include/libc-symbols.h

   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) 1995-1998,2000,2001,2002 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    * ASM_TYPE_DIRECTIVE_PREFIX with `@' or `#' or whatever for .type,
  33      or leave it undefined if there is no .type directive.
  34    * HAVE_GNU_LD if using GNU ld, with support for weak symbols in a.out,
  35    and for symbol set and warning messages extensions in a.out and ELF.
  36    * HAVE_ELF if using ELF, which supports weak symbols using `.weak'.
  37    * HAVE_ASM_WEAK_DIRECTIVE if we have weak symbols using `.weak'.
  38    * HAVE_ASM_WEAKEXT_DIRECTIVE if we have weak symbols using `.weakext'.
  39
  40    */
  41
  42 /* This is defined for the compilation of all C library code.  features.h
  43    tests this to avoid inclusion of stubs.h while compiling the library,
  44    before stubs.h has been generated.  Some library code that is shared
  45    with other packages also tests this symbol to see if it is being
  46    compiled as part of the C library.  We must define this before including
  47    config.h, because it makes some definitions conditional on whether libc
  48    itself is being compiled, or just some generator program.  */
  49 #define _LIBC   1
  50
  51 /* Enable declarations of GNU extensions, since we are compiling them.  */
  52 #define _GNU_SOURCE     1
  53 /* And we also need the data for the reentrant functions.  */
  54 #define _REENTRANT      1
  55
  56 #include <config.h>
  57
  58 /* The symbols in all the user (non-_) macros are C symbols.
  59    HAVE_GNU_LD without HAVE_ELF implies a.out.  */
  60
  61 #if defined HAVE_ASM_WEAK_DIRECTIVE || defined HAVE_ASM_WEAKEXT_DIRECTIVE
  62 # define HAVE_WEAK_SYMBOLS
  63 #endif
  64
  65 #ifndef __SYMBOL_PREFIX
  66 # ifdef NO_UNDERSCORES
  67 #  define __SYMBOL_PREFIX
  68 # else
  69 #  define __SYMBOL_PREFIX "_"
  70 # endif
  71 #endif
  72
  73 #ifndef C_SYMBOL_NAME
  74 # ifdef NO_UNDERSCORES
  75 #  define C_SYMBOL_NAME(name) name
  76 # else
  77 #  define C_SYMBOL_NAME(name) _##name
  78 # endif
  79 #endif
  80
  81 #ifndef ASM_LINE_SEP
  82 # define ASM_LINE_SEP ;
  83 #endif
  84
  85 #ifdef HAVE_ASM_GLOBAL_DOT_NAME
  86 # ifndef C_SYMBOL_DOT_NAME
  87 #  if defined __GNUC__ && defined __GNUC_MINOR__ \
  88       && (__GNUC__ << 16) + __GNUC_MINOR__ >= (3 << 16) + 1
  89 #   define C_SYMBOL_DOT_NAME(name) .name
  90 #  else
  91 #   define C_SYMBOL_DOT_NAME(name) .##name
  92 #  endif
  93 # endif
  94 #endif
  95
  96 #ifndef __ASSEMBLER__
  97 /* GCC understands weak symbols and aliases; use its interface where
  98    possible, instead of embedded assembly language.  */
  99
 100 /* Define ALIASNAME as a strong alias for NAME.  */
 101 # define strong_alias(name, aliasname) _strong_alias(name, aliasname)
 102 # define _strong_alias(name, aliasname) \
 103   extern __typeof (name) aliasname __attribute__ ((alias (#name)));
 104
 105 /* This comes between the return type and function name in
 106    a function definition to make that definition weak.  */
 107 # define weak_function __attribute__ ((weak))
 108 # define weak_const_function __attribute__ ((weak, __const__))
 109
 110 # ifdef HAVE_WEAK_SYMBOLS
 111
 112 /* Define ALIASNAME as a weak alias for NAME.
