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1 // Copyright (C) 1994-2017 Free Software Foundation, Inc.
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2 //
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3 // This file is part of GCC.
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4 //
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5 // GCC is free software; you can redistribute it and/or modify
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6 // it under the terms of the GNU General Public License as published by
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7 // the Free Software Foundation; either version 3, or (at your option)
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8 // any later version.
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9
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10 // GCC is distributed in the hope that it will be useful,
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11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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13 // GNU General Public License for more details.
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14
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15 // Under Section 7 of GPL version 3, you are granted additional
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16 // permissions described in the GCC Runtime Library Exception, version
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17 // 3.1, as published by the Free Software Foundation.
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18
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19 // You should have received a copy of the GNU General Public License and
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20 // a copy of the GCC Runtime Library Exception along with this program;
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21 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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22 // <http://www.gnu.org/licenses/>.
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23
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24 #include "tinfo.h"
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25
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26 namespace __cxxabiv1 {
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27
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28 __vmi_class_type_info::
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29 ~__vmi_class_type_info ()
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30 {}
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31
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32 __class_type_info::__sub_kind __vmi_class_type_info::
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33 __do_find_public_src (ptrdiff_t src2dst,
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34 const void *obj_ptr,
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35 const __class_type_info *src_type,
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36 const void *src_ptr) const
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37 {
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38 if (obj_ptr == src_ptr && *this == *src_type)
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39 return __contained_public;
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40
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41 for (std::size_t i = __base_count; i--;)
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42 {
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43 if (!__base_info[i].__is_public_p ())
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44 continue; // Not public, can't be here.
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45
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46 const void *base = obj_ptr;
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47 ptrdiff_t offset = __base_info[i].__offset ();
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48 bool is_virtual = __base_info[i].__is_virtual_p ();
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49
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50 if (is_virtual)
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51 {
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52 if (src2dst == -3)
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53 continue; // Not a virtual base, so can't be here.
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54 }
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55 base = convert_to_base (base, is_virtual, offset);
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56
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57 __sub_kind base_kind = __base_info[i].__base_type->__do_find_public_src
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58 (src2dst, base, src_type, src_ptr);
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59 if (contained_p (base_kind))
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60 {
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61 if (is_virtual)
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62 base_kind = __sub_kind (base_kind | __contained_virtual_mask);
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63 return base_kind;
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64 }
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65 }
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66
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67 return __not_contained;
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68 }
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69
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70 // This is a big hairy function. Although the run-time behaviour of
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71 // dynamic_cast is simple to describe, it gives rise to some non-obvious
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72 // behaviour. We also desire to determine as early as possible any definite
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73 // answer we can get. Because it is unknown what the run-time ratio of
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74 // succeeding to failing dynamic casts is, we do not know in which direction
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75 // to bias any optimizations. To that end we make no particular effort towards
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76 // early fail answers or early success answers. Instead we try to minimize
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77 // work by filling in things lazily (when we know we need the information),
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78 // and opportunisticly take early success or failure results.
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79 bool __vmi_class_type_info::
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80 __do_dyncast (ptrdiff_t src2dst,
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81 __sub_kind access_path,
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82 const __class_type_info *dst_type,
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83 const void *obj_ptr,
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84 const __class_type_info *src_type,
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85 const void *src_ptr,
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86 __dyncast_result &__restrict result) const
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87 {
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88 if (result.whole_details & __flags_unknown_mask)
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89 result.whole_details = __flags;
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90
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91 if (obj_ptr == src_ptr && *this == *src_type)
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92 {
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93 // The src object we started from. Indicate how we are accessible from
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94 // the most derived object.
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95 result.whole2src = access_path;
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96 return false;
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97 }
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98 if (*this == *dst_type)
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99 {
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100 result.dst_ptr = obj_ptr;
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101 result.whole2dst = access_path;
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102 if (src2dst >= 0)
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103 result.dst2src = adjust_pointer <void> (obj_ptr, src2dst) == src_ptr
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104 ? __contained_public : __not_contained;
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105 else if (src2dst == -2)
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106 result.dst2src = __not_contained;
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107 return false;
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108 }
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109
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110 // If src_type is a unique non-virtual base of dst_type, we have a good
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111 // guess at the address we want, so in the first pass try skipping any
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112 // bases which don't contain that address.
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113 const void *dst_cand = NULL;
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114 if (src2dst >= 0)
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115 dst_cand = adjust_pointer<void>(src_ptr, -src2dst);
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116 bool first_pass = true;
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117 bool skipped = false;
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118
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119 bool result_ambig = false;
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120 again:
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121 for (std::size_t i = __base_count; i--;)
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122 {
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123 __dyncast_result result2 (result.whole_details);
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124 void const *base = obj_ptr;
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125 __sub_kind base_access = access_path;
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126 ptrdiff_t offset = __base_info[i].__offset ();
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127 bool is_virtual = __base_info[i].__is_virtual_p ();
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128
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129 if (is_virtual)
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130 base_access = __sub_kind (base_access | __contained_virtual_mask);
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131 base = convert_to_base (base, is_virtual, offset);
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132
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133 if (dst_cand)
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134 {
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135 bool skip_on_first_pass = base > dst_cand;
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136 if (skip_on_first_pass == first_pass)
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137 {
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138 // We aren't interested in this base on this pass: either
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139 // we're on the first pass and this base doesn't contain the
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140 // likely address, or we're on the second pass and we checked
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141 // this base on the first pass.
