1 | /* Support macros for making weak and strong aliases for symbols, |
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2 | and for using symbol sets and linker warnings with GNU ld. |
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3 | Copyright (C) 1995,1996,1997,1998,2000,2001 Free Software Foundation, Inc. |
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4 | This file is part of the GNU C Library. |
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5 | |
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6 | The GNU C Library is free software; you can redistribute it and/or |
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7 | modify it under the terms of the GNU Lesser General Public |
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8 | License as published by the Free Software Foundation; either |
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9 | version 2.1 of the License, or (at your option) any later version. |
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10 | |
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11 | The GNU C Library is distributed in the hope that it will be useful, |
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12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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14 | Lesser General Public License for more details. |
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15 | |
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16 | You should have received a copy of the GNU Lesser General Public |
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17 | License along with the GNU C Library; if not, write to the Free |
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18 | Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
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19 | 02111-1307 USA. */ |
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20 | |
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21 | #ifndef _LIBC_SYMBOLS_H |
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22 | #define _LIBC_SYMBOLS_H 1 |
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23 | |
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24 | /* This file's macros are included implicitly in the compilation of every |
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25 | file in the C library by -imacros. |
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26 | |
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27 | We include config.h which is generated by configure. |
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28 | It should define for us the following symbols: |
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29 | |
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30 | * HAVE_ASM_SET_DIRECTIVE if we have `.set B, A' instead of `A = B'. |
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31 | * ASM_GLOBAL_DIRECTIVE with `.globl' or `.global'. |
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32 | * HAVE_GNU_LD if using GNU ld, with support for weak symbols in a.out, |
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33 | and for symbol set and warning messages extensions in a.out and ELF. |
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34 | * HAVE_ELF if using ELF, which supports weak symbols using `.weak'. |
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35 | * HAVE_ASM_WEAK_DIRECTIVE if we have weak symbols using `.weak'. |
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36 | * HAVE_ASM_WEAKEXT_DIRECTIVE if we have weak symbols using `.weakext'. |
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37 | |
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38 | */ |
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39 | |
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40 | /* This is defined for the compilation of all C library code. features.h |
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41 | tests this to avoid inclusion of stubs.h while compiling the library, |
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42 | before stubs.h has been generated. Some library code that is shared |
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43 | with other packages also tests this symbol to see if it is being |
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44 | compiled as part of the C library. We must define this before including |
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45 | config.h, because it makes some definitions conditional on whether libc |
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46 | itself is being compiled, or just some generator program. */ |
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47 | #define _LIBC 1 |
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48 | |
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49 | /* Enable declarations of GNU extensions, since we are compiling them. */ |
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50 | #define _GNU_SOURCE 1 |
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51 | /* And we also need the data for the reentrant functions. */ |
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52 | #define _REENTRANT 1 |
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53 | |
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54 | #include <config.h> |
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55 | |
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56 | /* The symbols in all the user (non-_) macros are C symbols. |
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57 | HAVE_GNU_LD without HAVE_ELF implies a.out. */ |
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58 | |
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59 | #if defined HAVE_ASM_WEAK_DIRECTIVE || defined HAVE_ASM_WEAKEXT_DIRECTIVE |
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60 | # define HAVE_WEAK_SYMBOLS |
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61 | #endif |
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62 | |
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63 | #ifndef __SYMBOL_PREFIX |
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64 | # ifdef NO_UNDERSCORES |
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65 | # define __SYMBOL_PREFIX |
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66 | # else |
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67 | # define __SYMBOL_PREFIX "_" |
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68 | # endif |
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69 | #endif |
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70 | |
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71 | #ifndef C_SYMBOL_NAME |
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72 | # ifdef NO_UNDERSCORES |
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73 | # define C_SYMBOL_NAME(name) name |
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74 | # else |
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75 | # define C_SYMBOL_NAME(name) _##name |
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76 | # endif |
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77 | #endif |
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78 | |
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79 | #ifndef ASM_LINE_SEP |
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80 | # define ASM_LINE_SEP ; |
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81 | #endif |
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82 | |
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83 | #ifndef C_SYMBOL_DOT_NAME |
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84 | # define C_SYMBOL_DOT_NAME(name) .##name |
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85 | #endif |
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86 | |
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87 | #ifndef __ASSEMBLER__ |
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88 | /* GCC understands weak symbols and aliases; use its interface where |
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89 | possible, instead of embedded assembly language. */ |
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90 | |
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91 | /* Define ALIASNAME as a strong alias for NAME. */ |
