1 /* Support macros for making weak and strong aliases for symbols, 2 and for using symbol sets and linker warnings with GNU ld. 3 Copyright (C) 1995,1996,1997,1998,2000,2001 Free Software Foundation, Inc. 4 This file is part of the GNU C Library. 5 6 The GNU C Library is free software; you can redistribute it and/or 7 modify it under the terms of the GNU Lesser General Public 8 License as published by the Free Software Foundation; either 9 version 2.1 of the License, or (at your option) any later version. 10 11 The GNU C Library is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 Lesser General Public License for more details. 15 16 You should have received a copy of the GNU Lesser General Public 17 License along with the GNU C Library; if not, write to the Free 18 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 19 02111-1307 USA. */ 20 21 #ifndef _LIBC_SYMBOLS_H 22 #define _LIBC_SYMBOLS_H 1 23 24 /* This file's macros are included implicitly in the compilation of every 25 file in the C library by -imacros. 26 27 We include config.h which is generated by configure. 28 It should define for us the following symbols: 29 30 * HAVE_ASM_SET_DIRECTIVE if we have `.set B, A' instead of `A = B'. 31 * ASM_GLOBAL_DIRECTIVE with `.globl' or `.global'. 32 * HAVE_GNU_LD if using GNU ld, with support for weak symbols in a.out, 33 and for symbol set and warning messages extensions in a.out and ELF. 34 * HAVE_ELF if using ELF, which supports weak symbols using `.weak'. 35 * HAVE_ASM_WEAK_DIRECTIVE if we have weak symbols using `.weak'. 36 * HAVE_ASM_WEAKEXT_DIRECTIVE if we have weak symbols using `.weakext'. 37 38 */ 39 40 /* This is defined for the compilation of all C library code. features.h 41 tests this to avoid inclusion of stubs.h while compiling the library, 42 before stubs.h has been generated. Some library code that is shared 43 with other packages also tests this symbol to see if it is being 44 compiled as part of the C library. We must define this before including 45 config.h, because it makes some definitions conditional on whether libc 46 itself is being compiled, or just some generator program. */ 47 #define _LIBC 1 48 49 /* Enable declarations of GNU extensions, since we are compiling them. */ 50 #define _GNU_SOURCE 1 51 /* And we also need the data for the reentrant functions. */ 52 #define _REENTRANT 1 53 54 #include <config.h> 55 56 /* The symbols in all the user (non-_) macros are C symbols. 57 HAVE_GNU_LD without HAVE_ELF implies a.out. */ 58 59 #if defined HAVE_ASM_WEAK_DIRECTIVE || defined HAVE_ASM_WEAKEXT_DIRECTIVE 60 # define HAVE_WEAK_SYMBOLS 61 #endif 62 63 #ifndef __SYMBOL_PREFIX 64 # ifdef NO_UNDERSCORES 65 # define __SYMBOL_PREFIX 66 # else 67 # define __SYMBOL_PREFIX "_" 68 # endif 69 #endif 70 71 #ifndef C_SYMBOL_NAME 72 # ifdef NO_UNDERSCORES 73 # define C_SYMBOL_NAME(name) name 74 # else 75 # define C_SYMBOL_NAME(name) _##name 76 # endif 77 #endif 78 79 #ifndef ASM_LINE_SEP 80 # define ASM_LINE_SEP ; 81 #endif 82 83 #ifndef C_SYMBOL_DOT_NAME 84 # define C_SYMBOL_DOT_NAME(name) .##name 85 #endif 86 87 #ifndef __ASSEMBLER__ 88 /* GCC understands weak symbols and aliases; use its interface where 89 possible, instead of embedded assembly language. */ 90 91 /* Define ALIASNAME as a strong alias for NAME. */ 92 # define strong_alias(name, aliasname) _strong_alias(name, aliasname) 93 # define _strong_alias(name, aliasname) \ 94 extern __typeof (name) aliasname __attribute__ ((alias (#name))); 95 96 /* This comes between the return type and function name in 97 a function definition to make that definition weak. */ 98 # define weak_function __attribute__ ((weak)) 99 # define weak_const_function __attribute__ ((weak, __const__)) 100 101 # ifdef HAVE_WEAK_SYMBOLS 102 103 /* Define ALIASNAME as a weak alias for NAME. 104 If weak aliases are not available, this defines a strong alias. */ 105 # define weak_alias(name, aliasname) _weak_alias (name, aliasname) 106 # define _weak_alias(name, aliasname) \ 107 extern __typeof (name) aliasname __attribute__ ((weak, alias (#name))); 108 109 /* Declare SYMBOL as weak undefined symbol (resolved to 0 if not defined). */ 110 # define weak_extern(symbol) _weak_extern (symbol) 111 # ifdef HAVE_ASM_WEAKEXT_DIRECTIVE 112 # define _weak_extern(symbol) asm (".weakext " __SYMBOL_PREFIX #symbol); 113 # else 114 # define _weak_extern(symbol) asm (".weak " __SYMBOL_PREFIX #symbol); 115 # endif 116 117 # else 118 119 # define weak_alias(name, aliasname) strong_alias(name, aliasname) 120 # define weak_extern(symbol) /* Nothing. */ 121 122 # endif 123 124 #else /* __ASSEMBLER__ */ 125 126 # ifdef HAVE_ASM_SET_DIRECTIVE 127 # define strong_alias(original, alias) \ 128 ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP \ 129 .