 113    If weak aliases are not available, this defines a strong alias.  */
 114 #  define weak_alias(name, aliasname) _weak_alias (name, aliasname)
 115 #  define _weak_alias(name, aliasname) \
 116   extern __typeof (name) aliasname __attribute__ ((weak, alias (#name)));
 117
 118 /* Declare SYMBOL as weak undefined symbol (resolved to 0 if not defined).  */
 119 #  define weak_extern(symbol) _weak_extern (symbol)
 120 #  ifdef HAVE_ASM_WEAKEXT_DIRECTIVE
 121 #   ifdef HAVE_ASM_GLOBAL_DOT_NAME
 122 #    define _weak_extern(symbol) \
 123         asm (".weakext " __SYMBOL_PREFIX #symbol "\n\t" \
 124              ".weakext ." __SYMBOL_PREFIX #symbol);
 125 #   else
 126 #    define _weak_extern(symbol) asm (".weakext " __SYMBOL_PREFIX #symbol);
 127 #   endif
 128 #  else
 129 #   ifdef HAVE_ASM_GLOBAL_DOT_NAME
 130 #    define _weak_extern(symbol) \
 131         asm (".weak " __SYMBOL_PREFIX #symbol "\n\t"    \
 132              ".weak ." __SYMBOL_PREFIX #symbol);
 133 #   else
 134 #    define _weak_extern(symbol) asm (".weak " __SYMBOL_PREFIX #symbol);
 135 #   endif
 136 #  endif
 137
 138 # else
 139
 140 #  define weak_alias(name, aliasname) strong_alias(name, aliasname)
 141 #  define weak_extern(symbol) /* Nothing. */
 142
 143 # endif
 144
 145 #else /* __ASSEMBLER__ */
 146
 147 # ifdef HAVE_ASM_SET_DIRECTIVE
 148 #  ifdef HAVE_ASM_GLOBAL_DOT_NAME
 149 #   define strong_alias(original, alias)                                \
 150   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP               \
 151   .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original) ASM_LINE_SEP      \
 152   ASM_GLOBAL_DIRECTIVE C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP           \
 153   .set C_SYMBOL_DOT_NAME (alias),C_SYMBOL_DOT_NAME (original)
 154 #   define strong_data_alias(original, alias)                           \
 155   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP               \
 156   .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original)
 157 #  else
 158 #   define strong_alias(original, alias)                                \
 159   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP               \
 160   .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original)
 161 #   define strong_data_alias(original, alias) strong_alias(original, alias)
 162 #  endif
 163 # else
 164 #  ifdef HAVE_ASM_GLOBAL_DOT_NAME
 165 #   define strong_alias(original, alias)                                \
 166   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP               \
 167   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) ASM_LINE_SEP         \
 168   ASM_GLOBAL_DIRECTIVE C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP           \
 169   C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original)
 170 #   define strong_data_alias(original, alias)                           \
 171   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP               \
 172   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 173 #  else
 174 #   define strong_alias(original, alias)                                \
 175   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP               \
 176   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 177 #   define strong_data_alias(original, alias) strong_alias(original, alias)
 178 #  endif
 179 # endif
 180
 181 # ifdef HAVE_WEAK_SYMBOLS
 182 #  ifdef HAVE_ASM_WEAKEXT_DIRECTIVE
 183 #   ifdef HAVE_ASM_GLOBAL_DOT_NAME
 184 #    define weak_alias(original, alias)                                 \
 185   .weakext C_SYMBOL_NAME (alias), C_SYMBOL_NAME (original) ASM_LINE_SEP \
 186   .weakext C_SYMBOL_DOT_NAME (alias), C_SYMBOL_DOT_NAME (original)
 187 #   else
 188 #    define weak_alias(original, alias)                                 \
 189   .weakext C_SYMBOL_NAME (alias), C_SYMBOL_NAME (original)
 190 #   endif
 191 #   define weak_extern(symbol)                                          \
 192   .weakext C_SYMBOL_NAME (symbol)
 193
 194 #  else /* ! HAVE_ASM_WEAKEXT_DIRECTIVE */
 195
 196 #   ifdef HAVE_ASM_GLOBAL_DOT_NAME
 197 #    define weak_alias(original, alias)                                 \
 198   .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP                              \
 199   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) ASM_LINE_SEP         \
