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) 1995-1998,2000-2003,2004,2005,2006
   4         Free Software Foundation, Inc.
   5    This file is part of the GNU C Library.
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU Lesser General Public
   9    License as published by the Free Software Foundation; either
  10    version 2.1 of the License, or (at your option) any later version.
  11
  12    The GNU C Library is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15    Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public
  18    License along with the GNU C Library; if not, write to the Free
  19    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  20    02111-1307 USA.  */
  21
  22 #ifndef _LIBC_SYMBOLS_H
  23 #define _LIBC_SYMBOLS_H 1
  24
  25 /* This file's macros are included implicitly in the compilation of every
  26    file in the C library by -imacros.
  27
  28    We include config.h which is generated by configure.
  29    It should define for us the following symbols:
  30
  31    * HAVE_ASM_SET_DIRECTIVE if we have `.set B, A' instead of `A = B'.
  32    * ASM_GLOBAL_DIRECTIVE with `.globl' or `.global'.
  33    * ASM_TYPE_DIRECTIVE_PREFIX with `@' or `#' or whatever for .type,
  34      or leave it undefined if there is no .type directive.
  35    * HAVE_ELF if using ELF, which supports weak symbols using `.weak'.
  36    * HAVE_ASM_WEAK_DIRECTIVE if we have weak symbols using `.weak'.
  37    * HAVE_ASM_WEAKEXT_DIRECTIVE if we have weak symbols using `.weakext'.
  38
  39    */
  40
  41 /* This is defined for the compilation of all C library code.  features.h
  42    tests this to avoid inclusion of stubs.h while compiling the library,
  43    before stubs.h has been generated.  Some library code that is shared
  44    with other packages also tests this symbol to see if it is being
  45    compiled as part of the C library.  We must define this before including
  46    config.h, because it makes some definitions conditional on whether libc
  47    itself is being compiled, or just some generator program.  */
  48 #define _LIBC   1
  49
  50 /* Enable declarations of GNU extensions, since we are compiling them.  */
  51 #define _GNU_SOURCE     1
  52 /* And we also need the data for the reentrant functions.  */
  53 #define _REENTRANT      1
  54
  55 #include <config.h>
  56
  57 /* The symbols in all the user (non-_) macros are C symbols.
  58    NO HAVE_ELF implies a.out.  */
  59
  60 #if defined HAVE_ASM_WEAK_DIRECTIVE || defined HAVE_ASM_WEAKEXT_DIRECTIVE
  61 # define HAVE_WEAK_SYMBOLS
  62 #endif
  63
  64 #ifndef __SYMBOL_PREFIX
  65 # ifdef NO_UNDERSCORES
  66 #  define __SYMBOL_PREFIX
  67 # else
  68 #  define __SYMBOL_PREFIX "_"
  69 # endif
  70 #endif
  71
  72 #ifndef C_SYMBOL_NAME
  73 # ifdef NO_UNDERSCORES
  74 #  define C_SYMBOL_NAME(name) name
  75 # else
  76 #  define C_SYMBOL_NAME(name) _##name
  77 # endif
  78 #endif
  79
  80 #ifndef ASM_LINE_SEP
  81 # define ASM_LINE_SEP ;
  82 #endif
  83
  84 #ifdef HAVE_ASM_GLOBAL_DOT_NAME
  85 # ifndef C_SYMBOL_DOT_NAME
  86 #  if defined __GNUC__ && defined __GNUC_MINOR__ \
  87       && (__GNUC__ << 16) + __GNUC_MINOR__ >= (3 << 16) + 1
  88 #   define C_SYMBOL_DOT_NAME(name) .name
  89 #  else
  90 #   define C_SYMBOL_DOT_NAME(name) .##name
  91 #  endif
  92 # endif
  93 #endif
  94
  95 #ifndef __ASSEMBLER__
  96 /* GCC understands weak symbols and aliases; use its interface where
  97    possible, instead of embedded assembly language.  */
  98
  99 /* Define ALIASNAME as a strong alias for NAME.  */
 100 # define strong_alias(name, aliasname) _strong_alias(name, aliasname)
 101 # define _strong_alias(name, aliasname) \
 102   extern __typeof (name) aliasname __attribute__ ((alias (#name)));
 103
 104 /* This comes between the return type and function name in
 105    a function definition to make that definition weak.  */
 106 # define weak_function __attribute__ ((weak))
 107 # define weak_const_function __attribute__ ((weak, __const__))
 108
 109 # ifdef HAVE_WEAK_SYMBOLS
 110
 111 /* Define ALIASNAME as a weak alias for NAME.
