1 | /* Specialized bits of code needed to support construction and |
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2 | destruction of file-scope objects in C++ code. |
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3 | Copyright (C) 1991, 94, 95, 96, 97, 1998 Free Software Foundation, Inc. |
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4 | Contributed by Ron Guilmette (rfg@monkeys.com). |
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5 | |
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6 | This file is part of GNU CC. |
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7 | |
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8 | GNU CC is free software; you can redistribute it and/or modify |
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9 | it under the terms of the GNU General Public License as published by |
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10 | the Free Software Foundation; either version 2, or (at your option) |
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11 | any later version. |
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12 | |
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13 | GNU CC is distributed in the hope that it will be useful, |
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14 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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16 | GNU General Public License for more details. |
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17 | |
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18 | You should have received a copy of the GNU General Public License |
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19 | along with GNU CC; see the file COPYING. If not, write to |
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20 | the Free Software Foundation, 59 Temple Place - Suite 330, |
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21 | Boston, MA 02111-1307, USA. */ |
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22 | |
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23 | /* As a special exception, if you link this library with files |
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24 | compiled with GCC to produce an executable, this does not cause |
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25 | the resulting executable to be covered by the GNU General Public License. |
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26 | This exception does not however invalidate any other reasons why |
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27 | the executable file might be covered by the GNU General Public License. */ |
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28 | |
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29 | /* This file is a bit like libgcc1.c/libgcc2.c in that it is compiled |
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30 | multiple times and yields multiple .o files. |
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31 | |
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32 | This file is useful on target machines where the object file format |
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33 | supports multiple "user-defined" sections (e.g. COFF, ELF, ROSE). On |
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34 | such systems, this file allows us to avoid running collect (or any |
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35 | other such slow and painful kludge). Additionally, if the target |
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36 | system supports a .init section, this file allows us to support the |
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37 | linking of C++ code with a non-C++ main program. |
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38 | |
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39 | Note that if INIT_SECTION_ASM_OP is defined in the tm.h file, then |
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40 | this file *will* make use of the .init section. If that symbol is |
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41 | not defined however, then the .init section will not be used. |
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42 | |
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43 | Currently, only ELF and COFF are supported. It is likely however that |
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44 | ROSE could also be supported, if someone was willing to do the work to |
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45 | make whatever (small?) adaptations are needed. (Some work may be |
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46 | needed on the ROSE assembler and linker also.) |
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47 | |
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48 | This file must be compiled with gcc. */ |
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49 | |
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50 | /* It is incorrect to include config.h here, because this file is being |
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51 | compiled for the target, and hence definitions concerning only the host |
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52 | do not apply. */ |
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53 | |
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54 | #include "tm.h" |
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55 | #include "defaults.h" |
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56 | #include <stddef.h> |
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57 | #include "frame.h" |
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58 | |
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59 | /* Provide default definitions for the pseudo-ops used to switch to the |
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60 | .ctors and .dtors sections. |
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61 | |
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62 | Note that we want to give these sections the SHF_WRITE attribute |
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63 | because these sections will actually contain data (i.e. tables of |
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64 | addresses of functions in the current root executable or shared library |
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65 | file) and, in the case of a shared library, the relocatable addresses |
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66 | will have to be properly resolved/relocated (and then written into) by |
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67 | the dynamic linker when it actually attaches the given shared library |
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68 | to the executing process. (Note that on SVR4, you may wish to use the |
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69 | `-z text' option to the ELF linker, when building a shared library, as |
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70 | an additional check that you are doing everything right. But if you do |
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71 | use the `-z text' option when building a shared library, you will get |
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72 | errors unless the .ctors and .dtors sections are marked as writable |
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73 | via the SHF_WRITE attribute.) */ |
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74 | |
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75 | #ifndef CTORS_SECTION_ASM_OP |
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76 | #define CTORS_SECTION_ASM_OP ".section\t.ctors,\"aw\"" |
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77 | #endif |
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78 | #ifndef DTORS_SECTION_ASM_OP |
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79 | #define DTORS_SECTION_ASM_OP ".section\t.dtors,\"aw\"" |
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80 | #endif |
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81 | #if !defined (EH_FRAME_SECTION_ASM_OP) && defined (DWARF2_UNWIND_INFO) && defined(ASM_OUTPUT_SECTION_NAME) |
