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) 1995-2018 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, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef _LIBC_SYMBOLS_H
  21 #define _LIBC_SYMBOLS_H 1
  22
  23 /* This file is included implicitly in the compilation of every source file,
  24    using -include.  It includes config.h.  */
  25
  26 /* Enable declarations of GNU extensions, since we are compiling them.  */
  27 #define _GNU_SOURCE 1
  28
  29 #ifdef MODULE_NAME
  30
  31 /* Use `#if IS_IN (module)` to detect what component is being compiled.  */
  32 #define PASTE_NAME1(a,b) a##b
  33 #define PASTE_NAME(a,b)  PASTE_NAME1 (a,b)
  34 #define IN_MODULE        PASTE_NAME (MODULE_, MODULE_NAME)
  35 #define IS_IN(lib)       (IN_MODULE == MODULE_##lib)
  36
  37 /* True if the current module is a versioned library.  Versioned
  38    library names culled from shlib-versions files are assigned a
  39    MODULE_* value greater than MODULE_LIBS_BEGIN.  */
  40 #define IS_IN_LIB        (IN_MODULE > MODULE_LIBS_BEGIN)
  41
  42 /* The testsuite, and some other ancillary code, should be compiled against
  43    as close an approximation to the installed headers as possible.
  44    Defining this symbol disables most internal-use-only declarations
  45    provided by this header, and all those provided by other internal
  46    wrapper headers.  */
  47 #if IS_IN (testsuite) || defined IS_IN_build || defined __cplusplus
  48 # define _ISOMAC 1
  49 #endif
  50
  51 #else
  52 /* The generation process for a few files created very early in the
  53    build (notably libc-modules.h itself) involves preprocessing this
  54    header without defining MODULE_NAME.  Under these conditions,
  55    internal declarations (especially from config.h) must be visible,
  56    but IS_IN should always evaluate as false.  */
  57 # define IS_IN(lib) 0
  58 # define IS_IN_LIB 0
  59 # define IN_MODULE (-1)
  60 #endif
  61
  62 #ifndef _ISOMAC
  63
  64 /* This is defined for the compilation of all C library code.  features.h
  65    tests this to avoid inclusion of stubs.h while compiling the library,
  66    before stubs.h has been generated.  Some library code that is shared
  67    with other packages also tests this symbol to see if it is being
  68    compiled as part of the C library.  We must define this before including
  69    config.h, because it makes some definitions conditional on whether libc
  70    itself is being compiled, or just some generator program.  */
  71 #define _LIBC   1
  72
  73 /* Some files must be compiled with optimization on.  */
  74 #if !defined __ASSEMBLER__ && !defined __OPTIMIZE__
  75 # error "glibc cannot be compiled without optimization"
  76 #endif
  77
  78 /* -ffast-math cannot be applied to the C library, as it alters the ABI.
  79    Some test components that use -ffast-math are currently not part of
  80    IS_IN (testsuite) for technical reasons, so we have a secondary override.  */
  81 #if defined __FAST_MATH__ && !defined TEST_FAST_MATH
  82 # error "glibc must not be compiled with -ffast-math"
  83 #endif
  84
  85 #include <config.h>
  86
  87 /* When PIC is defined and SHARED isn't defined, we are building PIE
  88    by default.  */
  89 #if defined PIC && !defined SHARED
  90 # define BUILD_PIE_DEFAULT 1
  91 #else
  92 # define BUILD_PIE_DEFAULT 0
  93 #endif
  94
  95 /* Define this for the benefit of portable GNU code that wants to check it.
  96    Code that checks with #if will not #include <config.h> again, since we've
  97    already done it (and this file is implicitly included in every compile,
  98    via -include).  Code that checks with #ifdef will #include <config.h>,
  99    but that file should always be idempotent (i.e., it's just #define/#undef
 100    and nothing else anywhere should be changing the macro state it touches),
 101    so it's harmless.  */
 102 #define HAVE_CONFIG_H   0
 103
 104 /* Define these macros for the benefit of portable GNU code that wants to check
 105    them.  Of course, STDC_HEADERS is never false when building libc!  */
 106 #define STDC_HEADERS    1
 107 #define HAVE_MBSTATE_T  1
 108 #define HAVE_MBSRTOWCS  1
 109 #define HAVE_LIBINTL_H  1
 110 #define HAVE_WCTYPE_H   1
 111 #define HAVE_ISWCTYPE   1
 112 #define ENABLE_NLS      1
 113
 114 /* The symbols in all the user (non-_) macros are C symbols.  */
 115
 116 #ifndef __SYMBOL_PREFIX
 117 # define __SYMBOL_PREFIX
 118 #endif
 119
 120 #ifndef C_SYMBOL_NAME
 121 # define C_SYMBOL_NAME(name) name
 122 #endif
 123
 124 #ifndef ASM_LINE_SEP
 125 # define ASM_LINE_SEP ;
 126 #endif
 127
 128 #ifndef __ASSEMBLER__
 129 /* GCC understands weak symbols and aliases; use its interface where
 130    possible, instead of embedded assembly language.  */
 131
 132 /* Define ALIASNAME as a strong alias for NAME.  */
 133 # define strong_alias(name, aliasname) _strong_alias(name, aliasname)
 134 # define _strong_alias(name, aliasname) \
 135   extern __typeof (name) aliasname __attribute__ ((alias (#name)));
 136
 137 /* This comes between the return type and function name in
 138    a function definition to make that definition weak.  */
 139 # define weak_function __attribute__ ((weak))
 140 # define weak_const_function __attribute__ ((weak, __const__))
 141
 142 /* Define ALIASNAME as a weak alias for NAME.
