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) 1995-2022 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    <https://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 /* Obtain the definition of symbol_version_reference.  */
  88 #include <libc-symver.h>
  89
  90 /* When PIC is defined and SHARED isn't defined, we are building PIE
  91    by default.  */
  92 #if defined PIC && !defined SHARED
  93 # define BUILD_PIE_DEFAULT 1
  94 #else
  95 # define BUILD_PIE_DEFAULT 0
  96 #endif
  97
  98 /* Define this for the benefit of portable GNU code that wants to check it.
  99    Code that checks with #if will not #include <config.h> again, since we've
 100    already done it (and this file is implicitly included in every compile,
 101    via -include).  Code that checks with #ifdef will #include <config.h>,
 102    but that file should always be idempotent (i.e., it's just #define/#undef
 103    and nothing else anywhere should be changing the macro state it touches),
 104    so it's harmless.  */
 105 #define HAVE_CONFIG_H   0
 106
 107 /* Define these macros for the benefit of portable GNU code that wants to check
 108    them.  Of course, STDC_HEADERS is never false when building libc!  */
 109 #define STDC_HEADERS    1
 110 #define HAVE_MBSTATE_T  1
 111 #define HAVE_MBSRTOWCS  1
 112 #define HAVE_LIBINTL_H  1
 113 #define HAVE_WCTYPE_H   1
 114 #define HAVE_ISWCTYPE   1
 115 #define ENABLE_NLS      1
 116
 117 /* The symbols in all the user (non-_) macros are C symbols.  */
 118
 119 #ifndef __SYMBOL_PREFIX
 120 # define __SYMBOL_PREFIX
 121 #endif
 122
 123 #ifndef C_SYMBOL_NAME
 124 # define C_SYMBOL_NAME(name) name
 125 #endif
 126
 127 #ifndef ASM_LINE_SEP
 128 # define ASM_LINE_SEP ;
 129 #endif
 130
 131 #ifndef __attribute_copy__
 132 /* Provide an empty definition when cdefs.h is not included.  */
 133 # define __attribute_copy__(arg)
 134 #endif
 135
 136 #ifndef __ASSEMBLER__
 137 /* GCC understands weak symbols and aliases; use its interface where
 138    possible, instead of embedded assembly language.  */
 139
 140 /* Define ALIASNAME as a strong alias for NAME.  */
 141 # define strong_alias(name, aliasname) _strong_alias(name, aliasname)
 142 # define _strong_alias(name, aliasname) \
 143   extern __typeof (name) aliasname __attribute__ ((alias (#name))) \
 144     __attribute_copy__ (name);
 145
 146 /* This comes between the return type and function name in
 147    a function definition to make that definition weak.  */
 148 # define weak_function __attribute__ ((weak))
 149 # define weak_const_function __attribute__ ((weak, __const__))
 150
 151 /* Define ALIASNAME as a weak alias for NAME.
 152    If weak aliases are not available, this defines a strong alias.  */
 153 # define weak_alias(name, aliasname) _weak_alias (name, aliasname)
 154 # define _weak_alias(name, aliasname) \
 155   extern __typeof (name) aliasname __attribute__ ((weak, alias (#name))) \
 156     __attribute_copy__ (name);
 157
 158 /* Same as WEAK_ALIAS, but mark symbol as hidden.  */
 159 # define weak_hidden_alias(name, aliasname) \
 160   _weak_hidden_alias (name, aliasname)
 161 # define _weak_hidden_alias(name, aliasname) \
 162   extern __typeof (name) aliasname \
 163     __attribute__ ((weak, alias (#name), __visibility__ ("hidden"))) \
 164     __attribute_copy__ (name);
 165
 166 /* Declare SYMBOL as weak undefined symbol (resolved to 0 if not defined).  */
 167 # define weak_extern(symbol) _weak_extern (weak symbol)
 168 # define _weak_extern(expr) _Pragma (#expr)
 169
 170 /* In shared builds, the expression call_function_static_weak
 171    (FUNCTION-SYMBOL, ARGUMENTS) invokes FUNCTION-SYMBOL (an
 172    identifier) unconditionally, with the (potentially empty) argument
 173    list ARGUMENTS.  In static builds, if FUNCTION-SYMBOL has a
 174    definition, the function is invoked as before; if FUNCTION-SYMBOL
 175    is NULL, no call is performed.  */
 176 # ifdef SHARED
 177 #  define call_function_static_weak(func, ...) func (__VA_ARGS__)
 178 # else  /* !SHARED */
 179 #  define call_function_static_weak(func, ...)          \
 180   ({                                                    \
 181     extern __typeof__ (func) func weak_function;        \
 182     (func != NULL ? func (__VA_ARGS__) : (void)0);      \
 183   })
 184 # endif
 185
 186 #else /* __ASSEMBLER__ */
 187
 188 # ifdef HAVE_ASM_SET_DIRECTIVE
 189 #  define strong_alias(original, alias)                         \
 190   .globl C_SYMBOL_NAME (alias) ASM_LINE_SEP             \
 191   .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original)
 192 #  define strong_data_alias(original, alias) strong_alias(original, alias)
 193 # else
 194 #  define strong_alias(original, alias)                         \
 195   .globl C_SYMBOL_NAME (alias) ASM_LINE_SEP             \
 196   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 197 #  define strong_data_alias(original, alias) strong_alias(original, alias)
 198 # endif
 199
 200 # define weak_alias(original, alias)                                    \
 201   .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP                              \
 202   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 203
 204 # define weak_extern(symbol)                                            \
 205   .weak C_SYMBOL_NAME (symbol)
 206
 207 #endif /* __ASSEMBLER__ */
 208
 209 /* Determine the return address.  */
 210 #define RETURN_ADDRESS(nr) \
 211   __builtin_extract_return_addr (__builtin_return_address (nr))
 212
 213 /* When a reference to SYMBOL is encountered, the linker will emit a
 214    warning message MSG.  */
 215 /* We want the .gnu.warning.SYMBOL section to be unallocated.  */
 216 #define __make_section_unallocated(section_string)      \
 217   asm (".section " section_string "\n\t.previous");
 218
 219 /* Tacking on "\n\t#" to the section name makes gcc put it's bogus
 220    section attributes on what looks like a comment to the assembler.  */
 221 #ifdef HAVE_SECTION_QUOTES
 222 # define __sec_comment "\"\n\t#\""
 223 #else
 224 # define __sec_comment "\n\t#"
 225 #endif
