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) 1995-1998,2000,2001,2002,2003 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 (weak symbol)
 120 #  define _weak_extern(expr) _Pragma (#expr)
 121
 122 # else
 123
 124 #  define weak_alias(name, aliasname) strong_alias(name, aliasname)
 125 #  define weak_extern(symbol) /* Nothing. */
 126
 127 # endif
 128
 129 #else /* __ASSEMBLER__ */
 130
 131 # ifdef HAVE_ASM_SET_DIRECTIVE
 132 #  ifdef HAVE_ASM_GLOBAL_DOT_NAME
 133 #   define strong_alias(original, alias)                                \
 134   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP               \
 135   .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original) ASM_LINE_SEP      \
 136   ASM_GLOBAL_DIRECTIVE C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP           \
 137   .set C_SYMBOL_DOT_NAME (alias),C_SYMBOL_DOT_NAME (original)
 138 #   define strong_data_alias(original, alias)                           \
 139   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP               \
 140   .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original)
 141 #  else
 142 #   define strong_alias(original, alias)                                \
 143   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP               \
 144   .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original)
 145 #   define strong_data_alias(original, alias) strong_alias(original, alias)
 146 #  endif
 147 # else
 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   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) ASM_LINE_SEP         \
 152   ASM_GLOBAL_DIRECTIVE C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP           \
 153   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   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   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 161 #   define strong_data_alias(original, alias) strong_alias(original, alias)
 162 #  endif
 163 # endif
 164
 165 # ifdef HAVE_WEAK_SYMBOLS
 166 #  ifdef HAVE_ASM_WEAKEXT_DIRECTIVE
 167 #   ifdef HAVE_ASM_GLOBAL_DOT_NAME
 168 #    define weak_alias(original, alias)                                 \
 169   .weakext C_SYMBOL_NAME (alias), C_SYMBOL_NAME (original) ASM_LINE_SEP \
 170   .weakext C_SYMBOL_DOT_NAME (alias), C_SYMBOL_DOT_NAME (original)
 171 #   else
 172 #    define weak_alias(original, alias)                                 \
 173   .weakext C_SYMBOL_NAME (alias), C_SYMBOL_NAME (original)
 174 #   endif
 175 #   define weak_extern(symbol)                                          \
 176   .weakext C_SYMBOL_NAME (symbol)
 177
 178 #  else /* ! HAVE_ASM_WEAKEXT_DIRECTIVE */
 179
 180 #   ifdef HAVE_ASM_GLOBAL_DOT_NAME
 181 #    define weak_alias(original, alias)                                 \
 182   .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP                              \
 183   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) ASM_LINE_SEP         \
 184   .weak C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP                          \
 185   C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original)
 186 #   else
 187 #    define weak_alias(original, alias)                                 \
 188   .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP                              \
 189   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 190 #   endif
 191
 192 #   define weak_extern(symbol)                                          \
 193   .weak C_SYMBOL_NAME (symbol)
 194
 195 #  endif /* ! HAVE_ASM_WEAKEXT_DIRECTIVE */
 196
 197 # else /* ! HAVE_WEAK_SYMBOLS */
 198
 199 #  define weak_alias(original, alias) strong_alias(original, alias)