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original) 130 # else 131 # ifdef HAVE_ASM_GLOBAL_DOT_NAME 132 # define strong_alias(original, alias) \ 133 ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP \ 134 C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) ASM_LINE_SEP \ 135 ASM_GLOBAL_DIRECTIVE C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP \ 136 C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original) 137 # else 138 # define strong_alias(original, alias) \ 139 ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP \ 140 C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) 141 # endif 142 # endif 143 144 # ifdef HAVE_WEAK_SYMBOLS 145 # ifdef HAVE_ASM_WEAKEXT_DIRECTIVE 146 # define weak_alias(original, alias) \ 147 .weakext C_SYMBOL_NAME (alias), C_SYMBOL_NAME (original) 148 # define weak_extern(symbol) \ 149 .weakext C_SYMBOL_NAME (symbol) 150 151 # else /* ! HAVE_ASM_WEAKEXT_DIRECTIVE */ 152 153 # ifdef HAVE_ASM_GLOBAL_DOT_NAME 154 # define weak_alias(original, alias) \ 155 .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP \ 156 C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) ASM_LINE_SEP \ 157 ASM_GLOBAL_DIRECTIVE C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP \ 158 C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original) 159 # else 160 # define weak_alias(original, alias) \ 161 .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP \ 162 C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) 163 # endif 164 165 # define weak_extern(symbol) \ 166 .weak C_SYMBOL_NAME (symbol) 167 168 # endif /* ! HAVE_ASM_WEAKEXT_DIRECTIVE */ 169 170 # else /* ! HAVE_WEAK_SYMBOLS */ 171 172 # define weak_alias(original, alias) strong_alias(original, alias) 173 # define weak_extern(symbol) /* Nothing */ 174 # endif /* ! HAVE_WEAK_SYMBOLS */ 175 176 #endif /* __ASSEMBLER__ */ 177 178 /* On some platforms we can make internal function calls (i.e., calls of 179 functions not exported) a bit faster by using a different calling 180 convention. */ 181 #ifndef internal_function 182 # define internal_function /* empty */ 183 #endif 184 185 /* Prepare for the case that `__builtin_expect' is not available. */ 186 #ifndef HAVE_BUILTIN_EXPECT 187 # define __builtin_expect(expr, val) (expr) 188 #endif 189 190 /* Determine the return address. */ 191 #define RETURN_ADDRESS(nr) \ 192 __builtin_extract_return_addr (__builtin_return_address (nr)) 193 194 /* When a reference to SYMBOL is encountered, the linker will emit a 195 warning message MSG. */ 196 #ifdef HAVE_GNU_LD 197 # ifdef HAVE_ELF 198 199 /* We want the .gnu.warning.SYMBOL section to be unallocated. */ 200 # ifdef HAVE_ASM_PREVIOUS_DIRECTIVE 201 # define __make_section_unallocated(section_string) \ 202 asm (".section " section_string "\n\t.previous"); 203 # elif defined HAVE_ASM_POPSECTION_DIRECTIVE 204 # define __make_section_unallocated(section_string) \ 205 asm (".pushsection " section_string "\n\t.popsection"); 206 # else 207 # define __make_section_unallocated(section_string) 208 # endif 209 210 /* Tacking on "\n\t#" to the section name makes gcc put it's bogus 211 section attributes on what looks like a comment to the assembler. */ 212 # ifdef HAVE_SECTION_QUOTES 213 # define link_warning(symbol, msg) \ 214 __make_section_unallocated (".gnu.warning." #symbol) \ 215 static const char __evoke_link_warning_##symbol[] \ 216 __attribute__ ((section (".gnu.warning." #symbol "\"\n\t#\""))) = msg; 217 # else 218 # define link_warning(symbol, msg) \ 219 __make_section_unallocated (".gnu.warning." #symbol) \ 220 static const char __evoke_link_warning_##symbol[] \ 221 __attribute__ ((section (".gnu.warning." #symbol "\n\t#"))) = msg; 222 # endif 223 # else /* Not ELF: a.out */ 224 # ifdef HAVE_XCOFF 225 /* XCOFF does not support .stabs. 