result = (_Unwind_Internal_Ptr) u->ptr;
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211 p += sizeof (void *);
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212 break;
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213
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214 case DW_EH_PE_uleb128:
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215 {
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216 _uleb128_t tmp;
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217 p = read_uleb128 (p, &tmp);
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218 result = (_Unwind_Internal_Ptr) tmp;
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219 }
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220 break;
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221
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222 case DW_EH_PE_sleb128:
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223 {
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224 _sleb128_t tmp;
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225 p = read_sleb128 (p, &tmp);
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226 result = (_Unwind_Internal_Ptr) tmp;
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227 }
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228 break;
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229
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230 case DW_EH_PE_udata2:
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231 result = u->u2;
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232 p += 2;
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233 break;
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234 case DW_EH_PE_udata4:
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235 result = u->u4;
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236 p += 4;
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237 break;
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238 case DW_EH_PE_udata8:
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239 result = u->u8;
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240 p += 8;
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241 break;
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242
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243 case DW_EH_PE_sdata2:
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244 result = u->s2;
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245 p += 2;
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246 break;
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247 case DW_EH_PE_sdata4:
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248 result = u->s4;
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249 p += 4;
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250 break;
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251 case DW_EH_PE_sdata8:
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252 result = u->s8;
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253 p += 8;
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254 break;
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255
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256 default:
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257 __gxx_abort ();
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258 }
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259
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260 if (result != 0)
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261 {
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262 result += ((encoding & 0x70) == DW_EH_PE_pcrel
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263 ? (_Unwind_Internal_Ptr) u : base);
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264 if (encoding & DW_EH_PE_indirect)
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265 result = *(_Unwind_Internal_Ptr *) result;
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266 }
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267 }
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268
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269 *val = result;
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270 return p;
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271 }
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272
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273 #ifndef NO_BASE_OF_ENCODED_VALUE
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274
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275 /* Like read_encoded_value_with_base, but get the base from the context
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276 rather than providing it directly. */
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277
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278 static inline const unsigned char *
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279 read_encoded_value (struct _Unwind_Context *context, unsigned char encoding,
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280 const unsigned char *p, _Unwind_Ptr *val)
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281 {
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282 return read_encoded_value_with_base (encoding,
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283 base_of_encoded_value (encoding, context),
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284 p, val);
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285 }
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286
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287 #endif
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288
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289 #endif /* unwind-pe.h */
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