 200   .weak C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP                          \
 201   C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original)
 202 #   else
 203 #    define weak_alias(original, alias)                                 \
 204   .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP                              \
 205   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 206 #   endif
 207
 208 #   define weak_extern(symbol)                                          \
 209   .weak C_SYMBOL_NAME (symbol)
 210
 211 #  endif /* ! HAVE_ASM_WEAKEXT_DIRECTIVE */
 212
 213 # else /* ! HAVE_WEAK_SYMBOLS */
 214
 215 #  define weak_alias(original, alias) strong_alias(original, alias)
 216 #  define weak_extern(symbol) /* Nothing */
 217 # endif /* ! HAVE_WEAK_SYMBOLS */
 218
 219 #endif /* __ASSEMBLER__ */
 220
 221 /* On some platforms we can make internal function calls (i.e., calls of
 222    functions not exported) a bit faster by using a different calling
 223    convention.  */
 224 #ifndef internal_function
 225 # define internal_function      /* empty */
 226 #endif
 227
 228 /* Prepare for the case that `__builtin_expect' is not available.  */
 229 #ifndef HAVE_BUILTIN_EXPECT
 230 # define __builtin_expect(expr, val) (expr)
 231 #endif
 232
 233 /* Determine the return address.  */
 234 #define RETURN_ADDRESS(nr) \
 235   __builtin_extract_return_addr (__builtin_return_address (nr))
 236
 237 /* When a reference to SYMBOL is encountered, the linker will emit a
 238    warning message MSG.  */
 239 #ifdef HAVE_GNU_LD
 240 # ifdef HAVE_ELF
 241
 242 /* We want the .gnu.warning.SYMBOL section to be unallocated.  */
 243 #  ifdef HAVE_ASM_PREVIOUS_DIRECTIVE
 244 #   define __make_section_unallocated(section_string)   \
 245   asm (".section " section_string "\n\t.previous");
 246 #  elif defined HAVE_ASM_POPSECTION_DIRECTIVE
 247 #   define __make_section_unallocated(section_string)   \
 248   asm (".pushsection " section_string "\n\t.popsection");
 249 #  else
 250 #   define __make_section_unallocated(section_string)
 251 #  endif
 252
 253 /* Tacking on "\n\t#" to the section name makes gcc put it's bogus
 254    section attributes on what looks like a comment to the assembler.  */
 255 #  ifdef HAVE_SECTION_QUOTES
 256 #   define __sec_comment "\"\n\t#\""
 257 #  else
 258 #   define __sec_comment "\n\t#"
 259 #  endif
 260 #  define link_warning(symbol, msg) \
 261   __make_section_unallocated (".gnu.warning." #symbol) \
 262   static const char __evoke_link_warning_##symbol[]     \
 263     __attribute__ ((unused, section (".gnu.warning." #symbol __sec_comment))) \
 264     = msg;
 265 #  define libc_freeres_ptr(decl) \
 266   __make_section_unallocated ("__libc_freeres_ptrs, \"aw\", @nobits") \
 267   decl __attribute__ ((section ("__libc_freeres_ptrs" __sec_comment)))
 268 #  define __libc_freeres_fn_section \
 269   __attribute__ ((section ("__libc_freeres_fn")))
 270 # else /* Not ELF: a.out */
 271 #  ifdef HAVE_XCOFF
 272 /* XCOFF does not support .stabs.
 273    The native aix linker will remove the .stab and .stabstr sections
 274    The gnu linker will have a fatal error if there is a relocation for
 275    symbol in the .stab section.  Silently disable this macro.  */
 276 #   define link_warning(symbol, msg)
 277 #  else
 278 #   define link_warning(symbol, msg)            \
 279      asm (".stabs \"" msg "\",30,0,0,0\n\t"     \
 280           ".stabs \"" __SYMBOL_PREFIX #symbol "\",1,0,0,0\n");
 281 #  endif /* XCOFF */
 282 #  define libc_freeres_ptr(decl) decl
 283 #  define __libc_freeres_fn_section
 284 # endif
 285 #else
 286 /* We will never be heard; they will all die horribly.  */
 287 # define link_warning(symbol, msg)
 288 # define libc_freeres_ptr(decl) decl
 289 # define __libc_freeres_fn_section
 290 #endif
 291 #define libc_freeres_fn(name)   \
 292   static void name (void) __attribute_used__ __libc_freeres_fn_section; \
 293   text_set_element (__libc_subfreeres, name);                           \
 294   static void name (void)
 295
 296 /* A canned warning for sysdeps/stub functions.  */
 297 #define stub_warning(name) \
 298   link_warning (name, \
 299                 "warning: " #name " is not implemented and will always fail")
 300
 301
 302 /* Declare SYMBOL to be TYPE (`function' or `object') and of SIZE bytes,
 303    when the assembler supports such declarations (such as in ELF).