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92 | # define strong_alias(name, aliasname) _strong_alias(name, aliasname) |
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93 | # define _strong_alias(name, aliasname) \ |
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94 | extern __typeof (name) aliasname __attribute__ ((__alias__ (#name))); |
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95 | |
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96 | /* This comes between the return type and function name in |
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97 | a function definition to make that definition weak. */ |
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98 | # define weak_function __attribute__ ((__weak__)) |
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99 | # define weak_const_function __attribute__ ((__weak__, __const__)) |
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100 | |
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101 | # ifdef HAVE_WEAK_SYMBOLS |
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102 | |
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103 | /* Define ALIASNAME as a weak alias for NAME. |
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104 | If weak aliases are not available, this defines a strong alias. */ |
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105 | # define weak_alias(name, aliasname) _weak_alias (name, aliasname) |
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106 | # define _weak_alias(name, aliasname) \ |
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107 | extern __typeof (name) aliasname __attribute__ ((__weak__, __alias__ (#name))); |
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108 | |
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109 | /* Declare SYMBOL as weak undefined symbol (resolved to 0 if not defined). */ |
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110 | # define weak_extern(symbol) _weak_extern (symbol) |
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111 | # ifdef HAVE_ASM_WEAKEXT_DIRECTIVE |
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112 | # define _weak_extern(symbol) asm (".weakext " __SYMBOL_PREFIX #symbol); |
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113 | # else |
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114 | # define _weak_extern(symbol) asm (".weak " __SYMBOL_PREFIX #symbol); |
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115 | # endif |
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116 | |
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117 | # else |
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118 | |
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119 | # define weak_alias(name, aliasname) strong_alias(name, aliasname) |
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120 | # define weak_extern(symbol) /* Nothing. */ |
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121 | |
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122 | # endif |
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123 | |
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124 | #else /* __ASSEMBLER__ */ |
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125 | |
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126 | # ifdef HAVE_ASM_SET_DIRECTIVE |
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127 | # define strong_alias(original, alias) \ |
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128 | ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP \ |
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129 | .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original) |
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130 | # else |
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131 | # ifdef HAVE_ASM_GLOBAL_DOT_NAME |
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132 | # define strong_alias(original, alias) \ |
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133 | ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP \ |
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134 | C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) ASM_LINE_SEP \ |
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135 | ASM_GLOBAL_DIRECTIVE C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP \ |
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136 | C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original) |
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137 | # else |
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138 | # define strong_alias(original, alias) \ |
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139 | ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP \ |
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140 | C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) |
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141 | # endif |
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142 | # endif |
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143 | |
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144 | # ifdef HAVE_WEAK_SYMBOLS |
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145 | # ifdef HAVE_ASM_WEAKEXT_DIRECTIVE |
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146 | # define weak_alias(original, alias) \ |
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147 | .weakext C_SYMBOL_NAME (alias), C_SYMBOL_NAME (original) |
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148 | # define weak_extern(symbol) \ |
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149 | .weakext C_SYMBOL_NAME (symbol) |
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150 | |
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151 | # else /* ! HAVE_ASM_WEAKEXT_DIRECTIVE */ |
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152 | |
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153 | # ifdef HAVE_ASM_GLOBAL_DOT_NAME |
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154 | # define weak_alias(original, alias) \ |
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155 | .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP \ |
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156 | C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) ASM_LINE_SEP \ |
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157 | ASM_GLOBAL_DIRECTIVE C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP \ |
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158 | C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original) |
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159 | # else |
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160 | # define weak_alias(original, alias) \ |
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161 | .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP \ |
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162 | C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) |
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163 | # endif |
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164 | |
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165 | # define weak_extern(symbol) \ |
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166 | .weak C_SYMBOL_NAME (symbol) |
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167 | |
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168 | # endif /* ! HAVE_ASM_WEAKEXT_DIRECTIVE */ |
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169 | |
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170 | # else /* ! HAVE_WEAK_SYMBOLS */ |
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171 | |
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172 | # define weak_alias(original, alias) strong_alias(original, alias) |
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173 | # define weak_extern(symbol) /* Nothing */ |
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174 | # endif /* ! HAVE_WEAK_SYMBOLS */ |
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175 | |
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176 | #endif /* __ASSEMBLER__ */ |
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177 | |
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178 | /* On some platforms we can make internal function calls (i.e., calls of |
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179 | functions not exported) a bit faster by using a different calling |