 112    If weak aliases are not available, this defines a strong alias.  */
 113 #  define weak_alias(name, aliasname) _weak_alias (name, aliasname)
 114 #  define _weak_alias(name, aliasname) \
 115   extern __typeof (name) aliasname __attribute__ ((weak, alias (#name)));
 116
 117 /* Declare SYMBOL as weak undefined symbol (resolved to 0 if not defined).  */
 118 #  define weak_extern(symbol) _weak_extern (weak symbol)
 119 #  define _weak_extern(expr) _Pragma (#expr)
 120
 121 # else
 122
 123 #  define weak_alias(name, aliasname) strong_alias(name, aliasname)
 124 #  define weak_extern(symbol) /* Nothing. */
 125
 126 # endif
 127
 128 #else /* __ASSEMBLER__ */
 129
 130 # ifdef HAVE_ASM_SET_DIRECTIVE
 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   .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original) ASM_LINE_SEP      \
 135   ASM_GLOBAL_DIRECTIVE C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP           \
 136   .set C_SYMBOL_DOT_NAME (alias),C_SYMBOL_DOT_NAME (original)
 137 #   define strong_data_alias(original, alias)                           \
 138   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP               \
 139   .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original)
 140 #  else
 141 #   define strong_alias(original, alias)                                \
 142   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP               \
 143   .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original)
 144 #   define strong_data_alias(original, alias) strong_alias(original, alias)
 145 #  endif
 146 # else
 147 #  ifdef HAVE_ASM_GLOBAL_DOT_NAME
 148 #   define strong_alias(original, alias)                                \
 149   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP               \
 150   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) ASM_LINE_SEP         \
 151   ASM_GLOBAL_DIRECTIVE C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP           \
 152   C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original)
 153 #   define strong_data_alias(original, alias)                           \
 154   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP               \
 155   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 156 #  else
 157 #   define strong_alias(original, alias)                                \
 158   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP               \
 159   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 160 #   define strong_data_alias(original, alias) strong_alias(original, alias)
 161 #  endif
 162 # endif
 163
 164 # ifdef HAVE_WEAK_SYMBOLS
 165 #  ifdef HAVE_ASM_WEAKEXT_DIRECTIVE
 166 #   ifdef HAVE_ASM_GLOBAL_DOT_NAME
 167 #    define weak_alias(original, alias)                                 \
 168   .weakext C_SYMBOL_NAME (alias), C_SYMBOL_NAME (original) ASM_LINE_SEP \
 169   .weakext C_SYMBOL_DOT_NAME (alias), C_SYMBOL_DOT_NAME (original)
 170 #   else
 171 #    define weak_alias(original, alias)                                 \
 172   .weakext C_SYMBOL_NAME (alias), C_SYMBOL_NAME (original)
 173 #   endif
 174 #   define weak_extern(symbol)                                          \
 175   .weakext C_SYMBOL_NAME (symbol)
 176
 177 #  else /* ! HAVE_ASM_WEAKEXT_DIRECTIVE */
 178
 179 #   ifdef HAVE_ASM_GLOBAL_DOT_NAME
 180 #    define weak_alias(original, alias)                                 \
 181   .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP                              \
 182   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) ASM_LINE_SEP         \
 183   .weak C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP                          \
 184   C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original)
 185 #   else
 186 #    define weak_alias(original, alias)                                 \
 187   .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP                              \
 188   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 189 #   endif
 190
 191 #   define weak_extern(symbol)                                          \
 192   .weak C_SYMBOL_NAME (symbol)
 193
 194 #  endif /* ! HAVE_ASM_WEAKEXT_DIRECTIVE */
 195
 196 # else /* ! HAVE_WEAK_SYMBOLS */
 197
 198 #  define weak_alias(original, alias) strong_alias(original, alias)
 199 #  define weak_extern(symbol) /* Nothing */
 200 # endif /* ! HAVE_WEAK_SYMBOLS */
 201
 202 #endif /* __ASSEMBLER__ */
 203
 204 /* On some platforms we can make internal function calls (i.e., calls of
 205    functions not exported) a bit faster by using a different calling
 206    convention.  */
 207 #ifndef internal_function
 208 # define internal_function      /* empty */
 209 #endif
 210
 211 /* Prepare for the case that `__builtin_expect' is not available.  */
 212 #ifndef HAVE_BUILTIN_EXPECT
 213 # define __builtin_expect(expr, val) (expr)
 214 #endif
 215
 216 /* Determine the return address.  */
 217 #define RETURN_ADDRESS(nr) \
 218   __builtin_extract_return_addr (__builtin_return_address (nr))
 219
 220 /* When a reference to SYMBOL is encountered, the linker will emit a
 221    warning message MSG.  */
 222 #ifdef HAVE_ELF
 223
 224 /* We want the .gnu.warning.SYMBOL section to be unallocated.  */
 225 # ifdef HAVE_ASM_PREVIOUS_DIRECTIVE
 226 #  define __make_section_unallocated(section_string)    \
 227   asm (".section " section_string "\n\t.previous");
 228 # elif defined HAVE_ASM_POPSECTION_DIRECTIVE
 229 #  define __make_section_unallocated(section_string)    \
 230   asm (".pushsection " section_string "\n\t.popsection");
 231 # else
 232 #  define __make_section_unallocated(section_string)
 233 # endif
 234
 235 /* Tacking on "\n\t#" to the section name makes gcc put it's bogus
 236    section attributes on what looks like a comment to the assembler.  */
 237 # ifdef HAVE_SECTION_QUOTES
 238 #  define __sec_comment "\"\n\t#\""
 239 # else
 240 #  define __sec_comment "\n\t#"
 241 # endif
 242 # define link_warning(symbol, msg) \
 243   __make_section_unallocated (".gnu.warning." #symbol) \
 244   static const char __evoke_link_warning_##symbol[]     \
 245     __attribute__ ((used, section (".gnu.warning." #symbol __sec_comment))) \
 246     = msg;
 247 # define libc_freeres_ptr(decl) \
 248   __make_section_unallocated ("__libc_freeres_ptrs, \"aw\", %nobits") \
 249   decl __attribute__ ((section ("__libc_freeres_ptrs" __sec_comment)))
 250 # define __libc_freeres_fn_section \
 251   __attribute__ ((section ("__libc_freeres_fn")))
 252 #else /* Not ELF: a.out */
 253 # ifdef HAVE_XCOFF
 254 /* XCOFF does not support .stabs.