 304    This is only necessary when defining something in assembly, or playing
 305    funny alias games where the size should be other than what the compiler
 306    thinks it is.  */
 307 #define declare_symbol(symbol, type, size) \
 308   declare_symbol_1 (symbol, type, size)
 309 #ifdef ASM_TYPE_DIRECTIVE_PREFIX
 310 # ifdef __ASSEMBLER__
 311 #  define declare_symbol_1(symbol, type, size) \
 312     .type C_SYMBOL_NAME (symbol), \
 313           declare_symbol_1_paste (ASM_TYPE_DIRECTIVE_PREFIX, type), size
 314 #  define declare_symbol_1_paste(a, b)  declare_symbol_1_paste_1 (a,b)
 315 #  define declare_symbol_1_paste_1(a,b) a##b
 316 # else /* Not __ASSEMBLER__.  */
 317 #  define declare_symbol_1(symbol, type, size) \
 318     asm (".type " __SYMBOL_PREFIX #symbol ", " \
 319          declare_symbol_1_stringify (ASM_TYPE_DIRECTIVE_PREFIX) #type \
 320          "\n\t.size " __SYMBOL_PREFIX #symbol ", " #size);
 321 #  define declare_symbol_1_stringify(x) declare_symbol_1_stringify_1 (x)
 322 #  define declare_symbol_1_stringify_1(x) #x
 323 # endif /* __ASSEMBLER__ */
 324 #else
 325 # define declare_symbol_1(symbol, type, size) /* Nothing.  */
 326 #endif
 327
 328
 329 /*
 330 \f
 331 */
 332
 333 #ifdef HAVE_GNU_LD
 334
 335 /* Symbol set support macros.  */
 336
 337 # ifdef HAVE_ELF
 338
 339 /* Make SYMBOL, which is in the text segment, an element of SET.  */
 340 #  define text_set_element(set, symbol) _elf_set_element(set, symbol)
 341 /* Make SYMBOL, which is in the data segment, an element of SET.  */
 342 #  define data_set_element(set, symbol) _elf_set_element(set, symbol)
 343 /* Make SYMBOL, which is in the bss segment, an element of SET.  */
 344 #  define bss_set_element(set, symbol)  _elf_set_element(set, symbol)
 345
 346 /* These are all done the same way in ELF.
 347    There is a new section created for each set.  */
 348 #  ifdef SHARED
 349 /* When building a shared library, make the set section writable,
 350    because it will need to be relocated at run time anyway.  */
 351 #   define _elf_set_element(set, symbol) \
 352   static const void *__elf_set_##set##_element_##symbol##__ \
 353     __attribute__ ((unused, section (#set))) = &(symbol)
 354 #  else
 355 #   define _elf_set_element(set, symbol) \
 356   static const void *const __elf_set_##set##_element_##symbol##__ \
 357     __attribute__ ((unused, section (#set))) = &(symbol)
 358 #  endif
 359
 360 /* Define SET as a symbol set.  This may be required (it is in a.out) to
 361    be able to use the set's contents.  */
 362 #  define symbol_set_define(set)        symbol_set_declare(set)
 363
 364 /* Declare SET for use in this module, if defined in another module.  */
 365 #  define symbol_set_declare(set) \
 366   extern void *const __start_##set __attribute__ ((__weak__));          \
 367   extern void *const __stop_##set __attribute__ ((__weak__));           \
 368   weak_extern (__start_##set) weak_extern (__stop_##set)
 369
 370 /* Return a pointer (void *const *) to the first element of SET.  */
 371 #  define symbol_set_first_element(set) (&__start_##set)
 372
 373 /* Return true iff PTR (a void *const *) has been incremented
 374    past the last element in SET.  */
 375 #  define symbol_set_end_p(set, ptr)    ((ptr) >= &__stop_##set)
 376
 377 # else  /* Not ELF: a.out.  */
 378
 379 #  ifdef HAVE_XCOFF
 380 /* XCOFF does not support .stabs.