 143    If weak aliases are not available, this defines a strong alias.  */
 144 # define weak_alias(name, aliasname) _weak_alias (name, aliasname)
 145 # define _weak_alias(name, aliasname) \
 146   extern __typeof (name) aliasname __attribute__ ((weak, alias (#name)));
 147
 148 /* Same as WEAK_ALIAS, but mark symbol as hidden.  */
 149 # define weak_hidden_alias(name, aliasname) \
 150   _weak_hidden_alias (name, aliasname)
 151 # define _weak_hidden_alias(name, aliasname) \
 152   extern __typeof (name) aliasname \
 153     __attribute__ ((weak, alias (#name), __visibility__ ("hidden")));
 154
 155 /* Declare SYMBOL as weak undefined symbol (resolved to 0 if not defined).  */
 156 # define weak_extern(symbol) _weak_extern (weak symbol)
 157 # define _weak_extern(expr) _Pragma (#expr)
 158
 159 /* In shared builds, the expression call_function_static_weak
 160    (FUNCTION-SYMBOL, ARGUMENTS) invokes FUNCTION-SYMBOL (an
 161    identifier) unconditionally, with the (potentially empty) argument
 162    list ARGUMENTS.  In static builds, if FUNCTION-SYMBOL has a
 163    definition, the function is invoked as before; if FUNCTION-SYMBOL
 164    is NULL, no call is performed.  */
 165 # ifdef SHARED
 166 #  define call_function_static_weak(func, ...) func (__VA_ARGS__)
 167 # else  /* !SHARED */
 168 #  define call_function_static_weak(func, ...)          \
 169   ({                                                    \
 170     extern __typeof__ (func) func weak_function;        \
 171     (func != NULL ? func (__VA_ARGS__) : (void)0);      \
 172   })
 173 # endif
 174
 175 #else /* __ASSEMBLER__ */
 176
 177 # ifdef HAVE_ASM_SET_DIRECTIVE
 178 #  define strong_alias(original, alias)                         \
 179   .globl C_SYMBOL_NAME (alias) ASM_LINE_SEP             \
 180   .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original)
 181 #  define strong_data_alias(original, alias) strong_alias(original, alias)
 182 # else
 183 #  define strong_alias(original, alias)                         \
 184   .globl C_SYMBOL_NAME (alias) ASM_LINE_SEP             \
 185   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 186 #  define strong_data_alias(original, alias) strong_alias(original, alias)
 187 # endif
 188
 189 # define weak_alias(original, alias)                                    \
 190   .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP                              \
 191   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 192
 193 # define weak_extern(symbol)                                            \
 194   .weak C_SYMBOL_NAME (symbol)
 195
 196 #endif /* __ASSEMBLER__ */
 197
 198 /* Determine the return address.  */
 199 #define RETURN_ADDRESS(nr) \
 200   __builtin_extract_return_addr (__builtin_return_address (nr))
 201
 202 /* When a reference to SYMBOL is encountered, the linker will emit a
 203    warning message MSG.  */
 204 /* We want the .gnu.warning.SYMBOL section to be unallocated.  */
 205 #define __make_section_unallocated(section_string)      \
 206   asm (".section " section_string "\n\t.previous");
 207
 208 /* Tacking on "\n\t#" to the section name makes gcc put it's bogus
 209    section attributes on what looks like a comment to the assembler.  */
 210 #ifdef HAVE_SECTION_QUOTES
 211 # define __sec_comment "\"\n\t#\""
 212 #else
 213 # define __sec_comment "\n\t#"
 214 #endif
 215 #define link_warning(symbol, msg) \
 216   __make_section_unallocated (".gnu.warning." #symbol) \
 217   static const char __evoke_link_warning_##symbol[]     \
 218     __attribute__ ((used, section (".gnu.warning." #symbol __sec_comment))) \
 219     = msg;
 220
 221 /* A canned warning for sysdeps/stub functions.  */
 222 #define stub_warning(name) \
 223   __make_section_unallocated (".gnu.glibc-stub." #name) \
 224   link_warning (name, #name " is not implemented and will always fail")
 225
 226 /* Warning for linking functions calling dlopen into static binaries.  */
 227 #ifdef SHARED
 228 #define static_link_warning(name)
 229 #else
 230 #define static_link_warning(name) static_link_warning1(name)
 231 #define static_link_warning1(name) \
 232   link_warning(name, "Using '" #name "' in statically linked applications \
 233 requires at runtime the shared libraries from the glibc version used \
 234 for linking")
 235 #endif
 236
 237 /* Resource Freeing Hooks:
 238
 239    Normally a process exits and the OS cleans up any allocated
 240    memory.  However, when tooling like mtrace or valgrind is monitoring
 241    the process we need to free all resources that are part of the
 242    process in order to provide the consistency required to track
 243    memory leaks.
 244
 245    A single public API exists and is __libc_freeres(), and this is used
 246    by applications like valgrind to freee resouces.
 247
 248    There are 3 cases:
 249
 250    (a) __libc_freeres
 251
 252         In this case all you need to do is define the freeing routine:
 253
 254         foo.c:
 255         libfoo_freeres_fn (foo_freeres)
 256         {
 257           complex_free (mem);
 258         }
 259
 260         This ensures the function is called at the right point to free
 261         resources.
 262
 263    (b) __libc_freeres_ptr
 264
 265         The framework for (a) iterates over the list of pointers-to-free
 266         in (b) and frees them.
 267
 268         foo.c:
 269         libc_freeres_ptr (static char *foo_buffer);
 270
 271         Freeing these resources alaways happens last and is equivalent
 272         to registering a function that does 'free (foo_buffer)'.
 273
 274    (c) Explicit lists of free routines to call or objects to free.
 275
 276         It is the intended goal to remove (a) and (b) which have some
 277         non-determinism based on link order, and instead use explicit
 278         lists of functions and frees to resolve cleanup ordering issues
 279         and make it easy to debug and maintain.
 280
 281         As of today the following subsystems use (c):
 282
 283         Per-thread cleanup:
 284         * malloc/thread-freeres.c
 285
 286         libdl cleanup:
 287         * dlfcn/dlfreeres.c
 288
 289         libpthread cleanup:
 290         * nptl/nptlfreeres.c
 291
 292         So if you need any shutdown routines to run you should add them
 293         directly to the appropriate subsystem's shutdown list.  */
 294
 295 /* Resource pointers to free in libc.so.  */
 296 #define libc_freeres_ptr(decl) \
 297   __make_section_unallocated ("__libc_freeres_ptrs, \"aw\", %nobits") \
 298   decl __attribute__ ((section ("__libc_freeres_ptrs" __sec_comment)))
 299
 300 /* Resource freeing functions from libc.so go in this section.  */
 301 #define __libc_freeres_fn_section \
 302   __attribute__ ((section ("__libc_freeres_fn")))
 303
 304 /* Resource freeing functions for libc.so.  */
 305 #define libc_freeres_fn(name) \
 306   static void name (void) __attribute_used__ __libc_freeres_fn_section; \
 307   text_set_element (__libc_subfreeres, name);                           \
 308   static void name (void)
 309
 310 /* Declare SYMBOL to be TYPE (`function' or `object') of SIZE bytes
 311    alias to ORIGINAL, when the assembler supports such declarations
 312    (such as in ELF).