 255    The native aix linker will remove the .stab and .stabstr sections
 256    The gnu linker will have a fatal error if there is a relocation for
 257    symbol in the .stab section.  Silently disable this macro.  */
 258 #  define link_warning(symbol, msg)
 259 # else
 260 #  define link_warning(symbol, msg)             \
 261      asm (".stabs \"" msg "\",30,0,0,0\n\t"     \
 262           ".stabs \"" __SYMBOL_PREFIX #symbol "\",1,0,0,0\n");
 263 # endif /* XCOFF */
 264 # define libc_freeres_ptr(decl) decl
 265 # define __libc_freeres_fn_section
 266 #endif
 267 #define libc_freeres_fn(name)   \
 268   static void name (void) __attribute_used__ __libc_freeres_fn_section; \
 269   text_set_element (__libc_subfreeres, name);                           \
 270   static void name (void)
 271
 272 /* A canned warning for sysdeps/stub functions.  */
 273 #define stub_warning(name) \
 274   __make_section_unallocated (".gnu.glibc-stub." #name) \
 275   link_warning (name, \
 276                 "warning: " #name " is not implemented and will always fail")
 277
 278 /* Warning for linking functions calling dlopen into static binaries.  */
 279 #ifdef SHARED
 280 #define static_link_warning(name)
 281 #else
 282 #define static_link_warning(name) static_link_warning1(name)
 283 #define static_link_warning1(name) \
 284   link_warning(name, "Using '" #name "' in statically linked applications \
 285 requires at runtime the shared libraries from the glibc version used \
 286 for linking")
 287 #endif
 288
 289 /* Declare SYMBOL to be TYPE (`function' or `object') and of SIZE bytes,
 290    when the assembler supports such declarations (such as in ELF).
 291    This is only necessary when defining something in assembly, or playing
 292    funny alias games where the size should be other than what the compiler
 293    thinks it is.  */
 294 #define declare_symbol(symbol, type, size) \
 295   declare_symbol_1 (symbol, type, size)
 296 #ifdef ASM_TYPE_DIRECTIVE_PREFIX
 297 # ifdef __ASSEMBLER__
 298 #  define declare_symbol_1(symbol, type, size) \
 299     .type C_SYMBOL_NAME (symbol), \
 300           declare_symbol_1_paste (ASM_TYPE_DIRECTIVE_PREFIX, type), size
 301 #  define declare_symbol_1_paste(a, b)  declare_symbol_1_paste_1 (a,b)
 302 #  define declare_symbol_1_paste_1(a,b) a##b
 303 # else /* Not __ASSEMBLER__.  */
 304 #  define declare_symbol_1(symbol, type, size) \
 305     asm (".type " __SYMBOL_PREFIX #symbol ", " \
 306          declare_symbol_1_stringify (ASM_TYPE_DIRECTIVE_PREFIX) #type \
 307          "\n\t.size " __SYMBOL_PREFIX #symbol ", " #size);
 308 #  define declare_symbol_1_stringify(x) declare_symbol_1_stringify_1 (x)
 309 #  define declare_symbol_1_stringify_1(x) #x
 310 # endif /* __ASSEMBLER__ */
 311 #else
 312 # define declare_symbol_1(symbol, type, size) /* Nothing.  */
 313 #endif
 314
 315
 316 /*
 317 \f
 318 */
 319
 320 /* Symbol set support macros.  */
 321
 322 #ifdef HAVE_ELF
 323
 324 /* Make SYMBOL, which is in the text segment, an element of SET.  */
 325 # define text_set_element(set, symbol)  _elf_set_element(set, symbol)
 326 /* Make SYMBOL, which is in the data segment, an element of SET.  */
 327 # define data_set_element(set, symbol)  _elf_set_element(set, symbol)
 328 /* Make SYMBOL, which is in the bss segment, an element of SET.  */
 329 # define bss_set_element(set, symbol)   _elf_set_element(set, symbol)
 330
 331 /* These are all done the same way in ELF.