 381    The native aix linker will remove the .stab and .stabstr sections
 382    The gnu linker will have a fatal error if there is a relocation for
 383    symbol in the .stab section.  Silently disable these macros.  */
 384 #   define text_set_element(set, symbol)
 385 #   define data_set_element(set, symbol)
 386 #   define bss_set_element(set, symbol)
 387 #  else
 388 #   define text_set_element(set, symbol)        \
 389     asm (".stabs \"" __SYMBOL_PREFIX #set "\",23,0,0," __SYMBOL_PREFIX #symbol)
 390 #   define data_set_element(set, symbol)        \
 391     asm (".stabs \"" __SYMBOL_PREFIX #set "\",25,0,0," __SYMBOL_PREFIX #symbol)
 392 #   define bss_set_element(set, symbol) ?error Must use initialized data.
 393 #  endif /* XCOFF */
 394 #  define symbol_set_define(set)        void *const (set)[1];
 395 #  define symbol_set_declare(set)       extern void *const (set)[1];
 396
 397 #  define symbol_set_first_element(set) &(set)[1]
 398 #  define symbol_set_end_p(set, ptr)    (*(ptr) == 0)
 399
 400 # endif /* ELF.  */
 401 #else
 402 /* We cannot do anything in generial.  */
 403 # define text_set_element(set, symbol) asm ("")
 404 # define data_set_element(set, symbol) asm ("")
 405 # define bss_set_element(set, symbol) asm ("")
 406 # define symbol_set_define(set)         void *const (set)[1];
 407 # define symbol_set_declare(set)        extern void *const (set)[1];
 408
 409 # define symbol_set_first_element(set)  &(set)[1]
 410 # define symbol_set_end_p(set, ptr)     (*(ptr) == 0)
 411 #endif  /* Have GNU ld.  */
 412
 413 #if DO_VERSIONING
 414 # define symbol_version(real, name, version) \
 415      _symbol_version(real, name, version)
 416 # define default_symbol_version(real, name, version) \
 417      _default_symbol_version(real, name, version)
 418 # ifdef __ASSEMBLER__
 419 #  ifdef HAVE_ASM_GLOBAL_DOT_NAME
 420 #   define _symbol_version(real, name, version) \
 421      .symver real, name##@##version ASM_LINE_SEP                        \
 422      .symver .##real, .##name##@##version
 423 #   define _default_symbol_version(real, name, version) \
 424      .symver real, name##@##@##version ASM_LINE_SEP                     \
 425      .symver .##real, .##name##@##@##version
 426 #  else
 427 #   define _symbol_version(real, name, version) \
 428      .symver real, name##@##version
 429 #   define _default_symbol_version(real, name, version) \
 430      .symver real, name##@##@##version
 431 #  endif
 432 # else
 433 #  ifdef HAVE_ASM_GLOBAL_DOT_NAME
 434 #   define _symbol_version(real, name, version) \
 435      __asm__ (".symver " #real "," #name "@" #version "\n\t"    \
 436               ".symver ." #real ",." #name "@" #version)
 437 #   define _default_symbol_version(real, name, version) \
 438      __asm__ (".symver " #real "," #name "@@" #version "\n\t"   \
 439               ".symver ." #real ",." #name "@@" #version)
 440 #  else
 441 #   define _symbol_version(real, name, version) \
 442      __asm__ (".symver " #real "," #name "@" #version)
 443 #   define _default_symbol_version(real, name, version) \
 444      __asm__ (".symver " #real "," #name "@@" #version)
 445 #  endif
 446 # endif
 447 #else
 448 # define symbol_version(real, name, version)
 449 # define default_symbol_version(real, name, version) \
 450   strong_alias(real, name)
 451 #endif
 452
 453 #if defined HAVE_VISIBILITY_ATTRIBUTE && defined SHARED
 454 # define attribute_hidden __attribute__ ((visibility ("hidden")))
 455 #else
 456 # define attribute_hidden
 457 #endif
 458
 459 #if defined HAVE_TLS_MODEL_ATTRIBUTE
 460 # define attribute_tls_model_ie __attribute__ ((tls_model ("initial-exec")))
 461 #else
 462 # define attribute_tls_model_ie
 463 #endif
 464
 465 /* Handling on non-exported internal names.  We have to do this only
 466    for shared code.  */
 467 #ifdef SHARED
 468 # define INTUSE(name) name##_internal
 469 # define INTDEF(name) strong_alias (name, name##_internal)
 470 # define INTVARDEF(name) \
 471   _INTVARDEF (name, name##_internal)
 472 # if defined HAVE_VISIBILITY_ATTRIBUTE
 473 #  define _INTVARDEF(name, aliasname) \
 474   extern __typeof (name) aliasname __attribute__ ((alias (#name), \
 475                                                    visibility ("hidden")));
 476 # else
 477 #  define _INTVARDEF(name, aliasname) \
 478   extern __typeof (name) aliasname __attribute__ ((alias (#name)));
 479 # endif
 480 # define INTDEF2(name, newname) strong_alias (name, newname##_internal)
 481 # define INTVARDEF2(name, newname) _INTVARDEF (name, newname##_internal)
 482 #else
 483 # define INTUSE(name) name
 484 # define INTDEF(name)
 485 # define INTVARDEF(name)
 486 # define INTDEF2(name, newname)
 487 # define INTVARDEF2(name, newname)
 488 #endif
 489
 490 /* The following macros are used for PLT bypassing within libc.so
 491    (and if needed other libraries similarly).