 226 #define link_warning(symbol, msg) \
 227   __make_section_unallocated (".gnu.warning." #symbol) \
 228   static const char __evoke_link_warning_##symbol[]     \
 229     __attribute__ ((used, section (".gnu.warning." #symbol __sec_comment))) \
 230     = msg;
 231
 232 /* A canned warning for sysdeps/stub functions.  */
 233 #define stub_warning(name) \
 234   __make_section_unallocated (".gnu.glibc-stub." #name) \
 235   link_warning (name, #name " is not implemented and will always fail")
 236
 237 /* Warning for linking functions calling dlopen into static binaries.  */
 238 #ifdef SHARED
 239 #define static_link_warning(name)
 240 #else
 241 #define static_link_warning(name) static_link_warning1(name)
 242 #define static_link_warning1(name) \
 243   link_warning(name, "Using '" #name "' in statically linked applications \
 244 requires at runtime the shared libraries from the glibc version used \
 245 for linking")
 246 #endif
 247
 248 /* Resource Freeing Hooks:
 249
 250    Normally a process exits and the OS cleans up any allocated
 251    memory.  However, when tooling like mtrace or valgrind is monitoring
 252    the process we need to free all resources that are part of the
 253    process in order to provide the consistency required to track
 254    memory leaks.
 255
 256    A single public API exists and is __libc_freeres(), and this is used
 257    by applications like valgrind to freee resouces.
 258
 259    There are 3 cases:
 260
 261    (a) __libc_freeres
 262
 263         In this case all you need to do is define the freeing routine:
 264
 265         foo.c:
 266         libfoo_freeres_fn (foo_freeres)
 267         {
 268           complex_free (mem);
 269         }
 270
 271         This ensures the function is called at the right point to free
 272         resources.
 273
 274    (b) __libc_freeres_ptr
 275
 276         The framework for (a) iterates over the list of pointers-to-free
 277         in (b) and frees them.
 278
 279         foo.c:
 280         libc_freeres_ptr (static char *foo_buffer);
 281
 282         Freeing these resources alaways happens last and is equivalent
 283         to registering a function that does 'free (foo_buffer)'.
 284
 285    (c) Explicit lists of free routines to call or objects to free.
 286
 287         It is the intended goal to remove (a) and (b) which have some
 288         non-determinism based on link order, and instead use explicit
 289         lists of functions and frees to resolve cleanup ordering issues
 290         and make it easy to debug and maintain.
 291
 292         As of today the following subsystems use (c):
 293
 294         Per-thread cleanup:
 295         * malloc/thread-freeres.c
 296
 297         libdl cleanup:
 298         * dlfcn/dlfreeres.c
 299
 300         libpthread cleanup:
 301         * nptl/nptlfreeres.c
 302
 303         So if you need any shutdown routines to run you should add them
 304         directly to the appropriate subsystem's shutdown list.  */
 305
 306 /* Resource pointers to free in libc.so.  */
 307 #define libc_freeres_ptr(decl) \
 308   __make_section_unallocated ("__libc_freeres_ptrs, \"aw\", %nobits") \
 309   decl __attribute__ ((section ("__libc_freeres_ptrs" __sec_comment)))
 310
 311 /* Resource freeing functions from libc.so go in this section.  */
 312 #define __libc_freeres_fn_section \
 313   __attribute__ ((__used__, section ("__libc_freeres_fn")))
 314
 315 /* Resource freeing functions for libc.so.  */
 316 #define libc_freeres_fn(name) \
 317   static void name (void) __attribute_used__ __libc_freeres_fn_section; \
 318   text_set_element (__libc_subfreeres, name);                           \
 319   static void name (void)
 320
 321 /* Declare SYMBOL to be TYPE (`function' or `object') of SIZE bytes
 322    alias to ORIGINAL, when the assembler supports such declarations
 323    (such as in ELF).
 324    This is only necessary when defining something in assembly, or playing
 325    funny alias games where the size should be other than what the compiler
 326    thinks it is.  */
 327 #ifdef __ASSEMBLER__
 328 # define declare_object_symbol_alias(symbol, original, size) \
 329   declare_object_symbol_alias_1 (symbol, original, size)
 330 # define declare_object_symbol_alias_1(symbol, original, s_size) \
 331    strong_alias (original, symbol) ASM_LINE_SEP \
 332    .type C_SYMBOL_NAME (symbol), %object ASM_LINE_SEP \
 333    .size C_SYMBOL_NAME (symbol), s_size ASM_LINE_SEP
 334 #else /* Not __ASSEMBLER__.  */
 335 # define declare_symbol_alias(symbol, original, type, size) \
 336   declare_symbol_alias_1 (symbol, original, type, size)
 337 # define declare_symbol_alias_1(symbol, original, type, size) \
 338    asm (".globl " __SYMBOL_PREFIX #symbol \
 339         "\n\t" declare_symbol_alias_1_alias (symbol, original) \
 340         "\n\t.type " __SYMBOL_PREFIX #symbol ", " \
 341         "%" #type \
 342         "\n\t.size " __SYMBOL_PREFIX #symbol ", " #size);
 343 # ifdef HAVE_ASM_SET_DIRECTIVE
 344 #  define declare_symbol_alias_1_alias(symbol, original) \
 345      ".set " __SYMBOL_PREFIX #symbol ", " __SYMBOL_PREFIX #original
 346 # else
 347 #  define declare_symbol_alias_1_alias(symbol, original) \
 348      __SYMBOL_PREFIX #symbol " = " __SYMBOL_PREFIX #original
 349 # endif /* HAVE_ASM_SET_DIRECTIVE */
 350 #endif /* __ASSEMBLER__ */
 351
 352
 353 /*
 354 \f
 355 */
 356
 357 #ifdef HAVE_GNU_RETAIN
 358 # define attribute_used_retain __attribute__ ((__used__, __retain__))
 359 #else
 360 # define attribute_used_retain __attribute__ ((__used__))
 361 #endif
 362
 363 /* Symbol set support macros.  */
 364
 365 /* Make SYMBOL, which is in the text segment, an element of SET.  */
 366 #define text_set_element(set, symbol)   _elf_set_element(set, symbol)
 367 /* Make SYMBOL, which is in the data segment, an element of SET.  */
 368 #define data_set_element(set, symbol)   _elf_set_element(set, symbol)
 369 /* Make SYMBOL, which is in the bss segment, an element of SET.  */
 370 #define bss_set_element(set, symbol)    _elf_set_element(set, symbol)
 371
 372 /* These are all done the same way in ELF.
