lib/stddef.in.h

   1 /* A substitute for POSIX 2008 <stddef.h>, for platforms that have issues.
   2
   3    Copyright (C) 2009-2024 Free Software Foundation, Inc.
   4
   5    This file is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    License, or (at your option) any later version.
   9
  10    This file is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Eric Blake.  */
  19
  20 /*
  21  * POSIX 2008 and ISO C 23 <stddef.h> for platforms that have issues.
  22  * <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/stddef.h.html>
  23  */
  24
  25 #if __GNUC__ >= 3
  26 @PRAGMA_SYSTEM_HEADER@
  27 #endif
  28 @PRAGMA_COLUMNS@
  29
  30 #if defined __need_wchar_t || defined __need_size_t  \
  31   || defined __need_ptrdiff_t || defined __need_NULL \
  32   || defined __need_wint_t
  33 /* Special invocation convention inside gcc header files.  In
  34    particular, gcc provides a version of <stddef.h> that blindly
  35    redefines NULL even when __need_wint_t was defined, even though
  36    wint_t is not normally provided by <stddef.h>.  Hence, we must
  37    remember if special invocation has ever been used to obtain wint_t,
  38    in which case we need to clean up NULL yet again.  */
  39
  40 # if !(defined _@GUARD_PREFIX@_STDDEF_H && defined _@GUARD_PREFIX@_STDDEF_WINT_T)
  41 #  ifdef __need_wint_t
  42 #   define _@GUARD_PREFIX@_STDDEF_WINT_T
  43 #  endif
  44 #  @INCLUDE_NEXT@ @NEXT_STDDEF_H@
  45    /* On TinyCC, make sure that the macros that indicate the special invocation
  46       convention get undefined.  */
  47 #  undef __need_wchar_t
  48 #  undef __need_size_t
  49 #  undef __need_ptrdiff_t
  50 #  undef __need_NULL
  51 #  undef __need_wint_t
  52 # endif
  53
  54 #else
  55 /* Normal invocation convention.  */
  56
  57 # ifndef _@GUARD_PREFIX@_STDDEF_H
  58
  59 /* On AIX 7.2, with xlc in 64-bit mode, <stddef.h> defines max_align_t to a
  60    type with alignment 4, but 'long' has alignment 8.  */
  61 #  if defined _AIX && defined __LP64__ && !@HAVE_MAX_ALIGN_T@
  62 #   if !GNULIB_defined_max_align_t
  63 #    ifdef _MAX_ALIGN_T
  64 /* /usr/include/stddef.h has already defined max_align_t.  Override it.  */
  65 typedef long rpl_max_align_t;
  66 #     define max_align_t rpl_max_align_t
  67 #    else
  68 /* Prevent /usr/include/stddef.h from defining max_align_t.  */
  69 typedef long max_align_t;
  70 #     define _MAX_ALIGN_T
  71 #    endif
  72 #    define __CLANG_MAX_ALIGN_T_DEFINED
  73 #    define GNULIB_defined_max_align_t 1
  74 #   endif
  75 #  endif
  76
  77 /* The include_next requires a split double-inclusion guard.  */
  78
  79 #  @INCLUDE_NEXT@ @NEXT_STDDEF_H@
  80
  81 /* On NetBSD 5.0, the definition of NULL lacks proper parentheses.  */
  82 #  if (@REPLACE_NULL@ \
  83        && (!defined _@GUARD_PREFIX@_STDDEF_H || defined _@GUARD_PREFIX@_STDDEF_WINT_T))
  84 #   undef NULL
  85 #   ifdef __cplusplus
  86    /* ISO C++ says that the macro NULL must expand to an integer constant
  87       expression, hence '((void *) 0)' is not allowed in C++.  */
  88 #    if __GNUG__ >= 3
  89     /* GNU C++ has a __null macro that behaves like an integer ('int' or
  90        'long') but has the same size as a pointer.  Use that, to avoid
  91        warnings.  */
  92 #     define NULL __null
  93 #    else
  94 #     define NULL 0L
  95 #    endif
  96 #   else
  97 #    define NULL ((void *) 0)
  98 #   endif
  99 #  endif
 100
 101 #  ifndef _@GUARD_PREFIX@_STDDEF_H
 102 #   define _@GUARD_PREFIX@_STDDEF_H
 103
 104 /* This file uses _Noreturn, _GL_ATTRIBUTE_NOTHROW.  */
 105 #if !_GL_CONFIG_H_INCLUDED
 106  #error "Please include config.h first."
 107 #endif
 108
 109 /* _GL_ATTRIBUTE_NOTHROW declares that the function does not throw exceptions.