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142 skipped = true;
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143 continue;
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144 }
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145 }
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146
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147 if (!__base_info[i].__is_public_p ())
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148 {
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149 if (src2dst == -2 &&
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150 !(result.whole_details
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151 & (__non_diamond_repeat_mask | __diamond_shaped_mask)))
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152 // The hierarchy has no duplicate bases (which might ambiguate
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153 // things) and where we started is not a public base of what we
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154 // want (so it cannot be a downcast). There is nothing of interest
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155 // hiding in a non-public base.
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156 continue;
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157 base_access = __sub_kind (base_access & ~__contained_public_mask);
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158 }
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159
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160 bool result2_ambig
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161 = __base_info[i].__base_type->__do_dyncast (src2dst, base_access,
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162 dst_type, base,
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163 src_type, src_ptr, result2);
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164 result.whole2src = __sub_kind (result.whole2src | result2.whole2src);
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165 if (result2.dst2src == __contained_public
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166 || result2.dst2src == __contained_ambig)
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167 {
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168 result.dst_ptr = result2.dst_ptr;
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169 result.whole2dst = result2.whole2dst;
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170 result.dst2src = result2.dst2src;
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171 // Found a downcast which can't be bettered or an ambiguous downcast
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172 // which can't be disambiguated
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173 return result2_ambig;
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174 }
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175
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176 if (!result_ambig && !result.dst_ptr)
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177 {
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178 // Not found anything yet.
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179 result.dst_ptr = result2.dst_ptr;
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180 result.whole2dst = result2.whole2dst;
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181 result_ambig = result2_ambig;
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182 if (result.dst_ptr && result.whole2src != __unknown
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183 && !(__flags & __non_diamond_repeat_mask))
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184 // Found dst and src and we don't have repeated bases.
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185 return result_ambig;
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186 }
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187 else if (result.dst_ptr && result.dst_ptr == result2.dst_ptr)
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188 {
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189 // Found at same address, must be via virtual. Pick the most
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190 // accessible path.
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191 result.whole2dst =
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192 __sub_kind (result.whole2dst | result2.whole2dst);
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193 }
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194 else if ((result.dst_ptr != 0 && result2.dst_ptr != 0)
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195 || (result.dst_ptr != 0 && result2_ambig)
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196 || (result2.dst_ptr != 0 && result_ambig))
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197 {
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198 // Found two different DST_TYPE bases, or a valid one and a set of
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199 // ambiguous ones, must disambiguate. See whether SRC_PTR is
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200 // contained publicly within one of the non-ambiguous choices. If it
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201 // is in only one, then that's the choice. If it is in both, then
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202 // we're ambiguous and fail. If it is in neither, we're ambiguous,
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203 // but don't yet fail as we might later find a third base which does
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204 // contain SRC_PTR.
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205
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206 __sub_kind new_sub_kind = result2.dst2src;
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207 __sub_kind old_sub_kind = result.dst2src;
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208
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209 if (contained_p (result.whole2src)
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210 && (!virtual_p (result.whole2src)
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211 || !(result.whole_details & __diamond_shaped_mask)))
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212 {
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213 // We already found SRC_PTR as a base of most derived, and
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214 // either it was non-virtual, or the whole hierarchy is
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215 // not-diamond shaped. Therefore if it is in either choice, it
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216 // can only be in one of them, and we will already know.
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217 if (old_sub_kind == __unknown)
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218 old_sub_kind = __not_contained;
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219 if (new_sub_kind == __unknown)
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220 new_sub_kind = __not_contained;
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221 }
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222 else
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223 {
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224 if (old_sub_kind >= __not_contained)
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225 ;// already calculated
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226 else if (contained_p (new_sub_kind)
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227 && (!virtual_p (new_sub_kind)
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228 || !(__flags & __diamond_shaped_mask)))
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229 // Already found inside the other choice, and it was
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230 // non-virtual or we are not diamond shaped.
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231 old_sub_kind = __not_contained;
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232 else
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233 old_sub_kind = dst_type->__find_public_src
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234 (src2dst, result.dst_ptr, src_type, src_ptr);
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235
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236 if (new_sub_kind >= __not_contained)
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237 ;// already calculated
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238 else if (contained_p (old_sub_kind)
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239 && (!virtual_p (old_sub_kind)
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240 || !(__flags & __diamond_shaped_mask)))
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241 // Already found inside the other choice, and it was
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242 // non-virtual or we are not diamond shaped.
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243 new_sub_kind = __not_contained;
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244 else
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245 new_sub_kind = dst_type->__find_public_src
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246 (src2dst, result2.dst_ptr, src_type, src_ptr);
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247 }
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248
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249 // Neither sub_kind can be contained_ambig -- we bail out early
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250 // when we find those.