 313    This is only necessary when defining something in assembly, or playing
 314    funny alias games where the size should be other than what the compiler
 315    thinks it is.  */
 316 #define declare_symbol_alias(symbol, original, type, size) \
 317   declare_symbol_alias_1 (symbol, original, type, size)
 318 #ifdef __ASSEMBLER__
 319 # define declare_symbol_alias_1(symbol, original, type, size) \
 320    strong_alias (original, symbol); \
 321    .type C_SYMBOL_NAME (symbol), %##type; \
 322    .size C_SYMBOL_NAME (symbol), size
 323 #else /* Not __ASSEMBLER__.  */
 324 # define declare_symbol_alias_1(symbol, original, type, size) \
 325    asm (".globl " __SYMBOL_PREFIX #symbol \
 326         "\n\t" declare_symbol_alias_1_alias (symbol, original) \
 327         "\n\t.type " __SYMBOL_PREFIX #symbol ", " \
 328         "%" #type \
 329         "\n\t.size " __SYMBOL_PREFIX #symbol ", " #size);
 330 # ifdef HAVE_ASM_SET_DIRECTIVE
 331 #  define declare_symbol_alias_1_alias(symbol, original) \
 332      ".set " __SYMBOL_PREFIX #symbol ", " __SYMBOL_PREFIX #original
 333 # else
 334 #  define declare_symbol_alias_1_alias(symbol, original) \
 335      __SYMBOL_PREFIX #symbol " = " __SYMBOL_PREFIX #original
 336 # endif /* HAVE_ASM_SET_DIRECTIVE */
 337 #endif /* __ASSEMBLER__ */
 338
 339
 340 /*
 341 \f
 342 */
 343
 344 /* Symbol set support macros.  */
 345
 346 /* Make SYMBOL, which is in the text segment, an element of SET.  */
 347 #define text_set_element(set, symbol)   _elf_set_element(set, symbol)
 348 /* Make SYMBOL, which is in the data segment, an element of SET.  */
 349 #define data_set_element(set, symbol)   _elf_set_element(set, symbol)
 350 /* Make SYMBOL, which is in the bss segment, an element of SET.  */
 351 #define bss_set_element(set, symbol)    _elf_set_element(set, symbol)
 352
 353 /* These are all done the same way in ELF.
 354    There is a new section created for each set.  */
 355 #ifdef SHARED
 356 /* When building a shared library, make the set section writable,
 357    because it will need to be relocated at run time anyway.  */
 358 # define _elf_set_element(set, symbol) \
 359   static const void *__elf_set_##set##_element_##symbol##__ \
 360     __attribute__ ((used, section (#set))) = &(symbol)
 361 #else
 362 # define _elf_set_element(set, symbol) \
 363   static const void *const __elf_set_##set##_element_##symbol##__ \
 364     __attribute__ ((used, section (#set))) = &(symbol)
 365 #endif
 366
 367 /* Define SET as a symbol set.  This may be required (it is in a.out) to
 368    be able to use the set's contents.  */
 369 #define symbol_set_define(set)  symbol_set_declare(set)
 370
 371 /* Declare SET for use in this module, if defined in another module.
 372    In a shared library, this is always local to that shared object.
 373    For static linking, the set might be wholly absent and so we use
 374    weak references.  */
 375 #define symbol_set_declare(set) \
 376   extern char const __start_##set[] __symbol_set_attribute; \
 377   extern char const __stop_##set[] __symbol_set_attribute;
 378 #ifdef SHARED
 379 # define __symbol_set_attribute attribute_hidden
 380 #else
 381 # define __symbol_set_attribute __attribute__ ((weak))
 382 #endif
 383
 384 /* Return a pointer (void *const *) to the first element of SET.  */
 385 #define symbol_set_first_element(set)   ((void *const *) (&__start_##set))
 386
 387 /* Return true iff PTR (a void *const *) has been incremented
 388    past the last element in SET.  */
 389 #define symbol_set_end_p(set, ptr) ((ptr) >= (void *const *) &__stop_##set)
 390
 391 /* Use symbol_version_reference to specify the version a symbol
 392    reference should link to.  Use symbol_version or
 393    default_symbol_version for the definition of a versioned symbol.
 394    The difference is that the latter is a no-op in non-shared
 395    builds.  */
 396 #ifdef __ASSEMBLER__
 397 # define symbol_version_reference(real, name, version) \
 398      .symver real, name##@##version
 399 #else  /* !__ASSEMBLER__ */
 400 # define symbol_version_reference(real, name, version) \
 401   __asm__ (".symver " #real "," #name "@" #version)
 402 #endif
 403
 404 #ifdef SHARED
 405 # define symbol_version(real, name, version) \
 406   symbol_version_reference(real, name, version)
 407 # define default_symbol_version(real, name, version) \
 408      _default_symbol_version(real, name, version)
 409 # ifdef __ASSEMBLER__
 410 #  define _default_symbol_version(real, name, version) \
 411      .symver real, name##@##@##version
 412 # else
 413 #  define _default_symbol_version(real, name, version) \
 414      __asm__ (".symver " #real "," #name "@@" #version)
 415 # endif
 416 #else
 417 # define symbol_version(real, name, version)
 418 # define default_symbol_version(real, name, version) \
 419   strong_alias(real, name)
 420 #endif
 421
 422 #if defined SHARED || defined LIBC_NONSHARED \
 423   || (BUILD_PIE_DEFAULT && IS_IN (libc))
 424 # define attribute_hidden __attribute__ ((visibility ("hidden")))
 425 #else
 426 # define attribute_hidden
 427 #endif
 428
 429 #define attribute_tls_model_ie __attribute__ ((tls_model ("initial-exec")))
 430
 431 #define attribute_relro __attribute__ ((section (".data.rel.ro")))
 432
 433
 434 /* Used to disable stack protection in sensitive places, like ifunc
 435    resolvers and early static TLS init.  */
 436 #ifdef HAVE_CC_NO_STACK_PROTECTOR
 437 # define inhibit_stack_protector \
 438     __attribute__ ((__optimize__ ("-fno-stack-protector")))
 439 #else
 440 # define inhibit_stack_protector
 441 #endif
 442
 443 /* The following macros are used for PLT bypassing within libc.so
 444    (and if needed other libraries similarly).
