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     /* Avoid warning triggered by "gcc -std=gnu23 -Wsystem-headers" \
  34        in Fedora 40 with gcc 14.0.1.                                \
  35        <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114870>.  */   \
  36     && !@STDDEF_NOT_IDEMPOTENT@
  37 /* Special invocation convention inside gcc header files.  In
  38    particular, <stddef.h> in some ancient versions of GCC blindly
  39    redefined NULL when __need_wint_t was defined, even though wint_t
  40    is not normally provided by <stddef.h>.
  41    (FIXME: It's not clear what GCC versions those were - perhaps so
  42    ancient that we can stop worrying about this?)
  43    Although glibc 2.26 (2017) and later do not use __need_wint_t,
  44    for portability to macOS, Cygwin, Haiku, and older Glibc + GCC,
  45    remember if special invocation has ever been used to obtain wint_t,
  46    in which case we need to clean up NULL yet again.  */
  47
  48 # if !(defined _@GUARD_PREFIX@_STDDEF_H && defined _@GUARD_PREFIX@_STDDEF_WINT_T)
  49 #  ifdef __need_wint_t
  50 #   define _@GUARD_PREFIX@_STDDEF_WINT_T
  51 #  endif
  52 #  @INCLUDE_NEXT@ @NEXT_STDDEF_H@
  53    /* On TinyCC, make sure that the macros that indicate the special invocation
  54       convention get undefined.  */
  55 #  undef __need_wchar_t
  56 #  undef __need_size_t
  57 #  undef __need_ptrdiff_t
  58 #  undef __need_NULL
  59 #  undef __need_wint_t
  60 # endif
  61
  62 #else
  63 /* For @STDDEF_NOT_IDEMPOTENT@.  */
  64 # undef __need_wchar_t
  65 # undef __need_size_t
  66 # undef __need_ptrdiff_t
  67 # undef __need_NULL
  68 # undef __need_wint_t
  69
  70 /* Normal invocation convention.  */
  71
  72 # ifndef _@GUARD_PREFIX@_STDDEF_H
  73
  74 /* On AIX 7.2, with xlc in 64-bit mode, <stddef.h> defines max_align_t to a
  75    type with alignment 4, but 'long' has alignment 8.  */
  76 #  if defined _AIX && defined __LP64__ && !@HAVE_MAX_ALIGN_T@
  77 #   if !GNULIB_defined_max_align_t
  78 #    ifdef _MAX_ALIGN_T
  79 /* /usr/include/stddef.h has already defined max_align_t.  Override it.  */
  80 typedef long rpl_max_align_t;
  81 #     define max_align_t rpl_max_align_t
  82 #    else
  83 /* Prevent /usr/include/stddef.h from defining max_align_t.  */
  84 typedef long max_align_t;
  85 #     define _MAX_ALIGN_T
  86 #    endif
  87 #    define __CLANG_MAX_ALIGN_T_DEFINED
  88 #    define GNULIB_defined_max_align_t 1
  89 #   endif
  90 #  endif
  91
  92 #  if !defined _GCC_NULLPTR_T && !@NULLPTR_T_NEEDS_STDDEF@
  93     /* Suppress unwanted nullptr_t typedef.  See
  94        <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114869>.  */
  95 #   define _GCC_NULLPTR_T
  96 #  endif
  97
  98 /* The include_next requires a split double-inclusion guard.  */
  99
 100 #  @INCLUDE_NEXT@ @NEXT_STDDEF_H@
 101
 102 /* On NetBSD 5.0, the definition of NULL lacks proper parentheses.  */
 103 #  if (@REPLACE_NULL@ \
 104        && (!defined _@GUARD_PREFIX@_STDDEF_H || defined _@GUARD_PREFIX@_STDDEF_WINT_T))
 105 #   undef NULL
 106 #   ifdef __cplusplus
 107    /* ISO C++ says that the macro NULL must expand to an integer constant
 108       expression, hence '((void *) 0)' is not allowed in C++.  */
 109 #    if __GNUG__ >= 3
 110     /* GNU C++ has a __null macro that behaves like an integer ('int' or
 111        'long') but has the same size as a pointer.  Use that, to avoid
 112        warnings.  */
 113 #     define NULL __null
 114 #    else
 115 #     define NULL 0L
 116 #    endif
 117 #   else
 118 #    define NULL ((void *) 0)
 119 #   endif
 120 #  endif
 121
 122 #  ifndef _@GUARD_PREFIX@_STDDEF_H
 123 #   define _@GUARD_PREFIX@_STDDEF_H
 124
 125 /* This file uses _Noreturn, _GL_ATTRIBUTE_NOTHROW.  */
 126 #if !_GL_CONFIG_H_INCLUDED
 127  #error "Please include config.h first."
 128 #endif
 129
 130 /* _GL_ATTRIBUTE_NOTHROW declares that the function does not throw exceptions.