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251 if (contained_p (__sub_kind (new_sub_kind ^ old_sub_kind)))
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252 {
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253 // Only on one choice, not ambiguous.
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254 if (contained_p (new_sub_kind))
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255 {
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256 // Only in new.
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257 result.dst_ptr = result2.dst_ptr;
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258 result.whole2dst = result2.whole2dst;
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259 result_ambig = false;
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260 old_sub_kind = new_sub_kind;
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261 }
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262 result.dst2src = old_sub_kind;
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263 if (public_p (result.dst2src))
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264 return false; // Can't be an ambiguating downcast for later discovery.
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265 if (!virtual_p (result.dst2src))
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266 return false; // Found non-virtually can't be bettered
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267 }
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268 else if (contained_p (__sub_kind (new_sub_kind & old_sub_kind)))
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269 {
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270 // In both.
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271 result.dst_ptr = NULL;
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272 result.dst2src = __contained_ambig;
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273 return true; // Fail.
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274 }
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275 else
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276 {
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277 // In neither publicly, ambiguous for the moment, but keep
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278 // looking. It is possible that it was private in one or
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279 // both and therefore we should fail, but that's just tough.
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280 result.dst_ptr = NULL;
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281 result.dst2src = __not_contained;
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282 result_ambig = true;
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283 }
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284 }
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285
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286 if (result.whole2src == __contained_private)
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287 // We found SRC_PTR as a private non-virtual base, therefore all
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288 // cross casts will fail. We have already found a down cast, if
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289 // there is one.
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290 return result_ambig;
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291 }
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292
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293 if (skipped && first_pass)
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294 {
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295 // We didn't find dst where we expected it, so let's go back and try
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296 // the bases we skipped (if any).
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297 first_pass = false;
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298 goto again;
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299 }
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300
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301 return result_ambig;
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302 }
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303
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304 bool __vmi_class_type_info::
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305 __do_upcast (const __class_type_info *dst, const void *obj_ptr,
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306 __upcast_result &__restrict result) const
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307 {
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308 if (__class_type_info::__do_upcast (dst, obj_ptr, result))
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309 return true;
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310
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311 int src_details = result.src_details;
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312 if (src_details & __flags_unknown_mask)
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313 src_details = __flags;
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314
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315 for (std::size_t i = __base_count; i--;)
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316 {
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317 __upcast_result result2 (src_details);
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318 const void *base = obj_ptr;
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319 ptrdiff_t offset = __base_info[i].__offset ();
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320 bool is_virtual = __base_info[i].__is_virtual_p ();
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321 bool is_public = __base_info[i].__is_public_p ();
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322
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323 if (!is_public && !(src_details & __non_diamond_repeat_mask))
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324 // original cannot have an ambiguous base, so skip private bases
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325 continue;
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326
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327 if (base)
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328 base = convert_to_base (base, is_virtual, offset);
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329
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330 if (__base_info[i].__base_type->__do_upcast (dst, base, result2))
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331 {
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332 if (result2.base_type == nonvirtual_base_type && is_virtual)
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333 result2.base_type = __base_info[i].__base_type;
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334 if (contained_p (result2.part2dst) && !is_public)
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335 result2.part2dst = __sub_kind (result2.part2dst & ~__contained_public_mask);
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336
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337 if (!result.base_type)
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338 {
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339 result = result2;
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340 if (!contained_p (result.part2dst))
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341 return true; // found ambiguously
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342
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343 if (result.part2dst & __contained_public_mask)
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344 {
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345 if (!(__flags & __non_diamond_repeat_mask))
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346 return true; // cannot have an ambiguous other base
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347 }
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348 else
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349 {
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350 if (!virtual_p (result.part2dst))
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351 return true; // cannot have another path
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352 if (!(__flags & __diamond_shaped_mask))
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353 return true; // cannot have a more accessible path
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354 }
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355 }
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356 else if (result.dst_ptr != result2.dst_ptr)
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357 {
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358 // Found an ambiguity.
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359 result.dst_ptr = NULL;
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360 result.part2dst = __contained_ambig;
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361 return true;
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362 }
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363 else if (result.dst_ptr)
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364 {
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365 // Ok, found real object via a virtual path.
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366 result.part2dst
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367 = __sub_kind (result.part2dst | result2.part2dst);
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368 }
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369 else
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370 {
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371 // Dealing with a null pointer, need to check vbase
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372 // containing each of the two choices.
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373 if (result2.base_type == nonvirtual_base_type
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374 || result.base_type == nonvirtual_base_type
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375 || !(*result2.base_type == *result.base_type))
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376 {
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377 // Already ambiguous, not virtual or via different virtuals.
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378 // Cannot match.
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379 result.part2dst = __contained_ambig;
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380 return true;
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381 }
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382 result.part2dst
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383 = __sub_kind (result.part2dst | result2.part2dst);
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384 }
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385 }
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386 }
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387 return result.part2dst != __unknown;
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388 }
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389
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390 }
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