 373    There is a new section created for each set.  */
 374 #ifdef SHARED
 375 /* When building a shared library, make the set section writable,
 376    because it will need to be relocated at run time anyway.  */
 377 # define _elf_set_element(set, symbol) \
 378     static const void *__elf_set_##set##_element_##symbol##__ \
 379       attribute_used_retain __attribute__ ((section (#set))) = &(symbol)
 380 #else
 381 # define _elf_set_element(set, symbol) \
 382     static const void *const __elf_set_##set##_element_##symbol##__ \
 383       attribute_used_retain __attribute__ ((section (#set))) = &(symbol)
 384 #endif
 385
 386 /* Define SET as a symbol set.  This may be required (it is in a.out) to
 387    be able to use the set's contents.  */
 388 #define symbol_set_define(set)  symbol_set_declare(set)
 389
 390 /* Declare SET for use in this module, if defined in another module.
 391    In a shared library, this is always local to that shared object.
 392    For static linking, the set might be wholly absent and so we use
 393    weak references.  */
 394 #define symbol_set_declare(set) \
 395   extern char const __start_##set[] __symbol_set_attribute; \
 396   extern char const __stop_##set[] __symbol_set_attribute;
 397 #ifdef SHARED
 398 # define __symbol_set_attribute attribute_hidden
 399 #else
 400 # define __symbol_set_attribute __attribute__ ((weak))
 401 #endif
 402
 403 /* Return a pointer (void *const *) to the first element of SET.  */
 404 #define symbol_set_first_element(set)   ((void *const *) (&__start_##set))
 405
 406 /* Return true iff PTR (a void *const *) has been incremented
 407    past the last element in SET.  */
 408 #define symbol_set_end_p(set, ptr) ((ptr) >= (void *const *) &__stop_##set)
 409
 410 #ifdef SHARED
 411 # define symbol_version(real, name, version) \
 412   symbol_version_reference(real, name, version)
 413 # define default_symbol_version(real, name, version) \
 414      _default_symbol_version(real, name, version)
 415 /* See <libc-symver.h>.  */
 416 # ifdef __ASSEMBLER__
 417 #  define _default_symbol_version(real, name, version) \
 418   _set_symbol_version (real, name@@version)
 419 # else
 420 #  define _default_symbol_version(real, name, version) \
 421   _set_symbol_version (real, #name "@@" #version)
 422 # endif
 423
 424 /* Evalutes to a string literal for VERSION in LIB.  */
 425 # define symbol_version_string(lib, version) \
 426   _symbol_version_stringify_1 (VERSION_##lib##_##version)
 427 # define _symbol_version_stringify_1(arg) _symbol_version_stringify_2 (arg)
 428 # define _symbol_version_stringify_2(arg) #arg
 429
 430 #else /* !SHARED */
 431 # define symbol_version(real, name, version)
 432 # define default_symbol_version(real, name, version) \
 433   strong_alias(real, name)
 434 #endif
 435
 436 #if defined SHARED || defined LIBC_NONSHARED \
 437   || (BUILD_PIE_DEFAULT && IS_IN (libc))
 438 # define attribute_hidden __attribute__ ((visibility ("hidden")))
 439 #else
 440 # define attribute_hidden
 441 #endif
 442
 443 #define attribute_tls_model_ie __attribute__ ((tls_model ("initial-exec")))
 444
 445 #define attribute_relro __attribute__ ((section (".data.rel.ro")))
 446
 447
 448 /* Used to disable stack protection in sensitive places, like ifunc
 449    resolvers and early static TLS init.  */
 450 #ifdef HAVE_CC_NO_STACK_PROTECTOR
 451 # define inhibit_stack_protector \
 452     __attribute__ ((__optimize__ ("-fno-stack-protector")))
 453 #else
 454 # define inhibit_stack_protector
 455 #endif
 456
 457 /* The following macros are used for PLT bypassing within libc.so
 458    (and if needed other libraries similarly).