 332    There is a new section created for each set.  */
 333 # ifdef SHARED
 334 /* When building a shared library, make the set section writable,
 335    because it will need to be relocated at run time anyway.  */
 336 #  define _elf_set_element(set, symbol) \
 337   static const void *__elf_set_##set##_element_##symbol##__ \
 338     __attribute__ ((used, section (#set))) = &(symbol)
 339 # else
 340 #  define _elf_set_element(set, symbol) \
 341   static const void *const __elf_set_##set##_element_##symbol##__ \
 342     __attribute__ ((used, section (#set))) = &(symbol)
 343 # endif
 344
 345 /* Define SET as a symbol set.  This may be required (it is in a.out) to
 346    be able to use the set's contents.  */
 347 # define symbol_set_define(set) symbol_set_declare(set)
 348
 349 /* Declare SET for use in this module, if defined in another module.
 350    In a shared library, this is always local to that shared object.
 351    For static linking, the set might be wholly absent and so we use
 352    weak references.  */
 353 # define symbol_set_declare(set) \
 354   extern char const __start_##set[] __symbol_set_attribute; \
 355   extern char const __stop_##set[] __symbol_set_attribute;
 356 # ifdef SHARED
 357 #  define __symbol_set_attribute attribute_hidden
 358 # else
 359 #  define __symbol_set_attribute __attribute__ ((weak))
 360 # endif
 361
 362 /* Return a pointer (void *const *) to the first element of SET.  */
 363 # define symbol_set_first_element(set)  ((void *const *) (&__start_##set))
 364
 365 /* Return true iff PTR (a void *const *) has been incremented
 366    past the last element in SET.  */
 367 # define symbol_set_end_p(set, ptr) ((ptr) >= (void *const *) &__stop_##set)
 368
 369 #else   /* Not ELF: a.out.  */
 370
 371 # ifdef HAVE_XCOFF
 372 /* XCOFF does not support .stabs.
 373    The native aix linker will remove the .stab and .stabstr sections
 374    The gnu linker will have a fatal error if there is a relocation for
 375    symbol in the .stab section.  Silently disable these macros.  */
 376 #  define text_set_element(set, symbol)
 377 #  define data_set_element(set, symbol)
 378 #  define bss_set_element(set, symbol)
 379 # else
 380 #  define text_set_element(set, symbol) \
 381     asm (".stabs \"" __SYMBOL_PREFIX #set "\",23,0,0," __SYMBOL_PREFIX #symbol)
 382 #  define data_set_element(set, symbol) \
 383     asm (".stabs \"" __SYMBOL_PREFIX #set "\",25,0,0," __SYMBOL_PREFIX #symbol)
 384 #  define bss_set_element(set, symbol)  ?error Must use initialized data.
 385 # endif /* XCOFF */
 386 # define symbol_set_define(set) void *const (set)[1];
 387 # define symbol_set_declare(set)        extern void *const (set)[1];
 388
 389 # define symbol_set_first_element(set)  &(set)[1]
 390 # define symbol_set_end_p(set, ptr)     (*(ptr) == 0)
 391
 392 #endif  /* ELF.  */
 393
 394 #if DO_VERSIONING
 395 # define symbol_version(real, name, version) \
 396      _symbol_version(real, name, version)
 397 # define default_symbol_version(real, name, version) \
 398      _default_symbol_version(real, name, version)
 399 # ifdef __ASSEMBLER__
 400 #  ifdef HAVE_ASM_GLOBAL_DOT_NAME
 401 #   define _symbol_version(real, name, version) \
 402      .symver real, name##@##version ASM_LINE_SEP                        \
 403      .symver C_SYMBOL_DOT_NAME(real), C_SYMBOL_DOT_NAME(name##@##version)
 404 #   define _default_symbol_version(real, name, version) \
 405      .symver real, name##@##@##version ASM_LINE_SEP                     \
 406      .symver C_SYMBOL_DOT_NAME(real), C_SYMBOL_DOT_NAME(name##@##@##version)
 407 #  else
 408 #   define _symbol_version(real, name, version) \
 409      .symver real, name##@##version
 410 #   define _default_symbol_version(real, name, version) \
 411      .symver real, name##@##@##version
 412 #  endif
 413 # else
 414 #  ifdef HAVE_ASM_GLOBAL_DOT_NAME
 415 #   define _symbol_version(real, name, version) \
 416      __asm__ (".symver " #real "," #name "@" #version "\n\t"    \
 417               ".symver ." #real ",." #name "@" #version)
 418 #   define _default_symbol_version(real, name, version) \
 419      __asm__ (".symver " #real "," #name "@@" #version "\n\t"   \
 420               ".symver ." #real ",." #name "@@" #version)
 421 #  else
 422 #   define _symbol_version(real, name, version) \
 423      __asm__ (".symver " #real "," #name "@" #version)