 492    First of all, you need to have the function prototyped somewhere,
 493    say in foo/foo.h:
 494
 495    int foo (int __bar);
 496
 497    If calls to foo within libc.so should always go to foo defined in libc.so,
 498    then in include/foo.h you add:
 499
 500    libc_hidden_proto (foo)
 501
 502    line and after the foo function definition:
 503
 504    int foo (int __bar)
 505    {
 506      return __bar;
 507    }
 508    libc_hidden_def (foo)
 509
 510    or
 511
 512    int foo (int __bar)
 513    {
 514      return __bar;
 515    }
 516    libc_hidden_weak (foo)
 517
 518    Simularly for global data. If references to foo within libc.so should
 519    always go to foo defined in libc.so, then in include/foo.h you add:
 520
 521    libc_hidden_proto (foo)
 522
 523    line and after foo's definition:
 524
 525    int foo = INITIAL_FOO_VALUE;
 526    libc_hidden_data_def (foo)
 527
 528    or
 529
 530    int foo = INITIAL_FOO_VALUE;
 531    libc_hidden_data_weak (foo)
 532
 533    If foo is normally just an alias (strong or weak) of some other function,
 534    you should use the normal strong_alias first, then add libc_hidden_def
 535    or libc_hidden_weak:
 536
 537    int baz (int __bar)
 538    {
 539      return __bar;
 540    }
 541    strong_alias (baz, foo)
 542    libc_hidden_weak (foo)
 543
 544    If the function should be internal to multiple objects, say ld.so and
 545    libc.so, the best way is to use:
 546
 547    #if !defined NOT_IN_libc || defined IS_IN_rtld
 548    hidden_proto (foo)
 549    #endif
 550
 551    in include/foo.h and the normal macros at all function definitions
 552    depending on what DSO they belong to.
 553
 554    If versioned_symbol macro is used to define foo,
 555    libc_hidden_ver macro should be used, as in:
 556
 557    int __real_foo (int __bar)
 558    {
 559      return __bar;
 560    }
 561    versioned_symbol (libc, __real_foo, foo, GLIBC_2_1);
 562    libc_hidden_ver (__real_foo, foo)  */
 563
 564 #if defined SHARED && defined DO_VERSIONING \
 565     && !defined HAVE_BROKEN_ALIAS_ATTRIBUTE && !defined NO_HIDDEN
 566 # ifndef __ASSEMBLER__
 567 #  if !defined HAVE_VISIBILITY_ATTRIBUTE \
 568       || defined HAVE_BROKEN_VISIBILITY_ATTRIBUTE
 569 #   define __hidden_proto_hiddenattr(attrs...)