 459    First of all, you need to have the function prototyped somewhere,
 460    say in foo/foo.h:
 461
 462    int foo (int __bar);
 463
 464    If calls to foo within libc.so should always go to foo defined in libc.so,
 465    then in include/foo.h you add:
 466
 467    libc_hidden_proto (foo)
 468
 469    line and after the foo function definition:
 470
 471    int foo (int __bar)
 472    {
 473      return __bar;
 474    }
 475    libc_hidden_def (foo)
 476
 477    or
 478
 479    int foo (int __bar)
 480    {
 481      return __bar;
 482    }
 483    libc_hidden_weak (foo)
 484
 485    Similarly for global data.  If references to foo within libc.so should
 486    always go to foo defined in libc.so, then in include/foo.h you add:
 487
 488    libc_hidden_proto (foo)
 489
 490    line and after foo's definition:
 491
 492    int foo = INITIAL_FOO_VALUE;
 493    libc_hidden_data_def (foo)
 494
 495    or
 496
 497    int foo = INITIAL_FOO_VALUE;
 498    libc_hidden_data_weak (foo)
 499
 500    If foo is normally just an alias (strong or weak) to some other function,
 501    you should use the normal strong_alias first, then add libc_hidden_def
 502    or libc_hidden_weak:
 503
 504    int baz (int __bar)
 505    {
 506      return __bar;
 507    }
 508    strong_alias (baz, foo)
 509    libc_hidden_weak (foo)
 510
 511    If the function should be internal to multiple objects, say ld.so and
 512    libc.so, the best way is to use:
 513
 514    #if IS_IN (libc) || IS_IN (rtld)
 515    hidden_proto (foo)
 516    #endif
 517
 518    in include/foo.h and the normal macros at all function definitions
 519    depending on what DSO they belong to.
 520
 521    If versioned_symbol macro is used to define foo,
 522    libc_hidden_ver macro should be used, as in:
 523
 524    int __real_foo (int __bar)
 525    {
 526      return __bar;
 527    }
 528    versioned_symbol (libc, __real_foo, foo, GLIBC_2_1);
 529    libc_hidden_ver (__real_foo, foo)  */
 530
 531 #if defined SHARED && !defined NO_HIDDEN
 532 # ifndef __ASSEMBLER__
 533 #  define __hidden_proto_hiddenattr(attrs...) \
 534   __attribute__ ((visibility ("hidden"), ##attrs))
 535 #  define hidden_proto(name, attrs...) \
 536   __hidden_proto (name, , __GI_##name, ##attrs)
 537 #  define hidden_tls_proto(name, attrs...) \
 538   __hidden_proto (name, __thread, __GI_##name, ##attrs)
 539 #  define __hidden_proto(name, thread, internal, attrs...)           \
 540   extern thread __typeof (name) name __asm__ (__hidden_asmname (#internal)) \
 541   __hidden_proto_hiddenattr (attrs);
 542 #  define __hidden_asmname(name) \
 543   __hidden_asmname1 (__USER_LABEL_PREFIX__, name)
 544 #  define __hidden_asmname1(prefix, name) __hidden_asmname2(prefix, name)
 545 #  define __hidden_asmname2(prefix, name) #prefix name
 546 #  define __hidden_ver1(local, internal, name) \
 547   __hidden_ver2 (, local, internal, name)
 548 #  define __hidden_ver2(thread, local, internal, name)                  \
 549   extern thread __typeof (name) __EI_##name \
 550     __asm__(__hidden_asmname (#internal));  \
 551   extern thread __typeof (name) __EI_##name \
 552     __attribute__((alias (__hidden_asmname (#local))))  \
 553     __attribute_copy__ (name)
 554 #  define hidden_ver(local, name)       __hidden_ver1(local, __GI_##name, name);
 555 #  define hidden_data_ver(local, name)  hidden_ver(local, name)
 556 #  define hidden_def(name)              __hidden_ver1(__GI_##name, name, name);
 557 #  define hidden_data_def(name)         hidden_def(name)
 558 #  define hidden_tls_def(name)                          \
 559   __hidden_ver2 (__thread, __GI_##name, name, name);
 560 #  define hidden_weak(name) \
 561         __hidden_ver1(__GI_##name, name, name) __attribute__((weak));
 562 #  define hidden_data_weak(name)        hidden_weak(name)
 563 #  define hidden_nolink(name, lib, version) \
 564   __hidden_nolink1 (__GI_##name, __EI_##name, name, VERSION_##lib##_##version)
 565 #  define __hidden_nolink1(local, internal, name, version) \
 566   __hidden_nolink2 (local, internal, name, version)
 567 #  define __hidden_nolink2(local, internal, name, version) \
 568   extern __typeof (name) internal __attribute__ ((alias (#local)))      \
 569     __attribute_copy__ (name);                                          \
 570   __hidden_nolink3 (local, internal, #name "@" #version)
 571 #  define __hidden_nolink3(local, internal, vername) \
 572   __asm__ (".symver " #internal ", " vername);
 573 # else
 574 /* For assembly, we need to do the opposite of what we do in C:
 575    in assembly gcc __REDIRECT stuff is not in place, so functions
 576    are defined by its normal name and we need to create the
 577    __GI_* alias to it, in C __REDIRECT causes the function definition
 578    to use __GI_* name and we need to add alias to the real name.
 579    There is no reason to use hidden_weak over hidden_def in assembly,
 580    but we provide it for consistency with the C usage.
 581    hidden_proto doesn't make sense for assembly but the equivalent
 582    is to call via the HIDDEN_JUMPTARGET macro instead of JUMPTARGET.  */
 583 #  define hidden_def(name)      strong_alias (name, __GI_##name)
 584 #  define hidden_weak(name)     hidden_def (name)
 585 #  define hidden_ver(local, name) strong_alias (local, __GI_##name)
 586 #  define hidden_data_def(name) strong_data_alias (name, __GI_##name)
 587 #  define hidden_tls_def(name)  hidden_data_def (name)
 588 #  define hidden_data_weak(name)        hidden_data_def (name)
 589 #  define hidden_data_ver(local, name) strong_data_alias (local, __GI_##name)
 590 #  define HIDDEN_JUMPTARGET(name) __GI_##name
 591 # endif
 592 #else
 593 # ifndef __ASSEMBLER__
 594 #  if !defined SHARED && IS_IN (libc) && !defined LIBC_NONSHARED \
 595       && (!defined PIC || !defined NO_HIDDEN_EXTERN_FUNC_IN_PIE) \
 596       && !defined NO_HIDDEN
 597 #   define __hidden_proto_hiddenattr(attrs...) \
 598   __attribute__ ((visibility ("hidden"), ##attrs))
 599 #   define hidden_proto(name, attrs...) \
 600   __hidden_proto (name, , name, ##attrs)
 601 #   define hidden_tls_proto(name, attrs...) \
 602   __hidden_proto (name, __thread, name, ##attrs)
 603 #  define __hidden_proto(name, thread, internal, attrs...)           \
 604   extern thread __typeof (name) name __hidden_proto_hiddenattr (attrs);
 605 # else
 606 #   define hidden_proto(name, attrs...)