 445    First of all, you need to have the function prototyped somewhere,
 446    say in foo/foo.h:
 447
 448    int foo (int __bar);
 449
 450    If calls to foo within libc.so should always go to foo defined in libc.so,
 451    then in include/foo.h you add:
 452
 453    libc_hidden_proto (foo)
 454
 455    line and after the foo function definition:
 456
 457    int foo (int __bar)
 458    {
 459      return __bar;
 460    }
 461    libc_hidden_def (foo)
 462
 463    or
 464
 465    int foo (int __bar)
 466    {
 467      return __bar;
 468    }
 469    libc_hidden_weak (foo)
 470
 471    Similarly for global data.  If references to foo within libc.so should
 472    always go to foo defined in libc.so, then in include/foo.h you add:
 473
 474    libc_hidden_proto (foo)
 475
 476    line and after foo's definition:
 477
 478    int foo = INITIAL_FOO_VALUE;
 479    libc_hidden_data_def (foo)
 480
 481    or
 482
 483    int foo = INITIAL_FOO_VALUE;
 484    libc_hidden_data_weak (foo)
 485
 486    If foo is normally just an alias (strong or weak) to some other function,
 487    you should use the normal strong_alias first, then add libc_hidden_def
 488    or libc_hidden_weak:
 489
 490    int baz (int __bar)
 491    {
 492      return __bar;
 493    }
 494    strong_alias (baz, foo)
 495    libc_hidden_weak (foo)
 496
 497    If the function should be internal to multiple objects, say ld.so and
 498    libc.so, the best way is to use:
 499
 500    #if IS_IN (libc) || IS_IN (rtld)
 501    hidden_proto (foo)
 502    #endif
 503
 504    in include/foo.h and the normal macros at all function definitions
 505    depending on what DSO they belong to.
 506
 507    If versioned_symbol macro is used to define foo,
 508    libc_hidden_ver macro should be used, as in:
 509
 510    int __real_foo (int __bar)
 511    {
 512      return __bar;
 513    }
 514    versioned_symbol (libc, __real_foo, foo, GLIBC_2_1);
 515    libc_hidden_ver (__real_foo, foo)  */
 516
 517 #if defined SHARED && !defined NO_HIDDEN
 518 # ifndef __ASSEMBLER__
 519 #  define __hidden_proto_hiddenattr(attrs...) \
 520   __attribute__ ((visibility ("hidden"), ##attrs))
 521 #  define hidden_proto(name, attrs...) \
 522   __hidden_proto (name, , __GI_##name, ##attrs)
 523 #  define hidden_tls_proto(name, attrs...) \
 524   __hidden_proto (name, __thread, __GI_##name, ##attrs)
 525 #  define __hidden_proto(name, thread, internal, attrs...)           \
 526   extern thread __typeof (name) name __asm__ (__hidden_asmname (#internal)) \
 527   __hidden_proto_hiddenattr (attrs);
 528 #  define __hidden_asmname(name) \
 529   __hidden_asmname1 (__USER_LABEL_PREFIX__, name)
 530 #  define __hidden_asmname1(prefix, name) __hidden_asmname2(prefix, name)
 531 #  define __hidden_asmname2(prefix, name) #prefix name
 532 #  define __hidden_ver1(local, internal, name) \
 533   extern __typeof (name) __EI_##name __asm__(__hidden_asmname (#internal)); \
 534   extern __typeof (name) __EI_##name \
 535         __attribute__((alias (__hidden_asmname (#local))))
 536 #  define hidden_ver(local, name)       __hidden_ver1(local, __GI_##name, name);
 537 #  define hidden_data_ver(local, name)  hidden_ver(local, name)
 538 #  define hidden_def(name)              __hidden_ver1(__GI_##name, name, name);
 539 #  define hidden_data_def(name)         hidden_def(name)
 540 #  define hidden_weak(name) \
 541         __hidden_ver1(__GI_##name, name, name) __attribute__((weak));
 542 #  define hidden_data_weak(name)        hidden_weak(name)
 543 #  define hidden_nolink(name, lib, version) \
 544   __hidden_nolink1 (__GI_##name, __EI_##name, name, VERSION_##lib##_##version)
 545 #  define __hidden_nolink1(local, internal, name, version) \
 546   __hidden_nolink2 (local, internal, name, version)
 547 #  define __hidden_nolink2(local, internal, name, version) \
 548   extern __typeof (name) internal __attribute__ ((alias (#local))); \
 549   __hidden_nolink3 (local, internal, #name "@" #version)
 550 #  define __hidden_nolink3(local, internal, vername) \
 551   __asm__ (".symver " #internal ", " vername);
 552 # else
 553 /* For assembly, we need to do the opposite of what we do in C:
 554    in assembly gcc __REDIRECT stuff is not in place, so functions
 555    are defined by its normal name and we need to create the
 556    __GI_* alias to it, in C __REDIRECT causes the function definition
 557    to use __GI_* name and we need to add alias to the real name.
 558    There is no reason to use hidden_weak over hidden_def in assembly,
 559    but we provide it for consistency with the C usage.