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180 | convention. */ |
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181 | #ifndef internal_function |
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182 | # define internal_function /* empty */ |
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183 | #endif |
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184 | |
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185 | /* Prepare for the case that `__builtin_expect' is not available. */ |
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186 | #ifndef HAVE_BUILTIN_EXPECT |
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187 | # define __builtin_expect(expr, val) (expr) |
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188 | #endif |
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189 | |
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190 | /* Determine the return address. */ |
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191 | #define RETURN_ADDRESS(nr) \ |
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192 | __builtin_extract_return_addr (__builtin_return_address (nr)) |
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193 | |
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194 | /* When a reference to SYMBOL is encountered, the linker will emit a |
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195 | warning message MSG. */ |
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196 | #ifdef HAVE_GNU_LD |
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197 | # ifdef HAVE_ELF |
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198 | |
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199 | /* We want the .gnu.warning.SYMBOL section to be unallocated. */ |
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200 | # ifdef HAVE_ASM_PREVIOUS_DIRECTIVE |
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201 | # define __make_section_unallocated(section_string) \ |
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202 | asm (".section " section_string "\n\t.previous"); |
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203 | # elif defined HAVE_ASM_POPSECTION_DIRECTIVE |
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204 | # define __make_section_unallocated(section_string) \ |
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205 | asm (".pushsection " section_string "\n\t.popsection"); |
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206 | # else |
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207 | # define __make_section_unallocated(section_string) |
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208 | # endif |
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209 | |
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210 | /* Tacking on "\n\t#" to the section name makes gcc put it's bogus |
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211 | section attributes on what looks like a comment to the assembler. */ |
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212 | # ifdef HAVE_SECTION_QUOTES |
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213 | # define link_warning(symbol, msg) \ |
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214 | __make_section_unallocated (".gnu.warning." #symbol) \ |
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215 | static const char __evoke_link_warning_##symbol[] \ |
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216 | __attribute__ ((__section__ (".gnu.warning." #symbol "\"\n\t#\""))) = msg; |
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217 | # else |
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218 | # define link_warning(symbol, msg) \ |
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219 | __make_section_unallocated (".gnu.warning." #symbol) \ |
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220 | static const char __evoke_link_warning_##symbol[] \ |
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221 | __attribute__ ((__section__ (".gnu.warning." #symbol "\n\t#"))) = msg; |
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222 | # endif |
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223 | # else /* Not ELF: a.out */ |
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224 | # ifdef HAVE_XCOFF |
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225 | /* XCOFF does not support .stabs. |
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226 | The native aix linker will remove the .stab and .stabstr sections |
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227 | The gnu linker will have a fatal error if there is a relocation for |
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228 | symbol in the .stab section. Silently disable this macro. */ |
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229 | # define link_warning(symbol, msg) |
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230 | # else |
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231 | # define link_warning(symbol, msg) \ |
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232 | asm (".stabs \"" msg "\",30,0,0,0\n\t" \ |
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233 | ".stabs \"" __SYMBOL_PREFIX #symbol "\",1,0,0,0\n"); |
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234 | # endif /* XCOFF */ |
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235 | # endif |
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236 | #else |
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237 | /* We will never be heard; they will all die horribly. */ |
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238 | # define link_warning(symbol, msg) |
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239 | #endif |
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240 | |
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241 | /* A canned warning for sysdeps/stub functions. */ |
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242 | #define stub_warning(name) \ |
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243 | link_warning (name, \ |
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244 | "warning: " #name " is not implemented and will always fail") |
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245 | |
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246 | /* |
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247 | |
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248 | */ |
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249 | |
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250 | #ifdef HAVE_GNU_LD |
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251 | |
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252 | /* Symbol set support macros. */ |
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253 | |
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254 | # ifdef HAVE_ELF |
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255 | |
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256 | /* Make SYMBOL, which is in the text segment, an element of SET. */ |
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257 | # define text_set_element(set, symbol) _elf_set_element(set, symbol) |
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258 | /* Make SYMBOL, which is in the data segment, an element of SET. */ |
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259 | # define data_set_element(set, symbol) _elf_set_element(set, symbol) |
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260 | /* Make SYMBOL, which is in the bss segment, an element of SET. */ |
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261 | # define bss_set_element(set, symbol) _elf_set_element(set, symbol) |
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262 | |
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263 | /* These are all done the same way in ELF. |
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264 | There is a new section created for each set. */ |
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265 | # ifdef SHARED |
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266 | /* When building a shared library, make the set section writable, |
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267 | because it will need to be relocated at run time anyway. */ |