 607 #   define hidden_tls_proto(name, attrs...)
 608 # endif
 609 # else
 610 #  define HIDDEN_JUMPTARGET(name) JUMPTARGET(name)
 611 # endif /* Not  __ASSEMBLER__ */
 612 # define hidden_weak(name)
 613 # define hidden_def(name)
 614 # define hidden_ver(local, name)
 615 # define hidden_data_weak(name)
 616 # define hidden_data_def(name)
 617 # define hidden_tls_def(name)
 618 # define hidden_data_ver(local, name)
 619 # define hidden_nolink(name, lib, version)
 620 #endif
 621
 622 #if IS_IN (libc)
 623 # define libc_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 624 # define libc_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
 625 # define libc_hidden_def(name) hidden_def (name)
 626 # define libc_hidden_weak(name) hidden_weak (name)
 627 # define libc_hidden_nolink_sunrpc(name, version) hidden_nolink (name, libc, version)
 628 # define libc_hidden_ver(local, name) hidden_ver (local, name)
 629 # define libc_hidden_data_def(name) hidden_data_def (name)
 630 # define libc_hidden_tls_def(name) hidden_tls_def (name)
 631 # define libc_hidden_data_weak(name) hidden_data_weak (name)
 632 # define libc_hidden_data_ver(local, name) hidden_data_ver (local, name)
 633 #else
 634 # define libc_hidden_proto(name, attrs...)
 635 # define libc_hidden_tls_proto(name, attrs...)
 636 # define libc_hidden_def(name)
 637 # define libc_hidden_weak(name)
 638 # define libc_hidden_ver(local, name)
 639 # define libc_hidden_data_def(name)
 640 # define libc_hidden_tls_def(name)
 641 # define libc_hidden_data_weak(name)
 642 # define libc_hidden_data_ver(local, name)
 643 #endif
 644
 645 #if IS_IN (rtld)
 646 # define rtld_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 647 # define rtld_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
 648 # define rtld_hidden_def(name) hidden_def (name)
 649 # define rtld_hidden_weak(name) hidden_weak (name)
 650 # define rtld_hidden_ver(local, name) hidden_ver (local, name)
 651 # define rtld_hidden_data_def(name) hidden_data_def (name)
 652 # define rtld_hidden_tls_def(name) hidden_tls_def (name)
 653 # define rtld_hidden_data_weak(name) hidden_data_weak (name)
 654 # define rtld_hidden_data_ver(local, name) hidden_data_ver (local, name)
 655 #else
 656 # define rtld_hidden_proto(name, attrs...)
 657 # define rtld_hidden_tls_proto(name, attrs...)
 658 # define rtld_hidden_def(name)
 659 # define rtld_hidden_weak(name)
 660 # define rtld_hidden_ver(local, name)
 661 # define rtld_hidden_data_def(name)
 662 # define rtld_hidden_tls_def(name)
 663 # define rtld_hidden_data_weak(name)
 664 # define rtld_hidden_data_ver(local, name)
 665 #endif
 666
 667 #if IS_IN (libm)
 668 # define libm_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 669 # define libm_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
 670 # define libm_hidden_def(name) hidden_def (name)
 671 # define libm_hidden_weak(name) hidden_weak (name)
 672 # define libm_hidden_ver(local, name) hidden_ver (local, name)
 673 # define libm_hidden_data_def(name) hidden_data_def (name)
 674 # define libm_hidden_tls_def(name) hidden_tls_def (name)
 675 # define libm_hidden_data_weak(name) hidden_data_weak (name)
 676 # define libm_hidden_data_ver(local, name) hidden_data_ver (local, name)
 677 #else
 678 # define libm_hidden_proto(name, attrs...)
 679 # define libm_hidden_tls_proto(name, attrs...)
 680 # define libm_hidden_def(name)
 681 # define libm_hidden_weak(name)
 682 # define libm_hidden_ver(local, name)
 683 # define libm_hidden_data_def(name)
 684 # define libm_hidden_tls_def(name)
 685 # define libm_hidden_data_weak(name)
 686 # define libm_hidden_data_ver(local, name)
 687 #endif
 688
 689 #if IS_IN (libmvec)
 690 # define libmvec_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 691 # define libmvec_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
 692 # define libmvec_hidden_def(name) hidden_def (name)
 693 # define libmvec_hidden_weak(name) hidden_weak (name)
 694 # define libmvec_hidden_ver(local, name) hidden_ver (local, name)
 695 # define libmvec_hidden_data_def(name) hidden_data_def (name)
 696 # define libmvec_hidden_tls_def(name) hidden_tls_def (name)
 697 # define libmvec_hidden_data_weak(name) hidden_data_weak (name)
 698 # define libmvec_hidden_data_ver(local, name) hidden_data_ver (local, name)
 699 #else
 700 # define libmvec_hidden_proto(name, attrs...)
 701 # define libmvec_hidden_tls_proto(name, attrs...)
 702 # define libmvec_hidden_def(name)
 703 # define libmvec_hidden_weak(name)
 704 # define libmvec_hidden_ver(local, name)
 705 # define libmvec_hidden_data_def(name)
 706 # define libmvec_hidden_tls_def(name)
 707 # define libmvec_hidden_data_weak(name)
 708 # define libmvec_hidden_data_ver(local, name)
 709 #endif
 710
 711 #if IS_IN (libresolv)
 712 # define libresolv_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 713 # define libresolv_hidden_tls_proto(name, attrs...) \
 714   hidden_tls_proto (name, ##attrs)
 715 # define libresolv_hidden_def(name) hidden_def (name)
 716 # define libresolv_hidden_weak(name) hidden_weak (name)
 717 # define libresolv_hidden_ver(local, name) hidden_ver (local, name)
 718 # define libresolv_hidden_data_def(name) hidden_data_def (name)
 719 # define libresolv_hidden_tls_def(name) hidden_tls_def (name)
 720 # define libresolv_hidden_data_weak(name) hidden_data_weak (name)
 721 # define libresolv_hidden_data_ver(local, name) hidden_data_ver (local, name)
 722 #else
 723 # define libresolv_hidden_proto(name, attrs...)