 200 #  define weak_extern(symbol) /* Nothing */
 201 # endif /* ! HAVE_WEAK_SYMBOLS */
 202
 203 #endif /* __ASSEMBLER__ */
 204
 205 /* On some platforms we can make internal function calls (i.e., calls of
 206    functions not exported) a bit faster by using a different calling
 207    convention.  */
 208 #ifndef internal_function
 209 # define internal_function      /* empty */
 210 #endif
 211
 212 /* Prepare for the case that `__builtin_expect' is not available.  */
 213 #ifndef HAVE_BUILTIN_EXPECT
 214 # define __builtin_expect(expr, val) (expr)
 215 #endif
 216
 217 /* Determine the return address.  */
 218 #define RETURN_ADDRESS(nr) \
 219   __builtin_extract_return_addr (__builtin_return_address (nr))
 220
 221 /* When a reference to SYMBOL is encountered, the linker will emit a
 222    warning message MSG.  */
 223 #ifdef HAVE_GNU_LD
 224 # ifdef HAVE_ELF
 225
 226 /* We want the .gnu.warning.SYMBOL section to be unallocated.  */
 227 #  ifdef HAVE_ASM_PREVIOUS_DIRECTIVE
 228 #   define __make_section_unallocated(section_string)   \
 229   asm (".section " section_string "\n\t.previous");
 230 #  elif defined HAVE_ASM_POPSECTION_DIRECTIVE
 231 #   define __make_section_unallocated(section_string)   \
 232   asm (".pushsection " section_string "\n\t.popsection");
 233 #  else
 234 #   define __make_section_unallocated(section_string)
 235 #  endif
 236
 237 /* Tacking on "\n\t#" to the section name makes gcc put it's bogus
 238    section attributes on what looks like a comment to the assembler.  */
 239 #  ifdef HAVE_SECTION_QUOTES
 240 #   define __sec_comment "\"\n\t#\""
 241 #  else
 242 #   define __sec_comment "\n\t#"
 243 #  endif
 244 #  define link_warning(symbol, msg) \
 245   __make_section_unallocated (".gnu.warning." #symbol) \
 246   static const char __evoke_link_warning_##symbol[]     \
 247     __attribute__ ((unused, section (".gnu.warning." #symbol __sec_comment))) \
 248     = msg;
 249 #  define libc_freeres_ptr(decl) \
 250   __make_section_unallocated ("__libc_freeres_ptrs, \"aw\", %nobits") \
 251   decl __attribute__ ((section ("__libc_freeres_ptrs" __sec_comment)))
 252 #  define __libc_freeres_fn_section \
 253   __attribute__ ((section ("__libc_freeres_fn")))
 254 # else /* Not ELF: a.out */
 255 #  ifdef HAVE_XCOFF
 256 /* XCOFF does not support .stabs.
 257    The native aix linker will remove the .stab and .stabstr sections
 258    The gnu linker will have a fatal error if there is a relocation for
 259    symbol in the .stab section.  Silently disable this macro.  */
 260 #   define link_warning(symbol, msg)
 261 #  else
 262 #   define link_warning(symbol, msg)            \
 263      asm (".stabs \"" msg "\",30,0,0,0\n\t"     \
 264           ".stabs \"" __SYMBOL_PREFIX #symbol "\",1,0,0,0\n");
 265 #  endif /* XCOFF */
 266 #  define libc_freeres_ptr(decl) decl
 267 #  define __libc_freeres_fn_section
 268 # endif
 269 #else
 270 /* We will never be heard; they will all die horribly.  */
 271 # define link_warning(symbol, msg)
 272 # define libc_freeres_ptr(decl) decl
 273 # define __libc_freeres_fn_section
 274 #endif
 275 #define libc_freeres_fn(name)   \
 276   static void name (void) __attribute_used__ __libc_freeres_fn_section; \
 277   text_set_element (__libc_subfreeres, name);                           \
 278   static void name (void)
 279
 280 /* A canned warning for sysdeps/stub functions.  */
 281 #define stub_warning(name) \
 282   link_warning (name, \
 283                 "warning: " #name " is not implemented and will always fail")
 284
 285
 286 /* Declare SYMBOL to be TYPE (`function' or `object') and of SIZE bytes,
 287    when the assembler supports such declarations (such as in ELF).