 424 #   define _default_symbol_version(real, name, version) \
 425      __asm__ (".symver " #real "," #name "@@" #version)
 426 #  endif
 427 # endif
 428 #else
 429 # define symbol_version(real, name, version)
 430 # define default_symbol_version(real, name, version) \
 431   strong_alias(real, name)
 432 #endif
 433
 434 #if defined HAVE_VISIBILITY_ATTRIBUTE \
 435     && (defined SHARED || defined LIBC_NONSHARED)
 436 # define attribute_hidden __attribute__ ((visibility ("hidden")))
 437 #else
 438 # define attribute_hidden
 439 #endif
 440
 441 #ifdef HAVE_TLS_MODEL_ATTRIBUTE
 442 # define attribute_tls_model_ie __attribute__ ((tls_model ("initial-exec")))
 443 #else
 444 # define attribute_tls_model_ie
 445 #endif
 446
 447 #ifdef HAVE_Z_RELRO
 448 # define attribute_relro __attribute__ ((section (".data.rel.ro")))
 449 #else
 450 # define attribute_relro
 451 #endif
 452
 453 /* Handling on non-exported internal names.  We have to do this only
 454    for shared code.  */
 455 #ifdef SHARED
 456 # define INTUSE(name) name##_internal
 457 # define INTDEF(name) strong_alias (name, name##_internal)
 458 # define INTVARDEF(name) \
 459   _INTVARDEF (name, name##_internal)
 460 # if defined HAVE_VISIBILITY_ATTRIBUTE
 461 #  define _INTVARDEF(name, aliasname) \
 462   extern __typeof (name) aliasname __attribute__ ((alias (#name), \
 463                                                    visibility ("hidden")));
 464 # else
 465 #  define _INTVARDEF(name, aliasname) \
 466   extern __typeof (name) aliasname __attribute__ ((alias (#name)));
 467 # endif
 468 # define INTDEF2(name, newname) strong_alias (name, newname##_internal)
 469 # define INTVARDEF2(name, newname) _INTVARDEF (name, newname##_internal)
 470 #else
 471 # define INTUSE(name) name
 472 # define INTDEF(name)
 473 # define INTVARDEF(name)
 474 # define INTDEF2(name, newname)
 475 # define INTVARDEF2(name, newname)
 476 #endif
 477
 478 /* The following macros are used for PLT bypassing within libc.so
 479    (and if needed other libraries similarly).
 480    First of all, you need to have the function prototyped somewhere,
 481    say in foo/foo.h:
 482
 483    int foo (int __bar);
 484
 485    If calls to foo within libc.so should always go to foo defined in libc.so,
 486    then in include/foo.h you add:
 487
 488    libc_hidden_proto (foo)
 489
 490    line and after the foo function definition:
 491
 492    int foo (int __bar)
 493    {
 494      return __bar;
 495    }
 496    libc_hidden_def (foo)
 497
 498    or
 499
 500    int foo (int __bar)
 501    {
 502      return __bar;
 503    }
 504    libc_hidden_weak (foo)
 505
 506    Similarly for global data.  If references to foo within libc.so should
 507    always go to foo defined in libc.so, then in include/foo.h you add:
 508
 509    libc_hidden_proto (foo)
 510
 511    line and after foo's definition:
 512
 513    int foo = INITIAL_FOO_VALUE;
 514    libc_hidden_data_def (foo)
 515
 516    or
 517
 518    int foo = INITIAL_FOO_VALUE;
 519    libc_hidden_data_weak (foo)
 520
 521    If foo is normally just an alias (strong or weak) to some other function,
 522    you should use the normal strong_alias first, then add libc_hidden_def
 523    or libc_hidden_weak:
 524
 525    int baz (int __bar)
 526    {
 527      return __bar;
 528    }
 529    strong_alias (baz, foo)
 530    libc_hidden_weak (foo)
 531
 532    If the function should be internal to multiple objects, say ld.so and
 533    libc.so, the best way is to use:
 534
 535    #if !defined NOT_IN_libc || defined IS_IN_rtld
 536    hidden_proto (foo)
 537    #endif
 538
 539    in include/foo.h and the normal macros at all function definitions
 540    depending on what DSO they belong to.
 541
 542    If versioned_symbol macro is used to define foo,
 543    libc_hidden_ver macro should be used, as in:
 544
 545    int __real_foo (int __bar)
 546    {
 547      return __bar;
 548    }
 549    versioned_symbol (libc, __real_foo, foo, GLIBC_2_1);
 550    libc_hidden_ver (__real_foo, foo)  */
 551
 552 #if defined SHARED && defined DO_VERSIONING \
 553     && !defined HAVE_BROKEN_ALIAS_ATTRIBUTE && !defined NO_HIDDEN
 554 # ifndef __ASSEMBLER__
 555 #  if !defined HAVE_VISIBILITY_ATTRIBUTE \
 556       || defined HAVE_BROKEN_VISIBILITY_ATTRIBUTE
 557 #   define __hidden_proto_hiddenattr(attrs...)