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82 | #define EH_FRAME_SECTION_ASM_OP ".section\t.eh_frame,\"aw\"" |
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83 | #endif |
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84 | |
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85 | #ifdef OBJECT_FORMAT_ELF |
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86 | |
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87 | /* Declare a pointer to void function type. */ |
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88 | typedef void (*func_ptr) (void); |
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89 | #define STATIC static |
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90 | |
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91 | #else /* OBJECT_FORMAT_ELF */ |
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92 | |
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93 | #include "gbl-ctors.h" |
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94 | |
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95 | #ifndef ON_EXIT |
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96 | #define ON_EXIT(a, b) |
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97 | #endif |
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98 | #define STATIC |
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99 | |
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100 | #endif /* OBJECT_FORMAT_ELF */ |
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101 | |
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102 | #ifdef CRT_BEGIN |
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103 | |
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104 | #ifdef INIT_SECTION_ASM_OP |
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105 | |
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106 | #ifdef OBJECT_FORMAT_ELF |
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107 | |
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108 | /* Run all the global destructors on exit from the program. */ |
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109 | |
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110 | /* Some systems place the number of pointers in the first word of the |
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111 | table. On SVR4 however, that word is -1. In all cases, the table is |
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112 | null-terminated. On SVR4, we start from the beginning of the list and |
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113 | invoke each per-compilation-unit destructor routine in order |
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114 | until we find that null. |
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115 | |
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116 | Note that this function MUST be static. There will be one of these |
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117 | functions in each root executable and one in each shared library, but |
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118 | although they all have the same code, each one is unique in that it |
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119 | refers to one particular associated `__DTOR_LIST__' which belongs to the |
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120 | same particular root executable or shared library file. |
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121 | |
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122 | On some systems, this routine is run more than once from the .fini, |
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123 | when exit is called recursively, so we arrange to remember where in |
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124 | the list we left off processing, and we resume at that point, |
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125 | should we be re-invoked. */ |
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126 | |
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127 | static char __EH_FRAME_BEGIN__[]; |
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128 | static func_ptr __DTOR_LIST__[]; |
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129 | static void |
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130 | __do_global_dtors_aux () |
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131 | { |
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132 | static func_ptr *p = __DTOR_LIST__ + 1; |
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133 | while (*p) |
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134 | { |
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135 | p++; |
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136 | (*(p-1)) (); |
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137 | } |
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138 | |
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139 | #ifdef EH_FRAME_SECTION_ASM_OP |
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140 | __deregister_frame_info (__EH_FRAME_BEGIN__); |
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141 | #endif |
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142 | } |
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143 | |
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144 | /* Stick a call to __do_global_dtors_aux into the .fini section. */ |
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145 | |
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146 | static void |
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147 | fini_dummy () |
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148 | { |
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149 | asm (FINI_SECTION_ASM_OP); |
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150 | __do_global_dtors_aux (); |
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151 | #ifdef FORCE_FINI_SECTION_ALIGN |
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152 | FORCE_FINI_SECTION_ALIGN; |
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153 | #endif |
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154 | asm (TEXT_SECTION_ASM_OP); |
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155 | } |
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156 | |
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157 | #ifdef EH_FRAME_SECTION_ASM_OP |
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158 | /* Stick a call to __register_frame_info into the .init section. For some |
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159 | reason calls with no arguments work more reliably in .init, so stick the |
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160 | call in another function. */ |
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161 | |
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162 | static void |
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163 | frame_dummy () |
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164 | { |
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165 | static struct object object; |
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166 | __register_frame_info (__EH_FRAME_BEGIN__, &object); |
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167 | } |
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168 | |
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169 | static void |
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170 | init_dummy () |
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171 | { |
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172 | asm (INIT_SECTION_ASM_OP); |
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173 | frame_dummy (); |
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174 | #ifdef FORCE_INIT_SECTION_ALIGN |
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175 | FORCE_INIT_SECTION_ALIGN; |
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176 | #endif |
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177 | asm (TEXT_SECTION_ASM_OP); |
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178 | } |