 288    This is only necessary when defining something in assembly, or playing
 289    funny alias games where the size should be other than what the compiler
 290    thinks it is.  */
 291 #define declare_symbol(symbol, type, size) \
 292   declare_symbol_1 (symbol, type, size)
 293 #ifdef ASM_TYPE_DIRECTIVE_PREFIX
 294 # ifdef __ASSEMBLER__
 295 #  define declare_symbol_1(symbol, type, size) \
 296     .type C_SYMBOL_NAME (symbol), \
 297           declare_symbol_1_paste (ASM_TYPE_DIRECTIVE_PREFIX, type), size
 298 #  define declare_symbol_1_paste(a, b)  declare_symbol_1_paste_1 (a,b)
 299 #  define declare_symbol_1_paste_1(a,b) a##b
 300 # else /* Not __ASSEMBLER__.  */
 301 #  define declare_symbol_1(symbol, type, size) \
 302     asm (".type " __SYMBOL_PREFIX #symbol ", " \
 303          declare_symbol_1_stringify (ASM_TYPE_DIRECTIVE_PREFIX) #type \
 304          "\n\t.size " __SYMBOL_PREFIX #symbol ", " #size);
 305 #  define declare_symbol_1_stringify(x) declare_symbol_1_stringify_1 (x)
 306 #  define declare_symbol_1_stringify_1(x) #x
 307 # endif /* __ASSEMBLER__ */
 308 #else
 309 # define declare_symbol_1(symbol, type, size) /* Nothing.  */
 310 #endif
 311
 312
 313 /*
 314 \f
 315 */
 316
 317 #ifdef HAVE_GNU_LD
 318
 319 /* Symbol set support macros.  */
 320
 321 # ifdef HAVE_ELF
 322
 323 /* Make SYMBOL, which is in the text segment, an element of SET.  */
 324 #  define text_set_element(set, symbol) _elf_set_element(set, symbol)
 325 /* Make SYMBOL, which is in the data segment, an element of SET.  */
 326 #  define data_set_element(set, symbol) _elf_set_element(set, symbol)
 327 /* Make SYMBOL, which is in the bss segment, an element of SET.  */
 328 #  define bss_set_element(set, symbol)  _elf_set_element(set, symbol)
 329
 330 /* These are all done the same way in ELF.
 331    There is a new section created for each set.  */
 332 #  ifdef SHARED
 333 /* When building a shared library, make the set section writable,
 334    because it will need to be relocated at run time anyway.  */
 335 #   define _elf_set_element(set, symbol) \
 336   static const void *__elf_set_##set##_element_##symbol##__ \
 337     __attribute__ ((unused, section (#set))) = &(symbol)
 338 #  else
 339 #   define _elf_set_element(set, symbol) \
 340   static const void *const __elf_set_##set##_element_##symbol##__ \
 341     __attribute__ ((unused, section (#set))) = &(symbol)
 342 #  endif
 343
 344 /* Define SET as a symbol set.  This may be required (it is in a.out) to
 345    be able to use the set's contents.  */
 346 #  define symbol_set_define(set)        symbol_set_declare(set)
 347
 348 /* Declare SET for use in this module, if defined in another module.
 349    In a shared library, this is always local to that shared object.
 350    For static linking, the set might be wholly absent and so we use
 351    weak references.  */
 352 #  define symbol_set_declare(set) \
 353   extern char const __start_##set[] __symbol_set_attribute; \
 354   extern char const __stop_##set[] __symbol_set_attribute;
 355 #  ifdef SHARED
 356 #   define __symbol_set_attribute attribute_hidden
 357 #  else
 358 #   define __symbol_set_attribute __attribute__ ((weak))
 359 #  endif
 360
 361 /* Return a pointer (void *const *) to the first element of SET.  */
 362 #  define symbol_set_first_element(set) ((void *const *) (&__start_##set))
 363
 364 /* Return true iff PTR (a void *const *) has been incremented
 365    past the last element in SET.  */
 366 #  define symbol_set_end_p(set, ptr) ((ptr) >= (void *const *) &__stop_##set)
 367
 368 # else  /* Not ELF: a.out.  */
 369
 370 #  ifdef HAVE_XCOFF
 371 /* XCOFF does not support .stabs.
 372    The native aix linker will remove the .stab and .stabstr sections
 373    The gnu linker will have a fatal error if there is a relocation for
 374    symbol in the .stab section.  Silently disable these macros.  */
 375 #   define text_set_element(set, symbol)
 376 #   define data_set_element(set, symbol)
 377 #   define bss_set_element(set, symbol)
 378 #  else
 379 #   define text_set_element(set, symbol)        \
 380     asm (".stabs \"" __SYMBOL_PREFIX #set "\",23,0,0," __SYMBOL_PREFIX #symbol)
 381 #   define data_set_element(set, symbol)        \
 382     asm (".stabs \"" __SYMBOL_PREFIX #set "\",25,0,0," __SYMBOL_PREFIX #symbol)
 383 #   define bss_set_element(set, symbol) ?error Must use initialized data.