 560    hidden_proto doesn't make sense for assembly but the equivalent
 561    is to call via the HIDDEN_JUMPTARGET macro instead of JUMPTARGET.  */
 562 #  define hidden_def(name)      strong_alias (name, __GI_##name)
 563 #  define hidden_weak(name)     hidden_def (name)
 564 #  define hidden_ver(local, name) strong_alias (local, __GI_##name)
 565 #  define hidden_data_def(name) strong_data_alias (name, __GI_##name)
 566 #  define hidden_data_weak(name)        hidden_data_def (name)
 567 #  define hidden_data_ver(local, name) strong_data_alias (local, __GI_##name)
 568 #  define HIDDEN_JUMPTARGET(name) __GI_##name
 569 # endif
 570 #else
 571 # ifndef __ASSEMBLER__
 572 #  if !defined SHARED && IS_IN (libc) && !defined LIBC_NONSHARED \
 573       && (!defined PIC || !defined NO_HIDDEN_EXTERN_FUNC_IN_PIE) \
 574       && !defined NO_HIDDEN
 575 #   define __hidden_proto_hiddenattr(attrs...) \
 576   __attribute__ ((visibility ("hidden"), ##attrs))
 577 #   define hidden_proto(name, attrs...) \
 578   __hidden_proto (name, , name, ##attrs)
 579 #   define hidden_tls_proto(name, attrs...) \
 580   __hidden_proto (name, __thread, name, ##attrs)
 581 #  define __hidden_proto(name, thread, internal, attrs...)           \
 582   extern thread __typeof (name) name __hidden_proto_hiddenattr (attrs);
 583 # else
 584 #   define hidden_proto(name, attrs...)
 585 #   define hidden_tls_proto(name, attrs...)
 586 # endif
 587 # else
 588 #  define HIDDEN_JUMPTARGET(name) JUMPTARGET(name)
 589 # endif /* Not  __ASSEMBLER__ */
 590 # define hidden_weak(name)
 591 # define hidden_def(name)
 592 # define hidden_ver(local, name)
 593 # define hidden_data_weak(name)
 594 # define hidden_data_def(name)
 595 # define hidden_data_ver(local, name)
 596 # define hidden_nolink(name, lib, version)
 597 #endif
 598
 599 #if IS_IN (libc)
 600 # define libc_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 601 # define libc_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
 602 # define libc_hidden_def(name) hidden_def (name)
 603 # define libc_hidden_weak(name) hidden_weak (name)
 604 # ifdef LINK_OBSOLETE_RPC
 605    /* libc_hidden_nolink_sunrpc should only get used in sunrpc code.  */
 606 #  define libc_hidden_nolink_sunrpc(name, version) hidden_def (name)
 607 # else
 608 #  define libc_hidden_nolink_sunrpc(name, version) hidden_nolink (name, libc, version)
 609 # endif
 610 # define libc_hidden_ver(local, name) hidden_ver (local, name)
 611 # define libc_hidden_data_def(name) hidden_data_def (name)
 612 # define libc_hidden_data_weak(name) hidden_data_weak (name)
 613 # define libc_hidden_data_ver(local, name) hidden_data_ver (local, name)
 614 #else
 615 # define libc_hidden_proto(name, attrs...)
 616 # define libc_hidden_tls_proto(name, attrs...)
 617 # define libc_hidden_def(name)
 618 # define libc_hidden_weak(name)
 619 # define libc_hidden_ver(local, name)
 620 # define libc_hidden_data_def(name)
 621 # define libc_hidden_data_weak(name)
 622 # define libc_hidden_data_ver(local, name)
 623 #endif
 624
 625 #if IS_IN (rtld) && !defined NO_RTLD_HIDDEN
 626 # define rtld_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 627 # define rtld_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
 628 # define rtld_hidden_def(name) hidden_def (name)
 629 # define rtld_hidden_weak(name) hidden_weak (name)
 630 # define rtld_hidden_ver(local, name) hidden_ver (local, name)
 631 # define rtld_hidden_data_def(name) hidden_data_def (name)
 632 # define rtld_hidden_data_weak(name) hidden_data_weak (name)
 633 # define rtld_hidden_data_ver(local, name) hidden_data_ver (local, name)
 634 #else
 635 # define rtld_hidden_proto(name, attrs...)
 636 # define rtld_hidden_tls_proto(name, attrs...)
 637 # define rtld_hidden_def(name)
 638 # define rtld_hidden_weak(name)
 639 # define rtld_hidden_ver(local, name)
 640 # define rtld_hidden_data_def(name)
 641 # define rtld_hidden_data_weak(name)
 642 # define rtld_hidden_data_ver(local, name)
 643 #endif
 644
 645 #if IS_IN (libm)
 646 # define libm_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 647 # define libm_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
 648 # define libm_hidden_def(name) hidden_def (name)
 649 # define libm_hidden_weak(name) hidden_weak (name)
 650 # define libm_hidden_ver(local, name) hidden_ver (local, name)
 651 # define libm_hidden_data_def(name) hidden_data_def (name)
 652 # define libm_hidden_data_weak(name) hidden_data_weak (name)
 653 # define libm_hidden_data_ver(local, name) hidden_data_ver (local, name)
 654 #else
 655 # define libm_hidden_proto(name, attrs...)
 656 # define libm_hidden_tls_proto(name, attrs...)
 657 # define libm_hidden_def(name)
 658 # define libm_hidden_weak(name)
 659 # define libm_hidden_ver(local, name)
 660 # define libm_hidden_data_def(name)
 661 # define libm_hidden_data_weak(name)
 662 # define libm_hidden_data_ver(local, name)
 663 #endif
 664
 665 #if IS_IN (libmvec)
 666 # define libmvec_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 667 # define libmvec_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
 668 # define libmvec_hidden_def(name) hidden_def (name)
 669 # define libmvec_hidden_weak(name) hidden_weak (name)
 670 # define libmvec_hidden_ver(local, name) hidden_ver (local, name)
 671 # define libmvec_hidden_data_def(name) hidden_data_def (name)
 672 # define libmvec_hidden_data_weak(name) hidden_data_weak (name)
 673 # define libmvec_hidden_data_ver(local, name) hidden_data_ver (local, name)
 674 #else
 675 # define libmvec_hidden_proto(name, attrs...)
 676 # define libmvec_hidden_tls_proto(name, attrs...)