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179 | #endif /* EH_FRAME_SECTION_ASM_OP */ |
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180 | |
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181 | #else /* OBJECT_FORMAT_ELF */ |
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182 | |
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183 | /* The function __do_global_ctors_aux is compiled twice (once in crtbegin.o |
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184 | and once in crtend.o). It must be declared static to avoid a link |
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185 | error. Here, we define __do_global_ctors as an externally callable |
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186 | function. It is externally callable so that __main can invoke it when |
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187 | INVOKE__main is defined. This has the additional effect of forcing cc1 |
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188 | to switch to the .text section. */ |
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189 | |
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190 | static void __do_global_ctors_aux (); |
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191 | void __do_global_ctors () |
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192 | { |
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193 | #ifdef INVOKE__main /* If __main won't actually call __do_global_ctors |
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194 | then it doesn't matter what's inside the function. |
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195 | The inside of __do_global_ctors_aux is called |
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196 | automatically in that case. |
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197 | And the Alliant fx2800 linker crashes |
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198 | on this reference. So prevent the crash. */ |
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199 | __do_global_ctors_aux (); |
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200 | #endif |
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201 | } |
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202 | |
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203 | asm (INIT_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */ |
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204 | |
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205 | /* On some svr4 systems, the initial .init section preamble code provided in |
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206 | crti.o may do something, such as bump the stack, which we have to |
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207 | undo before we reach the function prologue code for __do_global_ctors |
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208 | (directly below). For such systems, define the macro INIT_SECTION_PREAMBLE |
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209 | to expand into the code needed to undo the actions of the crti.o file. */ |
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210 | |
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211 | #ifdef INIT_SECTION_PREAMBLE |
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212 | INIT_SECTION_PREAMBLE; |
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213 | #endif |
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214 | |
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215 | /* A routine to invoke all of the global constructors upon entry to the |
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216 | program. We put this into the .init section (for systems that have |
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217 | such a thing) so that we can properly perform the construction of |
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218 | file-scope static-storage C++ objects within shared libraries. */ |
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219 | |
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220 | static void |
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221 | __do_global_ctors_aux () /* prologue goes in .init section */ |
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222 | { |
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223 | #ifdef FORCE_INIT_SECTION_ALIGN |
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224 | FORCE_INIT_SECTION_ALIGN; /* Explicit align before switch to .text */ |
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225 | #endif |
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226 | asm (TEXT_SECTION_ASM_OP); /* don't put epilogue and body in .init */ |
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227 | DO_GLOBAL_CTORS_BODY; |
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228 | ON_EXIT (__do_global_dtors, 0); |
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229 | } |
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230 | |
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231 | #endif /* OBJECT_FORMAT_ELF */ |
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232 | |
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233 | #else /* defined(INIT_SECTION_ASM_OP) */ |
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234 | |
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235 | #ifdef HAS_INIT_SECTION |
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236 | /* This case is used by the Irix 6 port, which supports named sections but |
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237 | not an SVR4-style .fini section. __do_global_dtors can be non-static |
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238 | in this case because we protect it with -hidden_symbol. */ |
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239 | |
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240 | static char __EH_FRAME_BEGIN__[]; |
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241 | static func_ptr __DTOR_LIST__[]; |
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242 | void |
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243 | __do_global_dtors () |
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244 | { |
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245 | func_ptr *p; |
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246 | for (p = __DTOR_LIST__ + 1; *p; p++) |
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247 | (*p) (); |
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248 | |
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249 | #ifdef EH_FRAME_SECTION_ASM_OP |
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250 | __deregister_frame_info (__EH_FRAME_BEGIN__); |
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251 | #endif |
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252 | } |
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253 | |
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254 | #ifdef EH_FRAME_SECTION_ASM_OP |
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255 | /* Define a function here to call __register_frame. crtend.o is linked in |
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256 | after libgcc.a, and hence can't call libgcc.a functions directly. That |
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257 | can lead to unresolved function references. */ |
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258 | void |
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259 | __frame_dummy () |
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260 | { |
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261 | static struct object object; |
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262 | __register_frame_info (__EH_FRAME_BEGIN__, &object); |
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263 | } |
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264 | #endif |
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265 | #endif |
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266 | |
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267 | #endif /* defined(INIT_SECTION_ASM_OP) */ |
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268 | |