 384 #  endif /* XCOFF */
 385 #  define symbol_set_define(set)        void *const (set)[1];
 386 #  define symbol_set_declare(set)       extern void *const (set)[1];
 387
 388 #  define symbol_set_first_element(set) &(set)[1]
 389 #  define symbol_set_end_p(set, ptr)    (*(ptr) == 0)
 390
 391 # endif /* ELF.  */
 392 #else
 393 /* We cannot do anything in generial.  */
 394 # define text_set_element(set, symbol) asm ("")
 395 # define data_set_element(set, symbol) asm ("")
 396 # define bss_set_element(set, symbol) asm ("")
 397 # define symbol_set_define(set)         void *const (set)[1];
 398 # define symbol_set_declare(set)        extern void *const (set)[1];
 399
 400 # define symbol_set_first_element(set)  &(set)[1]
 401 # define symbol_set_end_p(set, ptr)     (*(ptr) == 0)
 402 #endif  /* Have GNU ld.  */
 403
 404 #if DO_VERSIONING
 405 # define symbol_version(real, name, version) \
 406      _symbol_version(real, name, version)
 407 # define default_symbol_version(real, name, version) \
 408      _default_symbol_version(real, name, version)
 409 # ifdef __ASSEMBLER__
 410 #  ifdef HAVE_ASM_GLOBAL_DOT_NAME
 411 #   define _symbol_version(real, name, version) \
 412      .symver real, name##@##version ASM_LINE_SEP                        \
 413      .symver .##real, .##name##@##version
 414 #   define _default_symbol_version(real, name, version) \
 415      .symver real, name##@##@##version ASM_LINE_SEP                     \
 416      .symver .##real, .##name##@##@##version
 417 #  else
 418 #   define _symbol_version(real, name, version) \
 419      .symver real, name##@##version
 420 #   define _default_symbol_version(real, name, version) \
 421      .symver real, name##@##@##version
 422 #  endif
 423 # else
 424 #  ifdef HAVE_ASM_GLOBAL_DOT_NAME
 425 #   define _symbol_version(real, name, version) \
 426      __asm__ (".symver " #real "," #name "@" #version "\n\t"    \
 427               ".symver ." #real ",." #name "@" #version)
 428 #   define _default_symbol_version(real, name, version) \
 429      __asm__ (".symver " #real "," #name "@@" #version "\n\t"   \
 430               ".symver ." #real ",." #name "@@" #version)
 431 #  else
 432 #   define _symbol_version(real, name, version) \
 433      __asm__ (".symver " #real "," #name "@" #version)
 434 #   define _default_symbol_version(real, name, version) \
 435      __asm__ (".symver " #real "," #name "@@" #version)
 436 #  endif
 437 # endif
 438 #else
 439 # define symbol_version(real, name, version)
 440 # define default_symbol_version(real, name, version) \
 441   strong_alias(real, name)
 442 #endif
 443
 444 #if defined HAVE_VISIBILITY_ATTRIBUTE \
 445     && (defined SHARED || defined LIBC_NONSHARED)
 446 # define attribute_hidden __attribute__ ((visibility ("hidden")))
 447 #else
 448 # define attribute_hidden
 449 #endif
 450
 451 #if defined HAVE_TLS_MODEL_ATTRIBUTE
 452 # define attribute_tls_model_ie __attribute__ ((tls_model ("initial-exec")))
 453 #else
 454 # define attribute_tls_model_ie
 455 #endif
 456
 457 /* Handling on non-exported internal names.  We have to do this only
 458    for shared code.  */
 459 #ifdef SHARED
 460 # define INTUSE(name) name##_internal
 461 # define INTDEF(name) strong_alias (name, name##_internal)
 462 # define INTVARDEF(name) \
 463   _INTVARDEF (name, name##_internal)
 464 # if defined HAVE_VISIBILITY_ATTRIBUTE
 465 #  define _INTVARDEF(name, aliasname) \
 466   extern __typeof (name) aliasname __attribute__ ((alias (#name), \
 467                                                    visibility ("hidden")));
 468 # else
 469 #  define _INTVARDEF(name, aliasname) \
 470   extern __typeof (name) aliasname __attribute__ ((alias (#name)));
 471 # endif
 472 # define INTDEF2(name, newname) strong_alias (name, newname##_internal)
 473 # define INTVARDEF2(name, newname) _INTVARDEF (name, newname##_internal)
 474 #else
 475 # define INTUSE(name) name
 476 # define INTDEF(name)
 477 # define INTVARDEF(name)
 478 # define INTDEF2(name, newname)
 479 # define INTVARDEF2(name, newname)
 480 #endif
 481
 482 /* The following macros are used for PLT bypassing within libc.so
 483    (and if needed other libraries similarly).