 724 # define libresolv_hidden_tls_proto(name, attrs...)
 725 # define libresolv_hidden_def(name)
 726 # define libresolv_hidden_weak(name)
 727 # define libresolv_hidden_ver(local, name)
 728 # define libresolv_hidden_data_def(name)
 729 # define libresolv_hidden_tls_def(name)
 730 # define libresolv_hidden_data_weak(name)
 731 # define libresolv_hidden_data_ver(local, name)
 732 #endif
 733
 734 #if IS_IN (libpthread)
 735 # define libpthread_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 736 # define libpthread_hidden_tls_proto(name, attrs...) \
 737   hidden_tls_proto (name, ##attrs)
 738 # define libpthread_hidden_def(name) hidden_def (name)
 739 # define libpthread_hidden_weak(name) hidden_weak (name)
 740 # define libpthread_hidden_ver(local, name) hidden_ver (local, name)
 741 # define libpthread_hidden_data_def(name) hidden_data_def (name)
 742 # define libpthread_hidden_tls_def(name) hidden_tls_def (name)
 743 # define libpthread_hidden_data_weak(name) hidden_data_weak (name)
 744 # define libpthread_hidden_data_ver(local, name) hidden_data_ver (local, name)
 745 #else
 746 # define libpthread_hidden_proto(name, attrs...)
 747 # define libpthread_hidden_tls_proto(name, attrs...)
 748 # define libpthread_hidden_def(name)
 749 # define libpthread_hidden_weak(name)
 750 # define libpthread_hidden_ver(local, name)
 751 # define libpthread_hidden_data_def(name)
 752 # define libpthread_hidden_tls_def(name)
 753 # define libpthread_hidden_data_weak(name)
 754 # define libpthread_hidden_data_ver(local, name)
 755 #endif
 756
 757 #if IS_IN (librt)
 758 # define librt_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 759 # define librt_hidden_tls_proto(name, attrs...) \
 760   hidden_tls_proto (name, ##attrs)
 761 # define librt_hidden_def(name) hidden_def (name)
 762 # define librt_hidden_weak(name) hidden_weak (name)
 763 # define librt_hidden_ver(local, name) hidden_ver (local, name)
 764 # define librt_hidden_data_def(name) hidden_data_def (name)
 765 # define librt_hidden_tls_def(name) hidden_tls_def (name)
 766 # define librt_hidden_data_weak(name) hidden_data_weak (name)
 767 # define librt_hidden_data_ver(local, name) hidden_data_ver (local, name)
 768 #else
 769 # define librt_hidden_proto(name, attrs...)
 770 # define librt_hidden_tls_proto(name, attrs...)
 771 # define librt_hidden_def(name)
 772 # define librt_hidden_weak(name)
 773 # define librt_hidden_ver(local, name)
 774 # define librt_hidden_data_def(name)
 775 # define librt_hidden_tls_def(name)
 776 # define librt_hidden_data_weak(name)
 777 # define librt_hidden_data_ver(local, name)
 778 #endif
 779
 780 #if IS_IN (libdl)
 781 # define libdl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 782 # define libdl_hidden_tls_proto(name, attrs...) \
 783   hidden_tls_proto (name, ##attrs)
 784 # define libdl_hidden_def(name) hidden_def (name)
 785 # define libdl_hidden_weak(name) hidden_weak (name)
 786 # define libdl_hidden_ver(local, name) hidden_ver (local, name)
 787 # define libdl_hidden_data_def(name) hidden_data_def (name)
 788 # define libdl_hidden_tls_def(name) hidden_tls_def (name)
 789 # define libdl_hidden_data_weak(name) hidden_data_weak (name)
 790 # define libdl_hidden_data_ver(local, name) hidden_data_ver (local, name)
 791 #else
 792 # define libdl_hidden_proto(name, attrs...)
 793 # define libdl_hidden_tls_proto(name, attrs...)
 794 # define libdl_hidden_def(name)
 795 # define libdl_hidden_weak(name)
 796 # define libdl_hidden_ver(local, name)
 797 # define libdl_hidden_data_def(name)
 798 # define libdl_hidden_tls_def(name)
 799 # define libdl_hidden_data_weak(name)
 800 # define libdl_hidden_data_ver(local, name)
 801 #endif
 802
 803 #if IS_IN (libnsl)
 804 # define libnsl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 805 # define libnsl_hidden_tls_proto(name, attrs...) \
 806   hidden_tls_proto (name, ##attrs)
 807 # define libnsl_hidden_nolink_def(name, version) hidden_nolink (name, libnsl, version)
 808 # define libnsl_hidden_weak(name) hidden_weak (name)
 809 # define libnsl_hidden_ver(local, name) hidden_ver (local, name)
 810 # define libnsl_hidden_data_def(name) hidden_data_def (name)
 811 # define libnsl_hidden_tls_def(name) hidden_tls_def (name)
 812 # define libnsl_hidden_data_weak(name) hidden_data_weak (name)
 813 # define libnsl_hidden_data_ver(local, name) hidden_data_ver (local, name)
 814 #else
 815 # define libnsl_hidden_proto(name, attrs...)
 816 # define libnsl_hidden_tls_proto(name, attrs...)