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269 | /* Force cc1 to switch to .data section. */ |
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270 | static func_ptr force_to_data[0] = { }; |
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271 | |
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272 | /* NOTE: In order to be able to support SVR4 shared libraries, we arrange |
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273 | to have one set of symbols { __CTOR_LIST__, __DTOR_LIST__, __CTOR_END__, |
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274 | __DTOR_END__ } per root executable and also one set of these symbols |
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275 | per shared library. So in any given whole process image, we may have |
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276 | multiple definitions of each of these symbols. In order to prevent |
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277 | these definitions from conflicting with one another, and in order to |
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278 | ensure that the proper lists are used for the initialization/finalization |
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279 | of each individual shared library (respectively), we give these symbols |
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280 | only internal (i.e. `static') linkage, and we also make it a point to |
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281 | refer to only the __CTOR_END__ symbol in crtend.o and the __DTOR_LIST__ |
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282 | symbol in crtbegin.o, where they are defined. */ |
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283 | |
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284 | /* The -1 is a flag to __do_global_[cd]tors |
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285 | indicating that this table does not start with a count of elements. */ |
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286 | #ifdef CTOR_LIST_BEGIN |
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287 | CTOR_LIST_BEGIN; |
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288 | #else |
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289 | asm (CTORS_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */ |
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290 | STATIC func_ptr __CTOR_LIST__[1] = { (func_ptr) (-1) }; |
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291 | #endif |
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292 | |
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293 | #ifdef DTOR_LIST_BEGIN |
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294 | DTOR_LIST_BEGIN; |
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295 | #else |
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296 | asm (DTORS_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */ |
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297 | STATIC func_ptr __DTOR_LIST__[1] = { (func_ptr) (-1) }; |
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298 | #endif |
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299 | |
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300 | #ifdef EH_FRAME_SECTION_ASM_OP |
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301 | /* Stick a label at the beginning of the frame unwind info so we can register |
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302 | and deregister it with the exception handling library code. */ |
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303 | |
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304 | asm (EH_FRAME_SECTION_ASM_OP); |
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305 | #ifdef INIT_SECTION_ASM_OP |
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306 | STATIC |
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307 | #endif |
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308 | char __EH_FRAME_BEGIN__[] = { }; |
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309 | #endif /* EH_FRAME_SECTION_ASM_OP */ |
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310 | |
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311 | #endif /* defined(CRT_BEGIN) */ |
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312 | |
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313 | #ifdef CRT_END |
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314 | |
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315 | #ifdef INIT_SECTION_ASM_OP |
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316 | |
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317 | #ifdef OBJECT_FORMAT_ELF |
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318 | |
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319 | static func_ptr __CTOR_END__[]; |
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320 | static void |
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321 | __do_global_ctors_aux () |
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322 | { |
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323 | func_ptr *p; |
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324 | for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--) |
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325 | (*p) (); |
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326 | } |
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327 | |
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328 | /* Stick a call to __do_global_ctors_aux into the .init section. */ |
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329 | |
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330 | static void |
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331 | init_dummy () |
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332 | { |
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333 | asm (INIT_SECTION_ASM_OP); |
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334 | __do_global_ctors_aux (); |
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335 | #ifdef FORCE_INIT_SECTION_ALIGN |
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336 | FORCE_INIT_SECTION_ALIGN; |
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337 | #endif |
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338 | asm (TEXT_SECTION_ASM_OP); |
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339 | |
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340 | /* This is a kludge. The i386 GNU/Linux dynamic linker needs ___brk_addr, |
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341 | __environ and atexit (). We have to make sure they are in the .dynsym |
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342 | section. We accomplish it by making a dummy call here. This |
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343 | code is never reached. */ |
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344 | |
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345 | #if defined(__linux__) && defined(__PIC__) && defined(__i386__) |
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346 | { |
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347 | extern void *___brk_addr; |
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348 | extern char **__environ; |
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349 | |
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350 | ___brk_addr = __environ; |
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351 | atexit (); |
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352 | } |
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353 | #endif |
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354 | } |
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355 | |
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356 | #else /* OBJECT_FORMAT_ELF */ |
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357 | |
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358 | /* Stick the real initialization code, followed by a normal sort of |
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359 | function epilogue at the very end of the .init section for this |
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360 | entire root executable file or for this entire shared library file. |