226 The native aix linker will remove the .stab and .stabstr sections 227 The gnu linker will have a fatal error if there is a relocation for 228 symbol in the .stab section. Silently disable this macro. */ 229 # define link_warning(symbol, msg) 230 # else 231 # define link_warning(symbol, msg) \ 232 asm (".stabs \"" msg "\",30,0,0,0\n\t" \ 233 ".stabs \"" __SYMBOL_PREFIX #symbol "\",1,0,0,0\n"); 234 # endif /* XCOFF */ 235 # endif 236 #else 237 /* We will never be heard; they will all die horribly. */ 238 # define link_warning(symbol, msg) 239 #endif 240 241 /* A canned warning for sysdeps/stub functions. */ 242 #define stub_warning(name) \ 243 link_warning (name, \ 244 "warning: " #name " is not implemented and will always fail") 245 246 /* 247 248 */ 249 250 #ifdef HAVE_GNU_LD 251 252 /* Symbol set support macros. */ 253 254 # ifdef HAVE_ELF 255 256 /* Make SYMBOL, which is in the text segment, an element of SET. */ 257 # define text_set_element(set, symbol) _elf_set_element(set, symbol) 258 /* Make SYMBOL, which is in the data segment, an element of SET. */ 259 # define data_set_element(set, symbol) _elf_set_element(set, symbol) 260 /* Make SYMBOL, which is in the bss segment, an element of SET. */ 261 # define bss_set_element(set, symbol) _elf_set_element(set, symbol) 262 263 /* These are all done the same way in ELF. 264 There is a new section created for each set. */ 265 # ifdef SHARED 266 /* When building a shared library, make the set section writable, 267 because it will need to be relocated at run time anyway. */ 268 # define _elf_set_element(set, symbol) \ 269 static const void *__elf_set_##set##_element_##symbol##__ \ 270 __attribute__ ((unused, section (#set))) = &(symbol) 271 # else 272 # define _elf_set_element(set, symbol) \ 273 static const void *const __elf_set_##set##_element_##symbol##__ \ 274 __attribute__ ((unused, section (#set))) = &(symbol) 275 # endif 276 277 /* Define SET as a symbol set. This may be required (it is in a.out) to 278 be able to use the set's contents. */ 279 # define symbol_set_define(set) symbol_set_declare(set) 280 281 /* Declare SET for use in this module, if defined in another module. */ 282 # define symbol_set_declare(set) \ 283 extern void *const __start_##set __attribute__ ((__weak__)); \ 284 extern void *const __stop_##set __attribute__ ((__weak__)); \ 285 weak_extern (__start_##set) weak_extern (__stop_##set) 286 287 /* Return a pointer (void *const *) to the first element of SET. */ 288 # define symbol_set_first_element(set) (&__start_##set) 289 290 /* Return true iff PTR (a void *const *) has been incremented 291 past the last element in SET. */ 292 # define symbol_set_end_p(set, ptr) ((ptr) >= &__stop_##set) 293 294 # else /* Not ELF: a.out. */ 295 296 # ifdef HAVE_XCOFF 297 /* XCOFF does not support .stabs. 298 The native aix linker will remove the .stab and .stabstr sections 299 The gnu linker will have a fatal error if there is a relocation for 300 symbol in the .stab section. Silently disable these macros. */ 301 # define text_set_element(set, symbol) 302 # define data_set_element(set, symbol) 303 # define bss_set_element(set, symbol) 304 # else 305 # define text_set_element(set, symbol) \ 306 asm (".stabs \"" __SYMBOL_PREFIX #set "\",23,0,0," __SYMBOL_PREFIX #symbol) 307 # define data_set_element(set, symbol) \ 308 asm (".stabs \"" __SYMBOL_PREFIX #set "\",25,0,0," __SYMBOL_PREFIX #symbol) 309 # define bss_set_element(set, symbol) ?error Must use initialized data. 310 # endif /* XCOFF */ 311 # define symbol_set_define(set) void *const (set)[1]; 312 # define symbol_set_declare(set) extern void *const (set)[1]; 313 314 # define symbol_set_first_element(set) &(set)[1] 315 # define symbol_set_end_p(set, ptr) (*(ptr) == 0) 316 317 # endif /* ELF. */ 318 #else 319 /* We cannot do anything in generial. */ 320 # define text_set_element(set, symbol) asm ("") 321 # define data_set_element(set, symbol) asm ("") 322 # define bss_set_element(set, symbol) asm ("") 323 # define symbol_set_define(set) void *const (set)[1]; 324 # define symbol_set_declare(set) extern void *const (set)[1]; 325 326 # define symbol_set_first_element(set) &(set)[1] 327 # define symbol_set_end_p(set, ptr) (*(ptr) == 0) 328 #endif /* Have GNU ld. */ 329 330 #if DO_VERSIONING 331 # define symbol_version(real, name, version) \ 332 _symbol_version(real, name, version) 333 # define default_symbol_version(real, name, version) \ 334 _default_symbol_version(real, name, version) 335 # ifdef __ASSEMBLER__ 336 # define _symbol_version(real, name, version) \ 337 .symver real, name##@##version 338 # define _default_symbol_version(real, name, version) \ 339 .symver real, name##@##@##version 340 # else 341 # define _symbol_version(real, name, version) \ 342 __asm__ (".symver " #real "," #name "@" #version) 343 # define _default_symbol_version(real, name, version) \ 344 __asm__ (".symver " #real "," #name "@@" #version) 345 # endif 346 #else 347 # define symbol_version(real, name, version) 348 # define default_symbol_version(real, name, version) \ 349 strong_alias(real, name) 350 #endif 351 352 #endif /* libc-symbols.h */ 353