 110  */
 111 #ifndef _GL_ATTRIBUTE_NOTHROW
 112 # if defined __cplusplus
 113 #  if (__GNUC__ + (__GNUC_MINOR__ >= 8) > 2) || __clang_major >= 4
 114 #   if __cplusplus >= 201103L
 115 #    define _GL_ATTRIBUTE_NOTHROW noexcept (true)
 116 #   else
 117 #    define _GL_ATTRIBUTE_NOTHROW throw ()
 118 #   endif
 119 #  else
 120 #   define _GL_ATTRIBUTE_NOTHROW
 121 #  endif
 122 # else
 123 #  if (__GNUC__ + (__GNUC_MINOR__ >= 3) > 3) || defined __clang__
 124 #   define _GL_ATTRIBUTE_NOTHROW __attribute__ ((__nothrow__))
 125 #  else
 126 #   define _GL_ATTRIBUTE_NOTHROW
 127 #  endif
 128 # endif
 129 #endif
 130
 131 /* Some platforms lack wchar_t.  */
 132 #if !@HAVE_WCHAR_T@
 133 # define wchar_t int
 134 #endif
 135
 136 /* Some platforms lack max_align_t.  The check for _GCC_MAX_ALIGN_T is
 137    a hack in case the configure-time test was done with g++ even though
 138    we are currently compiling with gcc.
 139    On MSVC, max_align_t is defined only in C++ mode, after <cstddef> was
 140    included.  Its definition is good since it has an alignment of 8 (on x86
 141    and x86_64).
 142    Similarly on OS/2 kLIBC.  */
 143 #if (defined _MSC_VER || (defined __KLIBC__ && !defined __LIBCN__)) \
 144     && defined __cplusplus
 145 # include <cstddef>
 146 #else
 147 # if ! (@HAVE_MAX_ALIGN_T@ || (defined _GCC_MAX_ALIGN_T && !defined __clang__))
 148 #  if !GNULIB_defined_max_align_t
 149 /* On the x86, the maximum storage alignment of double, long, etc. is 4,
 150    but GCC's C11 ABI for x86 says that max_align_t has an alignment of 8,
 151    and the C11 standard allows this.  Work around this problem by
 152    using __alignof__ (which returns 8 for double) rather than _Alignof
 153    (which returns 4), and align each union member accordingly.  */
 154 #   if defined __GNUC__ || (__clang_major__ >= 4)
 155 #    define _GL_STDDEF_ALIGNAS(type) \
 156        __attribute__ ((__aligned__ (__alignof__ (type))))
 157 #   else
 158 #    define _GL_STDDEF_ALIGNAS(type) /* */
 159 #   endif
 160 typedef union
 161 {
 162   char *__p _GL_STDDEF_ALIGNAS (char *);
 163   double __d _GL_STDDEF_ALIGNAS (double);
 164   long double __ld _GL_STDDEF_ALIGNAS (long double);
 165   long int __i _GL_STDDEF_ALIGNAS (long int);
 166 } rpl_max_align_t;
 167 #   define max_align_t rpl_max_align_t
 168 #   define __CLANG_MAX_ALIGN_T_DEFINED
 169 #   define GNULIB_defined_max_align_t 1
 170 #  endif
 171 # endif
 172 #endif
 173
 174 /* ISO C 23 § 7.21.1 The unreachable macro  */
 175 #ifndef unreachable
 176
 177 /* Code borrowed from verify.h.  */
 178 # ifndef _GL_HAS_BUILTIN_UNREACHABLE
 179 #  if defined __clang_major__ && __clang_major__ < 5
 180 #   define _GL_HAS_BUILTIN_UNREACHABLE 0
 181 #  elif 4 < __GNUC__ + (5 <= __GNUC_MINOR__)
 182 #   define _GL_HAS_BUILTIN_UNREACHABLE 1
 183 #  elif defined __has_builtin
 184 #   define _GL_HAS_BUILTIN_UNREACHABLE __has_builtin (__builtin_unreachable)
 185 #  else
 186 #   define _GL_HAS_BUILTIN_UNREACHABLE 0
 187 #  endif
 188 # endif
 189
 190 # if _GL_HAS_BUILTIN_UNREACHABLE
 191 #  define unreachable() __builtin_unreachable ()
 192 # elif 1200 <= _MSC_VER
 193 #  define unreachable() __assume (0)
 194 # else
 195 /* Declare abort(), without including <stdlib.h>.  */
 196 extern
 197 #  if defined __cplusplus
 198 "C"
 199 #  endif
 200 _Noreturn
 201 void abort (void)
 202 #  if defined __cplusplus && (__GLIBC__ >= 2)
 203 _GL_ATTRIBUTE_NOTHROW
 204 #  endif
 205 ;
 206 #  define unreachable() abort ()
 207 # endif
 208
 209 #endif
 210
 211 #  endif /* _@GUARD_PREFIX@_STDDEF_H */
 212 # endif /* _@GUARD_PREFIX@_STDDEF_H */
 213 #endif /* __need_XXX */