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361 | |
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362 | Note that we use some tricks here to get *just* the body and just |
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363 | a function epilogue (but no function prologue) into the .init |
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364 | section of the crtend.o file. Specifically, we switch to the .text |
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365 | section, start to define a function, and then we switch to the .init |
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366 | section just before the body code. |
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367 | |
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368 | Earlier on, we put the corresponding function prologue into the .init |
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369 | section of the crtbegin.o file (which will be linked in first). |
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370 | |
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371 | Note that we want to invoke all constructors for C++ file-scope static- |
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372 | storage objects AFTER any other possible initialization actions which |
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373 | may be performed by the code in the .init section contributions made by |
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374 | other libraries, etc. That's because those other initializations may |
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375 | include setup operations for very primitive things (e.g. initializing |
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376 | the state of the floating-point coprocessor, etc.) which should be done |
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377 | before we start to execute any of the user's code. */ |
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378 | |
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379 | static void |
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380 | __do_global_ctors_aux () /* prologue goes in .text section */ |
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381 | { |
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382 | asm (INIT_SECTION_ASM_OP); |
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383 | DO_GLOBAL_CTORS_BODY; |
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384 | ON_EXIT (__do_global_dtors, 0); |
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385 | } /* epilogue and body go in .init section */ |
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386 | |
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387 | #ifdef FORCE_INIT_SECTION_ALIGN |
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388 | FORCE_INIT_SECTION_ALIGN; |
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389 | #endif |
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390 | |
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391 | asm (TEXT_SECTION_ASM_OP); |
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392 | |
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393 | #endif /* OBJECT_FORMAT_ELF */ |
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394 | |
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395 | #else /* defined(INIT_SECTION_ASM_OP) */ |
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396 | |
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397 | #ifdef HAS_INIT_SECTION |
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398 | /* This case is used by the Irix 6 port, which supports named sections but |
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399 | not an SVR4-style .init section. __do_global_ctors can be non-static |
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400 | in this case because we protect it with -hidden_symbol. */ |
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401 | static func_ptr __CTOR_END__[]; |
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402 | void |
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403 | __do_global_ctors () |
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404 | { |
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405 | func_ptr *p; |
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406 | #ifdef EH_FRAME_SECTION_ASM_OP |
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407 | __frame_dummy (); |
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408 | #endif |
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409 | for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--) |
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410 | (*p) (); |
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411 | } |
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412 | #endif |
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413 | |
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414 | #endif /* defined(INIT_SECTION_ASM_OP) */ |
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415 | |
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416 | /* Force cc1 to switch to .data section. */ |
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417 | static func_ptr force_to_data[0] = { }; |
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418 | |
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419 | /* Put a word containing zero at the end of each of our two lists of function |
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420 | addresses. Note that the words defined here go into the .ctors and .dtors |
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421 | sections of the crtend.o file, and since that file is always linked in |
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422 | last, these words naturally end up at the very ends of the two lists |
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423 | contained in these two sections. */ |
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424 | |
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425 | #ifdef CTOR_LIST_END |
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426 | CTOR_LIST_END; |
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427 | #else |
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428 | asm (CTORS_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */ |
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429 | STATIC func_ptr __CTOR_END__[1] = { (func_ptr) 0 }; |
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430 | #endif |
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431 | |
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432 | #ifdef DTOR_LIST_END |
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433 | DTOR_LIST_END; |
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434 | #else |
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435 | asm (DTORS_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */ |
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436 | STATIC func_ptr __DTOR_END__[1] = { (func_ptr) 0 }; |
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437 | #endif |
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438 | |
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439 | #ifdef EH_FRAME_SECTION_ASM_OP |
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440 | /* Terminate the frame unwind info section with a 4byte 0 as a sentinel; |
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441 | this would be the 'length' field in a real FDE. */ |
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442 | |
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443 | typedef unsigned int ui32 __attribute__ ((mode (SI))); |
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444 | asm (EH_FRAME_SECTION_ASM_OP); |
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445 | STATIC ui32 __FRAME_END__[] = { 0 }; |
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446 | #endif /* EH_FRAME_SECTION */ |
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447 | |
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448 | #endif /* defined(CRT_END) */ |
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