 677 # define libmvec_hidden_def(name)
 678 # define libmvec_hidden_weak(name)
 679 # define libmvec_hidden_ver(local, name)
 680 # define libmvec_hidden_data_def(name)
 681 # define libmvec_hidden_data_weak(name)
 682 # define libmvec_hidden_data_ver(local, name)
 683 #endif
 684
 685 #if IS_IN (libresolv)
 686 # define libresolv_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 687 # define libresolv_hidden_tls_proto(name, attrs...) \
 688   hidden_tls_proto (name, ##attrs)
 689 # define libresolv_hidden_def(name) hidden_def (name)
 690 # define libresolv_hidden_weak(name) hidden_weak (name)
 691 # define libresolv_hidden_ver(local, name) hidden_ver (local, name)
 692 # define libresolv_hidden_data_def(name) hidden_data_def (name)
 693 # define libresolv_hidden_data_weak(name) hidden_data_weak (name)
 694 # define libresolv_hidden_data_ver(local, name) hidden_data_ver (local, name)
 695 #else
 696 # define libresolv_hidden_proto(name, attrs...)
 697 # define libresolv_hidden_tls_proto(name, attrs...)
 698 # define libresolv_hidden_def(name)
 699 # define libresolv_hidden_weak(name)
 700 # define libresolv_hidden_ver(local, name)
 701 # define libresolv_hidden_data_def(name)
 702 # define libresolv_hidden_data_weak(name)
 703 # define libresolv_hidden_data_ver(local, name)
 704 #endif
 705
 706 #if IS_IN (librt)
 707 # define librt_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 708 # define librt_hidden_tls_proto(name, attrs...) \
 709   hidden_tls_proto (name, ##attrs)
 710 # define librt_hidden_def(name) hidden_def (name)
 711 # define librt_hidden_weak(name) hidden_weak (name)
 712 # define librt_hidden_ver(local, name) hidden_ver (local, name)
 713 # define librt_hidden_data_def(name) hidden_data_def (name)
 714 # define librt_hidden_data_weak(name) hidden_data_weak (name)
 715 # define librt_hidden_data_ver(local, name) hidden_data_ver (local, name)
 716 #else
 717 # define librt_hidden_proto(name, attrs...)
 718 # define librt_hidden_tls_proto(name, attrs...)
 719 # define librt_hidden_def(name)
 720 # define librt_hidden_weak(name)
 721 # define librt_hidden_ver(local, name)
 722 # define librt_hidden_data_def(name)
 723 # define librt_hidden_data_weak(name)
 724 # define librt_hidden_data_ver(local, name)
 725 #endif
 726
 727 #if IS_IN (libdl)
 728 # define libdl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 729 # define libdl_hidden_tls_proto(name, attrs...) \
 730   hidden_tls_proto (name, ##attrs)
 731 # define libdl_hidden_def(name) hidden_def (name)
 732 # define libdl_hidden_weak(name) hidden_weak (name)
 733 # define libdl_hidden_ver(local, name) hidden_ver (local, name)
 734 # define libdl_hidden_data_def(name) hidden_data_def (name)
 735 # define libdl_hidden_data_weak(name) hidden_data_weak (name)
 736 # define libdl_hidden_data_ver(local, name) hidden_data_ver (local, name)
 737 #else
 738 # define libdl_hidden_proto(name, attrs...)
 739 # define libdl_hidden_tls_proto(name, attrs...)
 740 # define libdl_hidden_def(name)
 741 # define libdl_hidden_weak(name)
 742 # define libdl_hidden_ver(local, name)
 743 # define libdl_hidden_data_def(name)
 744 # define libdl_hidden_data_weak(name)
 745 # define libdl_hidden_data_ver(local, name)
 746 #endif
 747
 748 #if IS_IN (libnss_files)
 749 # define libnss_files_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 750 # define libnss_files_hidden_tls_proto(name, attrs...) \
 751   hidden_tls_proto (name, ##attrs)
 752 # define libnss_files_hidden_def(name) hidden_def (name)
 753 # define libnss_files_hidden_weak(name) hidden_weak (name)
 754 # define libnss_files_hidden_ver(local, name) hidden_ver (local, name)
 755 # define libnss_files_hidden_data_def(name) hidden_data_def (name)
 756 # define libnss_files_hidden_data_weak(name) hidden_data_weak (name)
 757 # define libnss_files_hidden_data_ver(local, name) hidden_data_ver(local, name)
 758 #else
 759 # define libnss_files_hidden_proto(name, attrs...)
 760 # define libnss_files_hidden_tls_proto(name, attrs...)
 761 # define libnss_files_hidden_def(name)
 762 # define libnss_files_hidden_weak(name)
 763 # define libnss_files_hidden_ver(local, name)
 764 # define libnss_files_hidden_data_def(name)
 765 # define libnss_files_hidden_data_weak(name)
 766 # define libnss_files_hidden_data_ver(local, name)
 767 #endif
 768
 769 #if IS_IN (libnsl)
 770 # define libnsl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 771 # define libnsl_hidden_tls_proto(name, attrs...) \
 772   hidden_tls_proto (name, ##attrs)
 773 # ifdef LINK_OBSOLETE_NSL
 774    /* libnsl_hidden_nolink should only get used in libnsl code.  */
 775 #  define libnsl_hidden_nolink_def(name, version) libnsl_hidden_def (name)
 776 # else
 777 #  define libnsl_hidden_nolink_def(name, version) hidden_nolink (name, libnsl, version)
 778 # endif
 779 # define libnsl_hidden_def(name) hidden_def (name)
 780 # define libnsl_hidden_weak(name) hidden_weak (name)
 781 # define libnsl_hidden_ver(local, name) hidden_ver (local, name)
 782 # define libnsl_hidden_data_def(name) hidden_data_def (name)
 783 # define libnsl_hidden_data_weak(name) hidden_data_weak (name)
 784 # define libnsl_hidden_data_ver(local, name) hidden_data_ver (local, name)
 785 #else
 786 # define libnsl_hidden_proto(name, attrs...)
 787 # define libnsl_hidden_tls_proto(name, attrs...)