 131  */
 132 #ifndef _GL_ATTRIBUTE_NOTHROW
 133 # if defined __cplusplus
 134 #  if (__GNUC__ + (__GNUC_MINOR__ >= 8) > 2) || __clang_major__ >= 4
 135 #   if __cplusplus >= 201103L
 136 #    define _GL_ATTRIBUTE_NOTHROW noexcept (true)
 137 #   else
 138 #    define _GL_ATTRIBUTE_NOTHROW throw ()
 139 #   endif
 140 #  else
 141 #   define _GL_ATTRIBUTE_NOTHROW
 142 #  endif
 143 # else
 144 #  if (__GNUC__ + (__GNUC_MINOR__ >= 3) > 3) || defined __clang__
 145 #   define _GL_ATTRIBUTE_NOTHROW __attribute__ ((__nothrow__))
 146 #  else
 147 #   define _GL_ATTRIBUTE_NOTHROW
 148 #  endif
 149 # endif
 150 #endif
 151
 152 /* Some platforms lack max_align_t.  The check for _GCC_MAX_ALIGN_T is
 153    a hack in case the configure-time test was done with g++ even though
 154    we are currently compiling with gcc.
 155    On MSVC, max_align_t is defined only in C++ mode, after <cstddef> was
 156    included.  Its definition is good since it has an alignment of 8 (on x86
 157    and x86_64).
 158    Similarly on OS/2 kLIBC.  */
 159 #if (defined _MSC_VER || (defined __KLIBC__ && !defined __LIBCN__)) \
 160     && defined __cplusplus
 161 # include <cstddef>
 162 #else
 163 # if ! (@HAVE_MAX_ALIGN_T@ || (defined _GCC_MAX_ALIGN_T && !defined __clang__))
 164 #  if !GNULIB_defined_max_align_t
 165 /* On the x86, the maximum storage alignment of double, long, etc. is 4,
 166    but GCC's C11 ABI for x86 says that max_align_t has an alignment of 8,
 167    and the C11 standard allows this.  Work around this problem by
 168    using __alignof__ (which returns 8 for double) rather than _Alignof
 169    (which returns 4), and align each union member accordingly.  */
 170 #   if defined __GNUC__ || (__clang_major__ >= 4)
 171 #    define _GL_STDDEF_ALIGNAS(type) \
 172        __attribute__ ((__aligned__ (__alignof__ (type))))
 173 #   else
 174 #    define _GL_STDDEF_ALIGNAS(type) /* */
 175 #   endif
 176 typedef union
 177 {
 178   char *__p _GL_STDDEF_ALIGNAS (char *);
 179   double __d _GL_STDDEF_ALIGNAS (double);
 180   long double __ld _GL_STDDEF_ALIGNAS (long double);
 181   long int __i _GL_STDDEF_ALIGNAS (long int);
 182 } rpl_max_align_t;
 183 #   define max_align_t rpl_max_align_t
 184 #   define __CLANG_MAX_ALIGN_T_DEFINED
 185 #   define GNULIB_defined_max_align_t 1
 186 #  endif
 187 # endif
 188 #endif
 189
 190 /* ISO C 23 § 7.21.1 The unreachable macro  */
 191 #ifndef unreachable
 192
 193 /* Code borrowed from verify.h.  */
 194 # ifndef _GL_HAS_BUILTIN_UNREACHABLE
 195 #  if defined __clang_major__ && __clang_major__ < 5
 196 #   define _GL_HAS_BUILTIN_UNREACHABLE 0
 197 #  elif 4 < __GNUC__ + (5 <= __GNUC_MINOR__) && !defined __clang__
 198 #   define _GL_HAS_BUILTIN_UNREACHABLE 1
 199 #  elif defined __has_builtin
 200 #   define _GL_HAS_BUILTIN_UNREACHABLE __has_builtin (__builtin_unreachable)
 201 #  else
 202 #   define _GL_HAS_BUILTIN_UNREACHABLE 0
 203 #  endif
 204 # endif
 205
 206 # if _GL_HAS_BUILTIN_UNREACHABLE
 207 #  define unreachable() __builtin_unreachable ()
 208 # elif 1200 <= _MSC_VER
 209 #  define unreachable() __assume (0)
 210 # else
 211 /* Declare abort(), without including <stdlib.h>.  */
 212 extern
 213 #  if defined __cplusplus
 214 "C"
 215 #  endif
 216 _Noreturn
 217 void abort (void)
 218 #  if defined __cplusplus && (__GLIBC__ >= 2)
 219 _GL_ATTRIBUTE_NOTHROW
 220 #  endif
 221 ;
 222 #  define unreachable() abort ()
 223 # endif
 224
 225 #endif
 226
 227 #  endif /* _@GUARD_PREFIX@_STDDEF_H */
 228 # endif /* _@GUARD_PREFIX@_STDDEF_H */
 229 #endif /* __need_XXX */