 484    First of all, you need to have the function prototyped somewhere,
 485    say in foo/foo.h:
 486
 487    int foo (int __bar);
 488
 489    If calls to foo within libc.so should always go to foo defined in libc.so,
 490    then in include/foo.h you add:
 491
 492    libc_hidden_proto (foo)
 493
 494    line and after the foo function definition:
 495
 496    int foo (int __bar)
 497    {
 498      return __bar;
 499    }
 500    libc_hidden_def (foo)
 501
 502    or
 503
 504    int foo (int __bar)
 505    {
 506      return __bar;
 507    }
 508    libc_hidden_weak (foo)
 509
 510    Simularly for global data. If references to foo within libc.so should
 511    always go to foo defined in libc.so, then in include/foo.h you add:
 512
 513    libc_hidden_proto (foo)
 514
 515    line and after foo's definition:
 516
 517    int foo = INITIAL_FOO_VALUE;
 518    libc_hidden_data_def (foo)
 519
 520    or
 521
 522    int foo = INITIAL_FOO_VALUE;
 523    libc_hidden_data_weak (foo)
 524
 525    If foo is normally just an alias (strong or weak) of some other function,
 526    you should use the normal strong_alias first, then add libc_hidden_def
 527    or libc_hidden_weak:
 528
 529    int baz (int __bar)
 530    {
 531      return __bar;
 532    }
 533    strong_alias (baz, foo)
 534    libc_hidden_weak (foo)
 535
 536    If the function should be internal to multiple objects, say ld.so and
 537    libc.so, the best way is to use:
 538
 539    #if !defined NOT_IN_libc || defined IS_IN_rtld
 540    hidden_proto (foo)
 541    #endif
 542
 543    in include/foo.h and the normal macros at all function definitions
 544    depending on what DSO they belong to.
 545
 546    If versioned_symbol macro is used to define foo,
 547    libc_hidden_ver macro should be used, as in:
 548
 549    int __real_foo (int __bar)
 550    {
 551      return __bar;
 552    }
 553    versioned_symbol (libc, __real_foo, foo, GLIBC_2_1);
 554    libc_hidden_ver (__real_foo, foo)  */
 555
 556 #if defined SHARED && defined DO_VERSIONING \
 557     && !defined HAVE_BROKEN_ALIAS_ATTRIBUTE && !defined NO_HIDDEN
 558 # ifndef __ASSEMBLER__
 559 #  if !defined HAVE_VISIBILITY_ATTRIBUTE \
 560       || defined HAVE_BROKEN_VISIBILITY_ATTRIBUTE
 561 #   define __hidden_proto_hiddenattr(attrs...)
 562 #  else
 563 #   define __hidden_proto_hiddenattr(attrs...) \
 564   __attribute__ ((visibility ("hidden"), ##attrs))
 565 #  endif
 566 #  define hidden_proto(name, attrs...) \
 567   __hidden_proto (name, __GI_##name, ##attrs)
 568 #  define __hidden_proto(name, internal, attrs...) \
 569   extern __typeof (name) internal; \
 570   extern __typeof (name) name __asm__ (__hidden_asmname (#internal)) \
 571   __hidden_proto_hiddenattr (attrs);
 572 #  define __hidden_asmname(name) \
 573   __hidden_asmname1 (__USER_LABEL_PREFIX__, name)
 574 #  define __hidden_asmname1(prefix, name) __hidden_asmname2(prefix, name)
 575 #  define __hidden_asmname2(prefix, name) #prefix name
 576 #  ifdef HAVE_ASM_SET_DIRECTIVE
 577 #   define __hidden_def1(original, alias)                       \
 578   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP       \
 579   .set C_SYMBOL_NAME (alias), C_SYMBOL_NAME (original)
 580 #   ifdef HAVE_ASM_GLOBAL_DOT_NAME
 581 #     define __hidden_dot_def1(original, alias)  ASM_LINE_SEP   \
 582   ASM_GLOBAL_DIRECTIVE C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP   \
 583   .set C_SYMBOL_DOT_NAME (alias), C_SYMBOL_DOT_NAME (original)
 584 #   else
 585 #     define __hidden_dot_def1(original, alias)
 586 #   endif
 587 #  else
 588 #   define __hidden_def1(original, alias)                       \
 589   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP       \
 590   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 591 #   ifdef HAVE_ASM_GLOBAL_DOT_NAME
 592 #    define __hidden_dot_def1(original, alias)  ASM_LINE_SEP    \
