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111
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1 /* Language-level data type conversion for GNU C.
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2 Copyright (C) 1987-2017 Free Software Foundation, Inc.
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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 under
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7 the terms of the GNU General Public License as published by the Free
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8 Software Foundation; either version 3, or (at your option) any later
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9 version.
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10
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11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
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13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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14 for more details.
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15
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16 You should have received a copy of the GNU General Public License
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17 along with GCC; see the file COPYING3. If not see
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18 <http://www.gnu.org/licenses/>. */
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19
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20
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21 /* This file contains the functions for converting C expressions
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22 to different data types. The only entry point is `convert'.
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23 Every language front end must have a `convert' function
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24 but what kind of conversions it does will depend on the language. */
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25
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26 #include "config.h"
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27 #include "system.h"
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28 #include "coretypes.h"
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29 #include "target.h"
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30 #include "c-tree.h"
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31 #include "convert.h"
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32 #include "langhooks.h"
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33 #include "ubsan.h"
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34 #include "stringpool.h"
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35 #include "attribs.h"
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36 #include "asan.h"
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37
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38 /* Change of width--truncation and extension of integers or reals--
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39 is represented with NOP_EXPR. Proper functioning of many things
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40 assumes that no other conversions can be NOP_EXPRs.
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41
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42 Conversion between integer and pointer is represented with CONVERT_EXPR.
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43 Converting integer to real uses FLOAT_EXPR
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44 and real to integer uses FIX_TRUNC_EXPR.
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45
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46 Here is a list of all the functions that assume that widening and
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47 narrowing is always done with a NOP_EXPR:
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48 In convert.c, convert_to_integer.
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49 In c-typeck.c, build_binary_op (boolean ops), and
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50 c_common_truthvalue_conversion.
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51 In expr.c: expand_expr, for operands of a MULT_EXPR.
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52 In fold-const.c: fold.
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53 In tree.c: get_narrower and get_unwidened. */
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54
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55 /* Subroutines of `convert'. */
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56
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57
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58
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59 /* Create an expression whose value is that of EXPR,
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60 converted to type TYPE. The TREE_TYPE of the value
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61 is always TYPE. This function implements all reasonable
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62 conversions; callers should filter out those that are
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63 not permitted by the language being compiled. */
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64
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65 tree
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66 convert (tree type, tree expr)
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67 {
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68 tree e = expr;
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69 enum tree_code code = TREE_CODE (type);
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70 const char *invalid_conv_diag;
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71 tree ret;
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72 location_t loc = EXPR_LOCATION (expr);
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73
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74 if (type == error_mark_node
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75 || error_operand_p (expr))
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76 return error_mark_node;
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77
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78 if ((invalid_conv_diag
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79 = targetm.invalid_conversion (TREE_TYPE (expr), type)))
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80 {
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81 error (invalid_conv_diag);
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82 return error_mark_node;
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83 }
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84
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85 if (type == TREE_TYPE (expr))
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86 return expr;
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87 ret = targetm.convert_to_type (type, expr);
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88 if (ret)
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89 return ret;
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90
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91 STRIP_TYPE_NOPS (e);
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92
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93 if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr))
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94 && (TREE_CODE (TREE_TYPE (expr)) != COMPLEX_TYPE
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95 || TREE_CODE (e) == COMPLEX_EXPR))
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96 return fold_convert_loc (loc, type, expr);
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97 if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
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98 return error_mark_node;
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99 if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
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100 {
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101 error ("void value not ignored as it ought to be");
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102 return error_mark_node;
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103 }
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104
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105 switch (code)
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106 {
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107 case VOID_TYPE:
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108 return fold_convert_loc (loc, type, e);
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109
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110 case INTEGER_TYPE:
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111 case ENUMERAL_TYPE:
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112 if (sanitize_flags_p (SANITIZE_FLOAT_CAST)
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113 && current_function_decl != NULL_TREE
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114 && TREE_CODE (TREE_TYPE (expr)) == REAL_TYPE
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115 && COMPLETE_TYPE_P (type))
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116 {
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117 expr = save_expr (expr);
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118 tree check = ubsan_instrument_float_cast (loc, type, expr);
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119 expr = fold_build1 (FIX_TRUNC_EXPR, type, expr);
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120 if (check == NULL_TREE)
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121 return expr;
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122 return fold_build2 (COMPOUND_EXPR, TREE_TYPE (expr), check, expr);
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123 }
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124 ret = convert_to_integer (type, e);
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125 goto maybe_fold;
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126
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127 case BOOLEAN_TYPE:
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128 return fold_convert_loc
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129 (loc, type, c_objc_common_truthvalue_conversion (input_location, expr));
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130
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131 case POINTER_TYPE:
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132 case REFERENCE_TYPE:
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133 ret = convert_to_pointer (type, e);
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134 goto maybe_fold;
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135
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136 case REAL_TYPE:
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137 ret = convert_to_real (type, e);
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138 goto maybe_fold;
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139
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140 case FIXED_POINT_TYPE:
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141 ret = convert_to_fixed (type, e);
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142 goto maybe_fold;
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143
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144 case COMPLEX_TYPE:
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145 ret = convert_to_complex (type, e);
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146 goto maybe_fold;
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147
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148 case VECTOR_TYPE:
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149 ret = convert_to_vector (type, e);
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150 goto maybe_fold;
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151
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152 case RECORD_TYPE:
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153 case UNION_TYPE:
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154 if (lang_hooks.types_compatible_p (type, TREE_TYPE (expr)))
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155 return e;
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156 break;
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157
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158 default:
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159 break;
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160
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161 maybe_fold:
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162 if (TREE_CODE (ret) != C_MAYBE_CONST_EXPR)
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163 ret = fold (ret);
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164 return ret;
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165 }
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166
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167 error ("conversion to non-scalar type requested");
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168 return error_mark_node;
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169 }
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