 558 #  else
 559 #   define __hidden_proto_hiddenattr(attrs...) \
 560   __attribute__ ((visibility ("hidden"), ##attrs))
 561 #  endif
 562 #  define hidden_proto(name, attrs...) \
 563   __hidden_proto (name, __GI_##name, ##attrs)
 564 #  define __hidden_proto(name, internal, attrs...) \
 565   extern __typeof (name) name __asm__ (__hidden_asmname (#internal)) \
 566   __hidden_proto_hiddenattr (attrs);
 567 #  define __hidden_asmname(name) \
 568   __hidden_asmname1 (__USER_LABEL_PREFIX__, name)
 569 #  define __hidden_asmname1(prefix, name) __hidden_asmname2(prefix, name)
 570 #  define __hidden_asmname2(prefix, name) #prefix name
 571 #  define __hidden_ver1(local, internal, name) \
 572   extern __typeof (name) __EI_##name __asm__(__hidden_asmname (#internal)); \
 573   extern __typeof (name) __EI_##name \
 574         __attribute__((alias (__hidden_asmname (#local))))
 575 #  define hidden_ver(local, name)       __hidden_ver1(local, __GI_##name, name);
 576 #  define hidden_data_ver(local, name)  hidden_ver(local, name)
 577 #  define hidden_def(name)              __hidden_ver1(__GI_##name, name, name);
 578 #  define hidden_data_def(name)         hidden_def(name)
 579 #  define hidden_weak(name) \
 580         __hidden_ver1(__GI_##name, name, name) __attribute__((weak));
 581 #  define hidden_data_weak(name)        hidden_weak(name)
 582 # else
 583 /* For assembly, we need to do the opposite of what we do in C:
 584    in assembly gcc __REDIRECT stuff is not in place, so functions
 585    are defined by its normal name and we need to create the
 586    __GI_* alias to it, in C __REDIRECT causes the function definition
 587    to use __GI_* name and we need to add alias to the real name.
 588    There is no reason to use hidden_weak over hidden_def in assembly,
 589    but we provide it for consistency with the C usage.
 590    hidden_proto doesn't make sense for assembly but the equivalent
 591    is to call via the HIDDEN_JUMPTARGET macro instead of JUMPTARGET.  */
 592 #  define hidden_def(name)      strong_alias (name, __GI_##name)
 593 #  define hidden_weak(name)     hidden_def (name)
 594 #  define hidden_ver(local, name) strong_alias (local, __GI_##name)
 595 #  define hidden_data_def(name) strong_data_alias (name, __GI_##name)
 596 #  define hidden_data_weak(name)        hidden_data_def (name)
 597 #  define hidden_data_ver(local, name) strong_data_alias (local, __GI_##name)
 598 #  ifdef HAVE_ASM_GLOBAL_DOT_NAME
 599 #   define HIDDEN_JUMPTARGET(name) .__GI_##name
 600 #  else
 601 #   define HIDDEN_JUMPTARGET(name) __GI_##name
 602 #  endif
 603 # endif
 604 #else
 605 # ifndef __ASSEMBLER__
 606 #  define hidden_proto(name, attrs...)
 607 # else
 608 #  define HIDDEN_JUMPTARGET(name) JUMPTARGET(name)
 609 # endif /* Not  __ASSEMBLER__ */
 610 # define hidden_weak(name)
 611 # define hidden_def(name)
 612 # define hidden_ver(local, name)
 613 # define hidden_data_weak(name)
 614 # define hidden_data_def(name)
 615 # define hidden_data_ver(local, name)
 616 #endif
 617
 618 #if !defined NOT_IN_libc
 619 # define libc_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 620 # define libc_hidden_def(name) hidden_def (name)
 621 # define libc_hidden_weak(name) hidden_weak (name)
 622 # define libc_hidden_ver(local, name) hidden_ver (local, name)
 623 # define libc_hidden_data_def(name) hidden_data_def (name)
 624 # define libc_hidden_data_weak(name) hidden_data_weak (name)
 625 # define libc_hidden_data_ver(local, name) hidden_data_ver (local, name)
 626 #else
 627 # define libc_hidden_proto(name, attrs...)
 628 # define libc_hidden_def(name)
 629 # define libc_hidden_weak(name)
 630 # define libc_hidden_ver(local, name)
 631 # define libc_hidden_data_def(name)
 632 # define libc_hidden_data_weak(name)
 633 # define libc_hidden_data_ver(local, name)
 634 #endif
 635
 636 #if defined NOT_IN_libc && defined IS_IN_rtld
 637 # define rtld_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 638 # define rtld_hidden_def(name) hidden_def (name)
 639 # define rtld_hidden_weak(name) hidden_weak (name)
 640 # define rtld_hidden_ver(local, name) hidden_ver (local, name)
 641 # define rtld_hidden_data_def(name) hidden_data_def (name)
 642 # define rtld_hidden_data_weak(name) hidden_data_weak (name)
 643 # define rtld_hidden_data_ver(local, name) hidden_data_ver (local, name)
 644 #else
 645 # define rtld_hidden_proto(name, attrs...)