 593   ASM_GLOBAL_DIRECTIVE C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP   \
 594   C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original)
 595 #   else
 596 #    define __hidden_dot_def1(original, alias)
 597 #   endif
 598 #  endif
 599 #  define __hidden_def2(...) #__VA_ARGS__
 600 #  define __hidden_def3(...) __hidden_def2 (__VA_ARGS__)
 601 #  define hidden_def(name)                                      \
 602   __asm__ (__hidden_def3 (__hidden_def1 (__GI_##name, name) \
 603   __hidden_dot_def1 (__GI_##name, name)));
 604 #  define hidden_data_def(name)                                 \
 605   __asm__ (__hidden_def3 (__hidden_def1 (__GI_##name, name)));
 606 #  define hidden_ver(local, name)                               \
 607   __asm__ (__hidden_def3 (__hidden_def1 (local, __GI_##name) \
 608   __hidden_dot_def1 (local, __GI_##name)));
 609 #  define hidden_data_ver(local, name)                          \
 610   __asm__ (__hidden_def3 (__hidden_def1 (local, __GI_##name)));
 611 #  ifdef HAVE_WEAK_SYMBOLS
 612 #   ifdef HAVE_ASM_WEAKEXT_DIRECTIVE
 613 #    define __hidden_weak1(original, alias)                     \
 614   .weakext C_SYMBOL_NAME (alias), C_SYMBOL_NAME (original)
 615 #    ifdef HAVE_ASM_GLOBAL_DOT_NAME
 616 #     define __hidden_dot_weak1(original, alias)        ASM_LINE_SEP    \
 617   .weakext C_SYMBOL_DOT_NAME (alias), C_SYMBOL_DOT_NAME (original)
 618 #    else
 619 #     define __hidden_dot_weak1(original, alias)
 620 #    endif
 621 #   else /* ! HAVE_ASM_WEAKEXT_DIRECTIVE */
 622 #    define __hidden_weak1(original, alias)                     \
 623   .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP                      \
 624   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 625 #    ifdef HAVE_ASM_GLOBAL_DOT_NAME
 626 #     define __hidden_dot_weak1(original, alias)        ASM_LINE_SEP    \
 627   .weak C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP  \
 628   C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original)
 629 #    else
 630 #     define __hidden_dot_weak1(original, alias)
 631 #    endif
 632 #   endif
 633 #   define hidden_weak(name)                                    \
 634   __asm__ (__hidden_def3 (__hidden_weak1 (__GI_##name, name) \
 635   __hidden_dot_weak1 (__GI_##name, name)));
 636 #   define hidden_data_weak(name)                                       \
 637   __asm__ (__hidden_def3 (__hidden_weak1 (__GI_##name, name)));
 638 #  else
 639 #   define hidden_weak(name) hidden_def (name)
 640 #  endif
 641 # else
 642 /* For assembly, we need to do the opposite of what we do in C:
 643    in assembly gcc __REDIRECT stuff is not in place, so functions
 644    are defined by its normal name and we need to create the
 645    __GI_* alias to it, in C __REDIRECT causes the function definition
 646    to use __GI_* name and we need to add alias to the real name.
 647    There is no reason to use hidden_weak over hidden_def in assembly,
 648    but we provide it for consistency with the C usage.
 649    hidden_proto doesn't make sense for assembly but the equivalent
 650    is to call via the HIDDEN_JUMPTARGET macro instead of JUMPTARGET.  */
 651 #  define hidden_def(name)      strong_alias (name, __GI_##name)
 652 #  define hidden_weak(name)     hidden_def (name)
 653 #  define hidden_ver(local, name) strong_alias (local, __GI_##name)
 654 #  define hidden_data_def(name) strong_data_alias (name, __GI_##name)
 655 #  define hidden_data_weak(name)        hidden_data_def (name)
 656 #  define hidden_data_ver(local, name) strong_data_alias (local, __GI_##name)
 657 #  ifdef HAVE_ASM_GLOBAL_DOT_NAME
 658 #   define HIDDEN_JUMPTARGET(name) .__GI_##name
 659 #  else
 660 #   define HIDDEN_JUMPTARGET(name) __GI_##name
 661 #  endif
 662 # endif
 663 #else
 664 # ifndef __ASSEMBLER__
 665 #  define hidden_proto(name, attrs...)