 570 #  else
 571 #   define __hidden_proto_hiddenattr(attrs...) \
 572   __attribute__ ((visibility ("hidden"), ##attrs))
 573 #  endif
 574 #  define hidden_proto(name, attrs...) \
 575   __hidden_proto (name, __GI_##name, ##attrs)
 576 #  define __hidden_proto(name, internal, attrs...) \
 577   extern __typeof (name) internal; \
 578   extern __typeof (name) name __asm__ (__hidden_asmname (#internal)) \
 579   __hidden_proto_hiddenattr (attrs);
 580 #  define __hidden_asmname(name) \
 581   __hidden_asmname1 (__USER_LABEL_PREFIX__, name)
 582 #  define __hidden_asmname1(prefix, name) __hidden_asmname2(prefix, name)
 583 #  define __hidden_asmname2(prefix, name) #prefix name
 584 #  ifdef HAVE_ASM_SET_DIRECTIVE
 585 #   define __hidden_def1(original, alias)                       \
 586   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP       \
 587   .set C_SYMBOL_NAME (alias), C_SYMBOL_NAME (original)
 588 #   ifdef HAVE_ASM_GLOBAL_DOT_NAME
 589 #     define __hidden_dot_def1(original, alias)  ASM_LINE_SEP   \
 590   ASM_GLOBAL_DIRECTIVE C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP   \
 591   .set C_SYMBOL_DOT_NAME (alias), C_SYMBOL_DOT_NAME (original)
 592 #   else
 593 #     define __hidden_dot_def1(original, alias)
 594 #   endif
 595 #  else
 596 #   define __hidden_def1(original, alias)                       \
 597   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP       \
 598   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 599 #   ifdef HAVE_ASM_GLOBAL_DOT_NAME
 600 #    define __hidden_dot_def1(original, alias)  ASM_LINE_SEP    \
 601   ASM_GLOBAL_DIRECTIVE C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP   \
 602   C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original)
 603 #   else
 604 #    define __hidden_dot_def1(original, alias)
 605 #   endif
 606 #  endif
 607 #  define __hidden_def2(...) #__VA_ARGS__
 608 #  define __hidden_def3(...) __hidden_def2 (__VA_ARGS__)
 609 #  define hidden_def(name)                                      \
 610   __asm__ (__hidden_def3 (__hidden_def1 (__GI_##name, name) \
 611   __hidden_dot_def1 (__GI_##name, name)));
 612 #  define hidden_data_def(name)                                 \
 613   __asm__ (__hidden_def3 (__hidden_def1 (__GI_##name, name)));
 614 #  define hidden_ver(local, name)                               \
 615   __asm__ (__hidden_def3 (__hidden_def1 (local, __GI_##name) \
 616   __hidden_dot_def1 (local, __GI_##name)));
 617 #  define hidden_data_ver(local, name)                          \
 618   __asm__ (__hidden_def3 (__hidden_def1 (local, __GI_##name)));
 619 #  ifdef HAVE_WEAK_SYMBOLS
 620 #   ifdef HAVE_ASM_WEAKEXT_DIRECTIVE
 621 #    define __hidden_weak1(original, alias)                     \
 622   .weakext C_SYMBOL_NAME (alias), C_SYMBOL_NAME (original)
 623 #    ifdef HAVE_ASM_GLOBAL_DOT_NAME
 624 #     define __hidden_dot_weak1(original, alias)        ASM_LINE_SEP    \
 625   .weakext C_SYMBOL_DOT_NAME (alias), C_SYMBOL_DOT_NAME (original)
 626 #    else
 627 #     define __hidden_dot_weak1(original, alias)
 628 #    endif
 629 #   else /* ! HAVE_ASM_WEAKEXT_DIRECTIVE */
 630 #    define __hidden_weak1(original, alias)                     \
 631   .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP                      \
 632   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 633 #    ifdef HAVE_ASM_GLOBAL_DOT_NAME
 634 #     define __hidden_dot_weak1(original, alias)        ASM_LINE_SEP    \
 635   .weak C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP  \
 636   C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original)
 637 #    else
 638 #     define __hidden_dot_weak1(original, alias)
 639 #    endif
 640 #   endif
 641 #   define hidden_weak(name)                                    \
 642   __asm__ (__hidden_def3 (__hidden_weak1 (__GI_##name, name) \
 643   __hidden_dot_weak1 (__GI_##name, name)));
 644 #   define hidden_data_weak(name)                                       \
 645   __asm__ (__hidden_def3 (__hidden_weak1 (__GI_##name, name)));
 646 #  else
 647 #   define hidden_weak(name) hidden_def (name)
 648 #  endif
 649 # else
 650 /* For assembly, we need to do the opposite of what we do in C:
 651    in assembly gcc __REDIRECT stuff is not in place, so functions
 652    are defined by its normal name and we need to create the
 653    __GI_* alias to it, in C __REDIRECT causes the function definition
 654    to use __GI_* name and we need to add alias to the real name.
 655    There is no reason to use hidden_weak over hidden_def in assembly,
 656    but we provide it for consistency with the C usage.