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268 | # define _elf_set_element(set, symbol) \ |
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269 | static const void *__elf_set_##set##_element_##symbol##__ \ |
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270 | __attribute__ ((__unused__, __section__ (#set))) = &(symbol) |
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271 | # else |
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272 | # define _elf_set_element(set, symbol) \ |
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273 | static const void *const __elf_set_##set##_element_##symbol##__ \ |
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274 | __attribute__ ((__unused__, __section__ (#set))) = &(symbol) |
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275 | # endif |
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276 | |
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277 | /* Define SET as a symbol set. This may be required (it is in a.out) to |
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278 | be able to use the set's contents. */ |
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279 | # define symbol_set_define(set) symbol_set_declare(set) |
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280 | |
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281 | /* Declare SET for use in this module, if defined in another module. */ |
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282 | # define symbol_set_declare(set) \ |
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283 | extern void *const __start_##set __attribute__ ((__weak__)); \ |
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284 | extern void *const __stop_##set __attribute__ ((__weak__)); \ |
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285 | weak_extern (__start_##set) weak_extern (__stop_##set) |
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286 | |
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287 | /* Return a pointer (void *const *) to the first element of SET. */ |
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288 | # define symbol_set_first_element(set) (&__start_##set) |
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289 | |
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290 | /* Return true iff PTR (a void *const *) has been incremented |
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291 | past the last element in SET. */ |
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292 | # define symbol_set_end_p(set, ptr) ((ptr) >= &__stop_##set) |
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293 | |
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294 | # else /* Not ELF: a.out. */ |
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295 | |
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296 | # ifdef HAVE_XCOFF |
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297 | /* XCOFF does not support .stabs. |
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298 | The native aix linker will remove the .stab and .stabstr sections |
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299 | The gnu linker will have a fatal error if there is a relocation for |
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300 | symbol in the .stab section. Silently disable these macros. */ |
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301 | # define text_set_element(set, symbol) |
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302 | # define data_set_element(set, symbol) |
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303 | # define bss_set_element(set, symbol) |
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304 | # else |
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305 | # define text_set_element(set, symbol) \ |
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306 | asm (".stabs \"" __SYMBOL_PREFIX #set "\",23,0,0," __SYMBOL_PREFIX #symbol) |
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307 | # define data_set_element(set, symbol) \ |
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308 | asm (".stabs \"" __SYMBOL_PREFIX #set "\",25,0,0," __SYMBOL_PREFIX #symbol) |
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309 | # define bss_set_element(set, symbol) ?error Must use initialized data. |
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310 | # endif /* XCOFF */ |
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311 | # define symbol_set_define(set) void *const (set)[1]; |
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312 | # define symbol_set_declare(set) extern void *const (set)[1]; |
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313 | |
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314 | # define symbol_set_first_element(set) &(set)[1] |
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315 | # define symbol_set_end_p(set, ptr) (*(ptr) == 0) |
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316 | |
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317 | # endif /* ELF. */ |
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318 | #else |
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319 | /* We cannot do anything in generial. */ |
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320 | # define text_set_element(set, symbol) asm ("") |
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321 | # define data_set_element(set, symbol) asm ("") |
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322 | # define bss_set_element(set, symbol) asm ("") |
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323 | # define symbol_set_define(set) void *const (set)[1]; |
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324 | # define symbol_set_declare(set) extern void *const (set)[1]; |
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325 | |
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326 | # define symbol_set_first_element(set) &(set)[1] |
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327 | # define symbol_set_end_p(set, ptr) (*(ptr) == 0) |
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328 | #endif /* Have GNU ld. */ |
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329 | |
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330 | #if DO_VERSIONING |
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331 | # define symbol_version(real, name, version) \ |
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332 | _symbol_version(real, name, version) |
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333 | # define default_symbol_version(real, name, version) \ |
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334 | _default_symbol_version(real, name, version) |
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335 | # ifdef __ASSEMBLER__ |
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336 | # define _symbol_version(real, name, version) \ |
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337 | .symver real, name##@##version |
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338 | # define _default_symbol_version(real, name, version) \ |
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339 | .symver real, name##@##@##version |
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340 | # else |
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341 | # define _symbol_version(real, name, version) \ |
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342 | __asm__ (".symver " #real "," #name "@" #version) |
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343 | # define _default_symbol_version(real, name, version) \ |
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344 | __asm__ (".symver " #real "," #name "@@" #version) |
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345 | # endif |
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346 | #else |
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347 | # define symbol_version(real, name, version) |
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348 | # define default_symbol_version(real, name, version) \ |
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349 | strong_alias(real, name) |
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350 | #endif |
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351 | |
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352 | #endif /* libc-symbols.h */ |
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