 817 # define libnsl_hidden_weak(name)
 818 # define libnsl_hidden_ver(local, name)
 819 # define libnsl_hidden_data_def(name)
 820 # define libnsl_hidden_tls_def(name)
 821 # define libnsl_hidden_data_weak(name)
 822 # define libnsl_hidden_data_ver(local, name)
 823 #endif
 824
 825 #define libc_hidden_builtin_proto(name, attrs...) libc_hidden_proto (name, ##attrs)
 826 #define libc_hidden_builtin_def(name) libc_hidden_def (name)
 827 #define libc_hidden_builtin_weak(name) libc_hidden_weak (name)
 828 #define libc_hidden_builtin_ver(local, name) libc_hidden_ver (local, name)
 829
 830 #define libc_hidden_ldbl_proto(name, attrs...) libc_hidden_proto (name, ##attrs)
 831 #ifdef __ASSEMBLER__
 832 # define HIDDEN_BUILTIN_JUMPTARGET(name) HIDDEN_JUMPTARGET(name)
 833 #endif
 834
 835 #if IS_IN (libutil)
 836 # define libutil_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 837 # define libutil_hidden_tls_proto(name, attrs...) \
 838   hidden_tls_proto (name, ##attrs)
 839 # define libutil_hidden_def(name) hidden_def (name)
 840 # define libutil_hidden_weak(name) hidden_weak (name)
 841 # define libutil_hidden_ver(local, name) hidden_ver (local, name)
 842 # define libutil_hidden_data_def(name) hidden_data_def (name)
 843 # define libutil_hidden_tls_def(name) hidden_tls_def (name)
 844 # define libutil_hidden_data_weak(name) hidden_data_weak (name)
 845 # define libutil_hidden_data_ver(local, name) hidden_data_ver (local, name)
 846 #else
 847 # define libutil_hidden_proto(name, attrs...)
 848 # define libutil_hidden_tls_proto(name, attrs...)
 849 # define libutil_hidden_def(name)
 850 # define libutil_hidden_weak(name)
 851 # define libutil_hidden_ver(local, name)
 852 # define libutil_hidden_data_def(name)
 853 # define libutil_hidden_tls_def(name)
 854 # define libutil_hidden_data_weak(name)
 855 # define libutil_hidden_data_ver(local, name)
 856 #endif
 857
 858 #if IS_IN (libanl)
 859 # define libanl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 860 # define libanl_hidden_def(name) hidden_def (name)
 861 #else
 862 # define libanl_hidden_proto(name, attrs...)
 863 # define libanl_hidden_def(name)
 864 #endif
 865
 866 /* Get some dirty hacks.  */
 867 #include <symbol-hacks.h>
 868
 869 /* Move compatibility symbols out of the way by placing them all in a
 870    special section.  */
 871 #ifndef __ASSEMBLER__
 872 # define attribute_compat_text_section \
 873     __attribute__ ((section (".text.compat")))
 874 # define attribute_compat_data_section \
 875     __attribute__ ((section (".data.compat")))
 876 #else
 877 # define compat_text_section .section ".text.compat", "ax";
 878 # define compat_data_section .section ".data.compat", "aw";
 879 #endif
 880
 881 /* Helper / base  macros for indirect function symbols.  */
 882 #define __ifunc_resolver(type_name, name, expr, arg, init, classifier)  \
 883   classifier inhibit_stack_protector                                    \
 884   __typeof (type_name) *name##_ifunc (arg)                              \
 885   {                                                                     \
 886     init ();                                                            \
 887     __typeof (type_name) *res = expr;                                   \
 888     return res;                                                         \
 889   }
 890
 891 #ifdef HAVE_GCC_IFUNC
 892 # define __ifunc(type_name, name, expr, arg, init)                      \
 893   extern __typeof (type_name) name __attribute__                        \
 894                               ((ifunc (#name "_ifunc")));               \
 895   __ifunc_resolver (type_name, name, expr, arg, init, static)
 896
 897 # define __ifunc_hidden(type_name, name, expr, arg, init)       \
 898   __ifunc (type_name, name, expr, arg, init)
 899 #else
 900 /* Gcc does not support __attribute__ ((ifunc (...))).  Use the old behaviour
 901    as fallback.  But keep in mind that the debug information for the ifunc
 902    resolver functions is not correct.  It contains the ifunc'ed function as
 903    DW_AT_linkage_name.  E.g. lldb uses this field and an inferior function
 904    call of the ifunc'ed function will fail due to "no matching function for
 905    call to ..." because the ifunc'ed function and the resolver function have
 906    different signatures.  (Gcc support is disabled at least on a ppc64le
 907    Ubuntu 14.04 system.)  */
 908
 909 # define __ifunc(type_name, name, expr, arg, init)                      \
 910   extern __typeof (type_name) name;                                     \
 911   __typeof (type_name) *name##_ifunc (arg) __asm__ (#name);             \
 912   __ifunc_resolver (type_name, name, expr, arg, init,)                  \
 913  __asm__ (".type " #name ", %gnu_indirect_function");
 914
 915 # define __ifunc_hidden(type_name, name, expr, arg, init)               \
 916   extern __typeof (type_name) __libc_##name;                            \
 917   __ifunc (type_name, __libc_##name, expr, arg, init)                   \
 918   strong_alias (__libc_##name, name);
 919 #endif /* !HAVE_GCC_IFUNC  */
 920
 921 /* The following macros are used for indirect function symbols in libc.so.
 922    First of all, you need to have the function prototyped somewhere,
 923    say in foo.h:
 924
 925    int foo (int __bar);
 926
 927    If you have an implementation for foo which e.g. uses a special hardware
 928    feature which isn't available on all machines where this libc.so will be
 929    used but decideable if available at runtime e.g. via hwcaps, you can provide
 930    two or multiple implementations of foo:
 931
 932    int __foo_default (int __bar)
 933    {
 934      return __bar;
 935    }
 936
 937    int __foo_special (int __bar)
 938    {
 939      return __bar;
 940    }
 941
 942    If your function foo has no libc_hidden_proto (foo) defined for PLT
 943    bypassing, you can use:
 944
 945    #define INIT_ARCH() unsigned long int hwcap = __GLRO(dl_hwcap);
 946
 947    libc_ifunc (foo, (hwcap & HWCAP_SPECIAL) ? __foo_special : __foo_default);
 948
 949    This will define a resolver function for foo which returns __foo_special or
 950    __foo_default depending on your specified expression.  Please note that you
 951    have to define a macro function INIT_ARCH before using libc_ifunc macro as
 952    it is called by the resolver function before evaluating the specified
 953    expression.  In this example it is used to prepare the hwcap variable.