 788 # define libnsl_hidden_def(name)
 789 # define libnsl_hidden_weak(name)
 790 # define libnsl_hidden_ver(local, name)
 791 # define libnsl_hidden_data_def(name)
 792 # define libnsl_hidden_data_weak(name)
 793 # define libnsl_hidden_data_ver(local, name)
 794 #endif
 795
 796 #if IS_IN (libnss_nisplus)
 797 # define libnss_nisplus_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 798 # define libnss_nisplus_hidden_tls_proto(name, attrs...) \
 799   hidden_tls_proto (name, ##attrs)
 800 # define libnss_nisplus_hidden_def(name) hidden_def (name)
 801 # define libnss_nisplus_hidden_weak(name) hidden_weak (name)
 802 # define libnss_nisplus_hidden_ver(local, name) hidden_ver (local, name)
 803 # define libnss_nisplus_hidden_data_def(name) hidden_data_def (name)
 804 # define libnss_nisplus_hidden_data_weak(name) hidden_data_weak (name)
 805 # define libnss_nisplus_hidden_data_ver(local, name) hidden_data_ver (local, name)
 806 #else
 807 # define libnss_nisplus_hidden_proto(name, attrs...)
 808 # define libnss_nisplus_hidden_tls_proto(name, attrs...)
 809 # define libnss_nisplus_hidden_def(name)
 810 # define libnss_nisplus_hidden_weak(name)
 811 # define libnss_nisplus_hidden_ver(local, name)
 812 # define libnss_nisplus_hidden_data_def(name)
 813 # define libnss_nisplus_hidden_data_weak(name)
 814 # define libnss_nisplus_hidden_data_ver(local, name)
 815 #endif
 816
 817 #define libc_hidden_builtin_proto(name, attrs...) libc_hidden_proto (name, ##attrs)
 818 #define libc_hidden_builtin_def(name) libc_hidden_def (name)
 819 #define libc_hidden_builtin_weak(name) libc_hidden_weak (name)
 820 #define libc_hidden_builtin_ver(local, name) libc_hidden_ver (local, name)
 821 #ifdef __ASSEMBLER__
 822 # define HIDDEN_BUILTIN_JUMPTARGET(name) HIDDEN_JUMPTARGET(name)
 823 #endif
 824
 825 #if IS_IN (libutil)
 826 # define libutil_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 827 # define libutil_hidden_tls_proto(name, attrs...) \
 828   hidden_tls_proto (name, ##attrs)
 829 # define libutil_hidden_def(name) hidden_def (name)
 830 # define libutil_hidden_weak(name) hidden_weak (name)
 831 # define libutil_hidden_ver(local, name) hidden_ver (local, name)
 832 # define libutil_hidden_data_def(name) hidden_data_def (name)
 833 # define libutil_hidden_data_weak(name) hidden_data_weak (name)
 834 # define libutil_hidden_data_ver(local, name) hidden_data_ver (local, name)
 835 #else
 836 # define libutil_hidden_proto(name, attrs...)
 837 # define libutil_hidden_tls_proto(name, attrs...)
 838 # define libutil_hidden_def(name)
 839 # define libutil_hidden_weak(name)
 840 # define libutil_hidden_ver(local, name)
 841 # define libutil_hidden_data_def(name)
 842 # define libutil_hidden_data_weak(name)
 843 # define libutil_hidden_data_ver(local, name)
 844 #endif
 845
 846 /* Get some dirty hacks.  */
 847 #include <symbol-hacks.h>
 848
 849 /* Move compatibility symbols out of the way by placing them all in a
 850    special section.  */
 851 #ifndef __ASSEMBLER__
 852 # define attribute_compat_text_section \
 853     __attribute__ ((section (".text.compat")))
 854 # define attribute_compat_data_section \
 855     __attribute__ ((section (".data.compat")))
 856 #else
 857 # define compat_text_section .section ".text.compat", "ax";
 858 # define compat_data_section .section ".data.compat", "aw";
 859 #endif
 860
 861 /* Helper / base  macros for indirect function symbols.  */
 862 #define __ifunc_resolver(type_name, name, expr, arg, init, classifier)  \
 863   classifier inhibit_stack_protector                                    \
 864   __typeof (type_name) *name##_ifunc (arg)                              \
 865   {                                                                     \
 866     init ();                                                            \
 867     __typeof (type_name) *res = expr;                                   \
 868     return res;                                                         \
 869   }
 870
 871 #ifdef HAVE_GCC_IFUNC
 872 # define __ifunc(type_name, name, expr, arg, init)                      \
 873   extern __typeof (type_name) name __attribute__                        \
 874                               ((ifunc (#name "_ifunc")));               \
 875   __ifunc_resolver (type_name, name, expr, arg, init, static)
 876
 877 # define __ifunc_hidden(type_name, name, expr, arg, init)       \
 878   __ifunc (type_name, name, expr, arg, init)
 879 #else
 880 /* Gcc does not support __attribute__ ((ifunc (...))).  Use the old behaviour
 881    as fallback.  But keep in mind that the debug information for the ifunc
 882    resolver functions is not correct.  It contains the ifunc'ed function as
 883    DW_AT_linkage_name.  E.g. lldb uses this field and an inferior function
 884    call of the ifunc'ed function will fail due to "no matching function for
 885    call to ..." because the ifunc'ed function and the resolver function have
 886    different signatures.  (Gcc support is disabled at least on a ppc64le
 887    Ubuntu 14.04 system.)  */
 888
 889 # define __ifunc(type_name, name, expr, arg, init)                      \
 890   extern __typeof (type_name) name;                                     \
 891   __typeof (type_name) *name##_ifunc (arg) __asm__ (#name);             \
 892   __ifunc_resolver (type_name, name, expr, arg, init,)                  \
 893  __asm__ (".type " #name ", %gnu_indirect_function");
 894
 895 # define __ifunc_hidden(type_name, name, expr, arg, init)               \
 896   extern __typeof (type_name) __libc_##name;                            \
 897   __ifunc (type_name, __libc_##name, expr, arg, init)                   \
 898   strong_alias (__libc_##name, name);
 899 #endif /* !HAVE_GCC_IFUNC  */
 900
 901 /* The following macros are used for indirect function symbols in libc.so.