 657    hidden_proto doesn't make sense for assembly but the equivalent
 658    is to call via the HIDDEN_JUMPTARGET macro einstead of JUMPTARGET.  */
 659 #  define hidden_def(name)      strong_alias (name, __GI_##name)
 660 #  define hidden_weak(name)     hidden_def (name)
 661 #  define hidden_ver(local, name) strong_alias (local, __GI_##name)
 662 #  define hidden_data_def(name) strong_data_alias (name, __GI_##name)
 663 #  define hidden_data_weak(name)        hidden_data_def (name)
 664 #  define hidden_data_ver(local, name) strong_data_alias (local, __GI_##name)
 665 #  ifdef HAVE_ASM_GLOBAL_DOT_NAME
 666 #   define HIDDEN_JUMPTARGET(name) .__GI_##name
 667 #  else
 668 #   define HIDDEN_JUMPTARGET(name) __GI_##name
 669 #  endif
 670 # endif
 671 #else
 672 # ifndef __ASSEMBLER__
 673 #  define hidden_proto(name, attrs...)
 674 # else
 675 #  define HIDDEN_JUMPTARGET(name) JUMPTARGET(name)
 676 # endif /* Not  __ASSEMBLER__ */
 677 # define hidden_weak(name)
 678 # define hidden_def(name)
 679 # define hidden_ver(local, name)
 680 # define hidden_data_weak(name)
 681 # define hidden_data_def(name)
 682 # define hidden_data_ver(local, name)
 683 #endif
 684
 685 #if !defined NOT_IN_libc
 686 # define libc_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 687 # define libc_hidden_def(name) hidden_def (name)
 688 # define libc_hidden_weak(name) hidden_weak (name)
 689 # define libc_hidden_ver(local, name) hidden_ver (local, name)
 690 # define libc_hidden_data_def(name) hidden_data_def (name)
 691 # define libc_hidden_data_weak(name) hidden_data_weak (name)
 692 # define libc_hidden_data_ver(local, name) hidden_data_ver (local, name)
 693 #else
 694 # define libc_hidden_proto(name, attrs...)
 695 # define libc_hidden_def(name)
 696 # define libc_hidden_weak(name)
 697 # define libc_hidden_ver(local, name)
 698 # define libc_hidden_data_def(name)
 699 # define libc_hidden_data_weak(name)
 700 # define libc_hidden_data_ver(local, name)
 701 #endif
 702
 703 #if defined NOT_IN_libc && defined IS_IN_rtld
 704 # define rtld_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 705 # define rtld_hidden_def(name) hidden_def (name)
 706 # define rtld_hidden_weak(name) hidden_weak (name)
 707 # define rtld_hidden_ver(local, name) hidden_ver (local, name)
 708 # define rtld_hidden_data_def(name) hidden_data_def (name)
 709 # define rtld_hidden_data_weak(name) hidden_data_weak (name)
 710 # define rtld_hidden_data_ver(local, name) hidden_data_ver (local, name)
 711 #else
 712 # define rtld_hidden_proto(name, attrs...)
 713 # define rtld_hidden_def(name)
 714 # define rtld_hidden_weak(name)
 715 # define rtld_hidden_ver(local, name)
 716 # define rtld_hidden_data_def(name)
 717 # define rtld_hidden_data_weak(name)
 718 # define rtld_hidden_data_ver(local, name)
 719 #endif
 720
 721 #if defined NOT_IN_libc && defined IS_IN_libm
 722 # define libm_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 723 # define libm_hidden_def(name) hidden_def (name)
 724 # define libm_hidden_weak(name) hidden_weak (name)
 725 # define libm_hidden_ver(local, name) hidden_ver (local, name)
 726 # define libm_hidden_data_def(name) hidden_data_def (name)
 727 # define libm_hidden_data_weak(name) hidden_data_weak (name)
 728 # define libm_hidden_data_ver(local, name) hidden_data_ver (local, name)
 729 #else
 730 # define libm_hidden_proto(name, attrs...)
 731 # define libm_hidden_def(name)
 732 # define libm_hidden_weak(name)
 733 # define libm_hidden_ver(local, name)
 734 # define libm_hidden_data_def(name)
 735 # define libm_hidden_data_weak(name)
 736 # define libm_hidden_data_ver(local, name)
 737 #endif
 738
 739 #endif /* libc-symbols.h */