 646 # define rtld_hidden_def(name)
 647 # define rtld_hidden_weak(name)
 648 # define rtld_hidden_ver(local, name)
 649 # define rtld_hidden_data_def(name)
 650 # define rtld_hidden_data_weak(name)
 651 # define rtld_hidden_data_ver(local, name)
 652 #endif
 653
 654 #if defined NOT_IN_libc && defined IS_IN_libm
 655 # define libm_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 656 # define libm_hidden_def(name) hidden_def (name)
 657 # define libm_hidden_weak(name) hidden_weak (name)
 658 # define libm_hidden_ver(local, name) hidden_ver (local, name)
 659 # define libm_hidden_data_def(name) hidden_data_def (name)
 660 # define libm_hidden_data_weak(name) hidden_data_weak (name)
 661 # define libm_hidden_data_ver(local, name) hidden_data_ver (local, name)
 662 #else
 663 # define libm_hidden_proto(name, attrs...)
 664 # define libm_hidden_def(name)
 665 # define libm_hidden_weak(name)
 666 # define libm_hidden_ver(local, name)
 667 # define libm_hidden_data_def(name)
 668 # define libm_hidden_data_weak(name)
 669 # define libm_hidden_data_ver(local, name)
 670 #endif
 671
 672 #if defined NOT_IN_libc && defined IS_IN_libresolv
 673 # define libresolv_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 674 # define libresolv_hidden_def(name) hidden_def (name)
 675 # define libresolv_hidden_weak(name) hidden_weak (name)
 676 # define libresolv_hidden_ver(local, name) hidden_ver (local, name)
 677 # define libresolv_hidden_data_def(name) hidden_data_def (name)
 678 # define libresolv_hidden_data_weak(name) hidden_data_weak (name)
 679 # define libresolv_hidden_data_ver(local, name) hidden_data_ver (local, name)
 680 #else
 681 # define libresolv_hidden_proto(name, attrs...)
 682 # define libresolv_hidden_def(name)
 683 # define libresolv_hidden_weak(name)
 684 # define libresolv_hidden_ver(local, name)
 685 # define libresolv_hidden_data_def(name)
 686 # define libresolv_hidden_data_weak(name)
 687 # define libresolv_hidden_data_ver(local, name)
 688 #endif
 689
 690 #if defined NOT_IN_libc && defined IS_IN_librt
 691 # define librt_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 692 # define librt_hidden_def(name) hidden_def (name)
 693 # define librt_hidden_weak(name) hidden_weak (name)
 694 # define librt_hidden_ver(local, name) hidden_ver (local, name)
 695 # define librt_hidden_data_def(name) hidden_data_def (name)
 696 # define librt_hidden_data_weak(name) hidden_data_weak (name)
 697 # define librt_hidden_data_ver(local, name) hidden_data_ver (local, name)
 698 #else
 699 # define librt_hidden_proto(name, attrs...)
 700 # define librt_hidden_def(name)
 701 # define librt_hidden_weak(name)
 702 # define librt_hidden_ver(local, name)
 703 # define librt_hidden_data_def(name)
 704 # define librt_hidden_data_weak(name)
 705 # define librt_hidden_data_ver(local, name)
 706 #endif
 707
 708 #if defined NOT_IN_libc && defined IS_IN_libdl
 709 # define libdl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 710 # define libdl_hidden_def(name) hidden_def (name)
 711 # define libdl_hidden_weak(name) hidden_weak (name)
 712 # define libdl_hidden_ver(local, name) hidden_ver (local, name)
 713 # define libdl_hidden_data_def(name) hidden_data_def (name)
 714 # define libdl_hidden_data_weak(name) hidden_data_weak (name)
 715 # define libdl_hidden_data_ver(local, name) hidden_data_ver (local, name)
 716 #else
 717 # define libdl_hidden_proto(name, attrs...)
 718 # define libdl_hidden_def(name)
 719 # define libdl_hidden_weak(name)
 720 # define libdl_hidden_ver(local, name)
 721 # define libdl_hidden_data_def(name)
 722 # define libdl_hidden_data_weak(name)
 723 # define libdl_hidden_data_ver(local, name)
 724 #endif
 725
 726 #if defined NOT_IN_libc && defined IS_IN_libnss_files
 727 # define libnss_files_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 728 # define libnss_files_hidden_def(name) hidden_def (name)
 729 # define libnss_files_hidden_weak(name) hidden_weak (name)
 730 # define libnss_files_hidden_ver(local, name) hidden_ver (local, name)
 731 # define libnss_files_hidden_data_def(name) hidden_data_def (name)
 732 # define libnss_files_hidden_data_weak(name) hidden_data_weak (name)
 733 # define libnss_files_hidden_data_ver(local, name) hidden_data_ver(local, name)
 734 #else
 735 # define libnss_files_hidden_proto(name, attrs...)