 902    First of all, you need to have the function prototyped somewhere,
 903    say in foo.h:
 904
 905    int foo (int __bar);
 906
 907    If you have an implementation for foo which e.g. uses a special hardware
 908    feature which isn't available on all machines where this libc.so will be
 909    used but decideable if available at runtime e.g. via hwcaps, you can provide
 910    two or multiple implementations of foo:
 911
 912    int __foo_default (int __bar)
 913    {
 914      return __bar;
 915    }
 916
 917    int __foo_special (int __bar)
 918    {
 919      return __bar;
 920    }
 921
 922    If your function foo has no libc_hidden_proto (foo) defined for PLT
 923    bypassing, you can use:
 924
 925    #define INIT_ARCH() unsigned long int hwcap = __GLRO(dl_hwcap);
 926
 927    libc_ifunc (foo, (hwcap & HWCAP_SPECIAL) ? __foo_special : __foo_default);
 928
 929    This will define a resolver function for foo which returns __foo_special or
 930    __foo_default depending on your specified expression.  Please note that you
 931    have to define a macro function INIT_ARCH before using libc_ifunc macro as
 932    it is called by the resolver function before evaluating the specified
 933    expression.  In this example it is used to prepare the hwcap variable.
 934    The resolver function is assigned to an ifunc'ed symbol foo.  Calls to foo
 935    from inside or outside of libc.so will be indirected by a PLT call.
 936
 937    If your function foo has a libc_hidden_proto (foo) defined for PLT bypassing
 938    and calls to foo within libc.so should always go to one specific
 939    implementation of foo e.g. __foo_default then you have to add:
 940
 941    __hidden_ver1 (__foo_default, __GI_foo, __foo_default);
 942
 943    or a tweaked definition of libc_hidden_def macro after the __foo_default
 944    function definition.  Calls to foo within libc.so will always go directly to
 945    __foo_default.  Calls to foo from outside libc.so will be indirected by a
 946    PLT call to ifunc'ed symbol foo which you have to define in a separate
 947    compile unit:
 948
 949    #define foo __redirect_foo
 950    #include <foo.h>
 951    #undef foo
 952
 953    extern __typeof (__redirect_foo) __foo_default attribute_hidden;
 954    extern __typeof (__redirect_foo) __foo_special attribute_hidden;
 955
 956    libc_ifunc_redirected (__redirect_foo, foo,
 957                           (hwcap & HWCAP_SPECIAL)
 958                           ? __foo_special
 959                           : __foo_default);
 960
 961    This will define the ifunc'ed symbol foo like above.  The redirection of foo
 962    in header file is needed to omit an additional defintion of __GI_foo which
 963    would end in a linker error while linking libc.so.  You have to specify
 964    __redirect_foo as first parameter which is used within libc_ifunc_redirected
 965    macro in conjunction with typeof to define the ifunc'ed symbol foo.
 966
 967    If your function foo has a libc_hidden_proto (foo) defined and calls to foo
 968    within or from outside libc.so should go via ifunc'ed symbol, then you have
 969    to use:
 970
 971    libc_ifunc_hidden (foo, foo,
 972                       (hwcap & HWCAP_SPECIAL)
 973                       ? __foo_special
 974                       : __foo_default);
 975    libc_hidden_def (foo)
 976
 977    The first parameter foo of libc_ifunc_hidden macro is used in the same way
 978    as for libc_ifunc_redirected macro.  */
 979
 980 #define libc_ifunc(name, expr) __ifunc (name, name, expr, void, INIT_ARCH)
 981
 982 #define libc_ifunc_redirected(redirected_name, name, expr)      \
 983   __ifunc (redirected_name, name, expr, void, INIT_ARCH)
 984
 985 #define libc_ifunc_hidden(redirected_name, name, expr)                  \
 986   __ifunc_hidden (redirected_name, name, expr, void, INIT_ARCH)
 987
 988 /* The body of the function is supposed to use __get_cpu_features
 989    which will, if necessary, initialize the data first.  */
 990 #define libm_ifunc_init()
 991 #define libm_ifunc(name, expr)                          \
 992   __ifunc (name, name, expr, void, libm_ifunc_init)
 993
 994 /* Add the compiler optimization to inhibit loop transformation to library
 995    calls.  This is used to avoid recursive calls in memset and memmove
 996    default implementations.  */
 997 #ifdef HAVE_CC_INHIBIT_LOOP_TO_LIBCALL
 998 # define inhibit_loop_to_libcall \
 999     __attribute__ ((__optimize__ ("-fno-tree-loop-distribute-patterns")))
1000 #else
1001 # define inhibit_loop_to_libcall
1002 #endif
1003 \f
1004 /* These macros facilitate sharing source files with gnulib.
1005
1006    They are here instead of sys/cdefs.h because they should not be
1007    used in public header files.
1008
1009    Their definitions should be kept consistent with the definitions in
1010    gnulib-common.m4, but it is not necessary to cater to old non-GCC
1011    compilers, since they will only be used while building glibc itself.
1012    (Note that _GNUC_PREREQ cannot be used in this file.)  */
1013
1014 /* Define as a marker that can be attached to declarations that might not
1015     be used.  This helps to reduce warnings, such as from
1016     GCC -Wunused-parameter.  */
1017 #if __GNUC__ >= 3 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 7)
1018 # define _GL_UNUSED __attribute__ ((__unused__))
1019 #else
1020 # define _GL_UNUSED
1021 #endif
1022
1023 /* gcc supports the "unused" attribute on possibly unused labels, and
1024    g++ has since version 4.5.  Note to support C++ as well as C,
1025    _GL_UNUSED_LABEL should be used with a trailing ;  */
1026 #if !defined __cplusplus || __GNUC__ > 4 \
1027     || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
1028 # define _GL_UNUSED_LABEL _GL_UNUSED
1029 #else
1030 # define _GL_UNUSED_LABEL
1031 #endif
1032
1033 /* The __pure__ attribute was added in gcc 2.96.  */
1034 #if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 96)
1035 # define _GL_ATTRIBUTE_PURE __attribute__ ((__pure__))
1036 #else
1037 # define _GL_ATTRIBUTE_PURE /* empty */
1038 #endif
1039
1040 /* The __const__ attribute was added in gcc 2.95.  */
1041 #if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 95)
1042 # define _GL_ATTRIBUTE_CONST __attribute__ ((__const__))
1043 #else
1044 # define _GL_ATTRIBUTE_CONST /* empty */
1045 #endif
1046
1047 #endif /* !_ISOMAC */
1048 #endif /* libc-symbols.h */