 954    The resolver function is assigned to an ifunc'ed symbol foo.  Calls to foo
 955    from inside or outside of libc.so will be indirected by a PLT call.
 956
 957    If your function foo has a libc_hidden_proto (foo) defined for PLT bypassing
 958    and calls to foo within libc.so should always go to one specific
 959    implementation of foo e.g. __foo_default then you have to add:
 960
 961    __hidden_ver1 (__foo_default, __GI_foo, __foo_default);
 962
 963    or a tweaked definition of libc_hidden_def macro after the __foo_default
 964    function definition.  Calls to foo within libc.so will always go directly to
 965    __foo_default.  Calls to foo from outside libc.so will be indirected by a
 966    PLT call to ifunc'ed symbol foo which you have to define in a separate
 967    compile unit:
 968
 969    #define foo __redirect_foo
 970    #include <foo.h>
 971    #undef foo
 972
 973    extern __typeof (__redirect_foo) __foo_default attribute_hidden;
 974    extern __typeof (__redirect_foo) __foo_special attribute_hidden;
 975
 976    libc_ifunc_redirected (__redirect_foo, foo,
 977                           (hwcap & HWCAP_SPECIAL)
 978                           ? __foo_special
 979                           : __foo_default);
 980
 981    This will define the ifunc'ed symbol foo like above.  The redirection of foo
 982    in header file is needed to omit an additional defintion of __GI_foo which
 983    would end in a linker error while linking libc.so.  You have to specify
 984    __redirect_foo as first parameter which is used within libc_ifunc_redirected
 985    macro in conjunction with typeof to define the ifunc'ed symbol foo.
 986
 987    If your function foo has a libc_hidden_proto (foo) defined and calls to foo
 988    within or from outside libc.so should go via ifunc'ed symbol, then you have
 989    to use:
 990
 991    libc_ifunc_hidden (foo, foo,
 992                       (hwcap & HWCAP_SPECIAL)
 993                       ? __foo_special
 994                       : __foo_default);
 995    libc_hidden_def (foo)
 996
 997    The first parameter foo of libc_ifunc_hidden macro is used in the same way
 998    as for libc_ifunc_redirected macro.  */
 999
1000 #define libc_ifunc(name, expr) __ifunc (name, name, expr, void, INIT_ARCH)
1001
1002 #define libc_ifunc_redirected(redirected_name, name, expr)      \
1003   __ifunc (redirected_name, name, expr, void, INIT_ARCH)
1004
1005 #define libc_ifunc_hidden(redirected_name, name, expr)                  \
1006   __ifunc_hidden (redirected_name, name, expr, void, INIT_ARCH)
1007
1008 /* The body of the function is supposed to use __get_cpu_features
1009    which will, if necessary, initialize the data first.  */
1010 #define libm_ifunc_init()
1011 #define libm_ifunc(name, expr)                          \
1012   __ifunc (name, name, expr, void, libm_ifunc_init)
1013
1014 /* Add the compiler optimization to inhibit loop transformation to library
1015    calls.  This is used to avoid recursive calls in memset and memmove
1016    default implementations.  */
1017 #ifdef HAVE_CC_INHIBIT_LOOP_TO_LIBCALL
1018 # define inhibit_loop_to_libcall \
1019     __attribute__ ((__optimize__ ("-fno-tree-loop-distribute-patterns")))
1020 #else
1021 # define inhibit_loop_to_libcall
1022 #endif
1023 \f
1024 /* These macros facilitate sharing source files with gnulib.
1025
1026    They are here instead of sys/cdefs.h because they should not be
1027    used in public header files.
1028
1029    Their definitions should be kept consistent with the definitions in
1030    gnulib-common.m4, but it is not necessary to cater to old non-GCC
1031    compilers, since they will only be used while building glibc itself.
1032    (Note that _GNUC_PREREQ cannot be used in this file.)  */
1033
1034 /* Define as a marker that can be attached to declarations that might not
1035     be used.  This helps to reduce warnings, such as from
1036     GCC -Wunused-parameter.  */
1037 #if __GNUC__ >= 3 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 7)
1038 # define _GL_UNUSED __attribute__ ((__unused__))
1039 #else
1040 # define _GL_UNUSED
1041 #endif
1042
1043 /* gcc supports the "unused" attribute on possibly unused labels, and
1044    g++ has since version 4.5.  Note to support C++ as well as C,
1045    _GL_UNUSED_LABEL should be used with a trailing ;  */
1046 #if !defined __cplusplus || __GNUC__ > 4 \
1047     || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
1048 # define _GL_UNUSED_LABEL _GL_UNUSED
1049 #else
1050 # define _GL_UNUSED_LABEL
1051 #endif
1052
1053 /* The __pure__ attribute was added in gcc 2.96.  */
1054 #if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 96)
1055 # define _GL_ATTRIBUTE_PURE __attribute__ ((__pure__))
1056 #else
1057 # define _GL_ATTRIBUTE_PURE /* empty */
1058 #endif
1059
1060 /* The __const__ attribute was added in gcc 2.95.  */
1061 #if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 95)
1062 # define _GL_ATTRIBUTE_CONST __attribute__ ((__const__))
1063 #else
1064 # define _GL_ATTRIBUTE_CONST /* empty */
1065 #endif
1066
1067 #endif /* !_ISOMAC */
1068 #endif /* libc-symbols.h */