 736 # define libnss_files_hidden_def(name)
 737 # define libnss_files_hidden_weak(name)
 738 # define libnss_files_hidden_ver(local, name)
 739 # define libnss_files_hidden_data_def(name)
 740 # define libnss_files_hidden_data_weak(name)
 741 # define libnss_files_hidden_data_ver(local, name)
 742 #endif
 743
 744 #if defined NOT_IN_libc && defined IS_IN_libnsl
 745 # define libnsl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 746 # define libnsl_hidden_def(name) hidden_def (name)
 747 # define libnsl_hidden_weak(name) hidden_weak (name)
 748 # define libnsl_hidden_ver(local, name) hidden_ver (local, name)
 749 # define libnsl_hidden_data_def(name) hidden_data_def (name)
 750 # define libnsl_hidden_data_weak(name) hidden_data_weak (name)
 751 # define libnsl_hidden_data_ver(local, name) hidden_data_ver (local, name)
 752 #else
 753 # define libnsl_hidden_proto(name, attrs...)
 754 # define libnsl_hidden_def(name)
 755 # define libnsl_hidden_weak(name)
 756 # define libnsl_hidden_ver(local, name)
 757 # define libnsl_hidden_data_def(name)
 758 # define libnsl_hidden_data_weak(name)
 759 # define libnsl_hidden_data_ver(local, name)
 760 #endif
 761
 762 #if defined NOT_IN_libc && defined IS_IN_libnss_nisplus
 763 # define libnss_nisplus_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 764 # define libnss_nisplus_hidden_def(name) hidden_def (name)
 765 # define libnss_nisplus_hidden_weak(name) hidden_weak (name)
 766 # define libnss_nisplus_hidden_ver(local, name) hidden_ver (local, name)
 767 # define libnss_nisplus_hidden_data_def(name) hidden_data_def (name)
 768 # define libnss_nisplus_hidden_data_weak(name) hidden_data_weak (name)
 769 # define libnss_nisplus_hidden_data_ver(local, name) hidden_data_ver (local, name)
 770 #else
 771 # define libnss_nisplus_hidden_proto(name, attrs...)
 772 # define libnss_nisplus_hidden_def(name)
 773 # define libnss_nisplus_hidden_weak(name)
 774 # define libnss_nisplus_hidden_ver(local, name)
 775 # define libnss_nisplus_hidden_data_def(name)
 776 # define libnss_nisplus_hidden_data_weak(name)
 777 # define libnss_nisplus_hidden_data_ver(local, name)
 778 #endif
 779
 780 #ifdef HAVE_BUILTIN_REDIRECTION
 781 # define libc_hidden_builtin_proto(name, attrs...) libc_hidden_proto (name, ##attrs)
 782 # define libc_hidden_builtin_def(name) libc_hidden_def (name)
 783 # define libc_hidden_builtin_weak(name) libc_hidden_weak (name)
 784 # define libc_hidden_builtin_ver(local, name) libc_hidden_ver (local, name)
 785 # ifdef __ASSEMBLER__
 786 #  define HIDDEN_BUILTIN_JUMPTARGET(name) HIDDEN_JUMPTARGET(name)
 787 # endif
 788 #else
 789 # define libc_hidden_builtin_proto(name, attrs...)
 790 # define libc_hidden_builtin_def(name)
 791 # define libc_hidden_builtin_weak(name)
 792 # define libc_hidden_builtin_ver(local, name)
 793 # ifdef __ASSEMBLER__
 794 #  define HIDDEN_BUILTIN_JUMPTARGET(name) JUMPTARGET(name)
 795 # endif
 796 #endif
 797
 798 #if defined NOT_IN_libc && defined IS_IN_libutil
 799 # define libutil_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 800 # define libutil_hidden_def(name) hidden_def (name)
 801 # define libutil_hidden_weak(name) hidden_weak (name)
 802 # define libutil_hidden_ver(local, name) hidden_ver (local, name)
 803 # define libutil_hidden_data_def(name) hidden_data_def (name)
 804 # define libutil_hidden_data_weak(name) hidden_data_weak (name)
 805 # define libutil_hidden_data_ver(local, name) hidden_data_ver (local, name)
 806 #else
 807 # define libutil_hidden_proto(name, attrs...)
 808 # define libutil_hidden_def(name)
 809 # define libutil_hidden_weak(name)
 810 # define libutil_hidden_ver(local, name)
 811 # define libutil_hidden_data_def(name)
 812 # define libutil_hidden_data_weak(name)
 813 # define libutil_hidden_data_ver(local, name)
 814 #endif
 815
 816 /* Get some dirty hacks.  */
 817 #include <symbol-hacks.h>
 818
 819 /* Move compatibility symbols out of the way by placing them all in a
 820    special section.  */
 821 #ifndef __ASSEMBLER__
 822 # define attribute_compat_text_section \
 823     __attribute__ ((section (".text.compat")))
 824 # define attribute_compat_data_section \
 825     __attribute__ ((section (".data.compat")))
 826 #else
 827 # define compat_text_section .section ".text.compat", "ax";
 828 # define compat_data_section .section ".data.compat", "aw";
 829 #endif
 830
 831 #endif /* libc-symbols.h */