 666 # else
 667 #  define HIDDEN_JUMPTARGET(name) JUMPTARGET(name)
 668 # endif /* Not  __ASSEMBLER__ */
 669 # define hidden_weak(name)
 670 # define hidden_def(name)
 671 # define hidden_ver(local, name)
 672 # define hidden_data_weak(name)
 673 # define hidden_data_def(name)
 674 # define hidden_data_ver(local, name)
 675 #endif
 676
 677 #if !defined NOT_IN_libc
 678 # define libc_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 679 # define libc_hidden_def(name) hidden_def (name)
 680 # define libc_hidden_weak(name) hidden_weak (name)
 681 # define libc_hidden_ver(local, name) hidden_ver (local, name)
 682 # define libc_hidden_data_def(name) hidden_data_def (name)
 683 # define libc_hidden_data_weak(name) hidden_data_weak (name)
 684 # define libc_hidden_data_ver(local, name) hidden_data_ver (local, name)
 685 #else
 686 # define libc_hidden_proto(name, attrs...)
 687 # define libc_hidden_def(name)
 688 # define libc_hidden_weak(name)
 689 # define libc_hidden_ver(local, name)
 690 # define libc_hidden_data_def(name)
 691 # define libc_hidden_data_weak(name)
 692 # define libc_hidden_data_ver(local, name)
 693 #endif
 694
 695 #if defined NOT_IN_libc && defined IS_IN_rtld
 696 # define rtld_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 697 # define rtld_hidden_def(name) hidden_def (name)
 698 # define rtld_hidden_weak(name) hidden_weak (name)
 699 # define rtld_hidden_ver(local, name) hidden_ver (local, name)
 700 # define rtld_hidden_data_def(name) hidden_data_def (name)
 701 # define rtld_hidden_data_weak(name) hidden_data_weak (name)
 702 # define rtld_hidden_data_ver(local, name) hidden_data_ver (local, name)
 703 #else
 704 # define rtld_hidden_proto(name, attrs...)
 705 # define rtld_hidden_def(name)
 706 # define rtld_hidden_weak(name)
 707 # define rtld_hidden_ver(local, name)
 708 # define rtld_hidden_data_def(name)
 709 # define rtld_hidden_data_weak(name)
 710 # define rtld_hidden_data_ver(local, name)
 711 #endif
 712
 713 #if defined NOT_IN_libc && defined IS_IN_libm
 714 # define libm_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 715 # define libm_hidden_def(name) hidden_def (name)
 716 # define libm_hidden_weak(name) hidden_weak (name)
 717 # define libm_hidden_ver(local, name) hidden_ver (local, name)
 718 # define libm_hidden_data_def(name) hidden_data_def (name)
 719 # define libm_hidden_data_weak(name) hidden_data_weak (name)
 720 # define libm_hidden_data_ver(local, name) hidden_data_ver (local, name)
 721 #else
 722 # define libm_hidden_proto(name, attrs...)
 723 # define libm_hidden_def(name)
 724 # define libm_hidden_weak(name)
 725 # define libm_hidden_ver(local, name)
 726 # define libm_hidden_data_def(name)
 727 # define libm_hidden_data_weak(name)
 728 # define libm_hidden_data_ver(local, name)
 729 #endif
 730
 731 #ifdef HAVE_BUILTIN_REDIRECTION
 732 # define libc_hidden_builtin_proto(name, attrs...) libc_hidden_proto (name, ##attrs)
 733 # define libc_hidden_builtin_def(name) libc_hidden_def (name)
 734 # define libc_hidden_builtin_weak(name) libc_hidden_weak (name)
 735 # define libc_hidden_builtin_ver(local, name) libc_hidden_ver (local, name)
 736 #else
 737 # define libc_hidden_builtin_proto(name, attrs...)
 738 # define libc_hidden_builtin_def(name)
 739 # define libc_hidden_builtin_weak(name)
 740 # define libc_hidden_builtin_ver(local, name)
 741 #endif
 742
 743 #endif /* libc-symbols.h */