lib/stddef.in.h

/* A substitute for POSIX 2008 <stddef.h>, for platforms that have issues.

   Copyright (C) 2009-2026 Free Software Foundation, Inc.

   This file is free software: you can redistribute it and/or modify
   it under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.

   This file is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

/* Written by Eric Blake.  */

/*
 * POSIX 2008 and ISO C 23 <stddef.h> for platforms that have issues.
 * <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/stddef.h.html>
 */

#if __GNUC__ >= 3
@PRAGMA_SYSTEM_HEADER@
#endif
@PRAGMA_COLUMNS@

#if (defined __need_wchar_t || defined __need_size_t                \
     || defined __need_ptrdiff_t || defined __need_NULL             \
     || defined __need_wint_t)                                      \
    /* Avoid warning triggered by "gcc -std=gnu23 -Wsystem-headers" \
       in GCC 13.3 and 14.2                                         \
       <https://gcc.gnu.org/PR114870>.  */   \
    && !@STDDEF_NOT_IDEMPOTENT@
/* Special invocation convention inside gcc header files.  In
   particular, <stddef.h> in some ancient versions of GCC blindly
   redefined NULL when __need_wint_t was defined, even though wint_t
   is not normally provided by <stddef.h>.
   (FIXME: It's not clear what GCC versions those were - perhaps so
   ancient that we can stop worrying about this?)
   Although glibc 2.26 (2017) and later do not use __need_wint_t,
   for portability to macOS, Cygwin, Haiku, and older Glibc + GCC,
   remember if special invocation has ever been used to obtain wint_t,
   in which case we need to clean up NULL yet again.  */

# if !(defined _@GUARD_PREFIX@_STDDEF_H && defined _@GUARD_PREFIX@_STDDEF_WINT_T)
#  ifdef __need_wint_t
#   define _@GUARD_PREFIX@_STDDEF_WINT_T
#  endif
#  @INCLUDE_NEXT@ @NEXT_STDDEF_H@
   /* On TinyCC, make sure that the macros that indicate the special invocation
      convention get undefined.  */
#  undef __need_wchar_t
#  undef __need_size_t
#  undef __need_ptrdiff_t
#  undef __need_NULL
#  undef __need_wint_t
# endif

#else
/* For @STDDEF_NOT_IDEMPOTENT@.  */
# undef __need_wchar_t
# undef __need_size_t
# undef __need_ptrdiff_t
# undef __need_NULL
# undef __need_wint_t

/* Normal invocation convention.  */

# ifndef _@GUARD_PREFIX@_STDDEF_H

/* On AIX 7.2, with xlc in 64-bit mode, <stddef.h> defines max_align_t to a
   type with alignment 4, but 'long' has alignment 8.  */
#  if defined _AIX && defined __LP64__ && !@HAVE_MAX_ALIGN_T@
#   if !GNULIB_defined_max_align_t
#    ifdef _MAX_ALIGN_T
/* /usr/include/stddef.h has already defined max_align_t.  Override it.  */
typedef long rpl_max_align_t;
#     define max_align_t rpl_max_align_t
#    else
/* Prevent /usr/include/stddef.h from defining max_align_t.  */
typedef long max_align_t;
#     define _MAX_ALIGN_T
#    endif
#    define __CLANG_MAX_ALIGN_T_DEFINED
#    define GNULIB_defined_max_align_t 1
#   endif
#  endif

#  if !defined _GCC_NULLPTR_T && !@NULLPTR_T_NEEDS_STDDEF@
    /* Suppress unwanted nullptr_t typedef.  See
       <https://gcc.gnu.org/PR114869>.  */
#   define _GCC_NULLPTR_T
#  endif

/* The include_next requires a split double-inclusion guard.  */

#  @INCLUDE_NEXT@ @NEXT_STDDEF_H@

/* On NetBSD 5.0, the definition of NULL lacks proper parentheses.  */
#  if (@REPLACE_NULL@ \
       && (!defined _@GUARD_PREFIX@_STDDEF_H || defined _@GUARD_PREFIX@_STDDEF_WINT_T))
#   undef NULL
#   ifdef __cplusplus
   /* ISO C++ says that the macro NULL must expand to an integer constant
      expression, hence '((void *) 0)' is not allowed in C++.  */
#    if __GNUG__ >= 3
    /* GNU C++ has a __null macro that behaves like an integer ('int' or
       'long') but has the same size as a pointer.  Use that, to avoid
       warnings.  */
#     define NULL __null
#    else
#     define NULL 0L
#    endif
#   else
#    define NULL ((void *) 0)
#   endif
#  endif

#  ifndef _@GUARD_PREFIX@_STDDEF_H
#   define _@GUARD_PREFIX@_STDDEF_H

/* This file uses _Noreturn, _GL_ATTRIBUTE_NOTHROW.  */
#if !_GL_CONFIG_H_INCLUDED
 #error "Please include config.h first."
#endif

/* _GL_ATTRIBUTE_NOTHROW declares that the function does not throw exceptions.
 */
#ifndef _GL_ATTRIBUTE_NOTHROW
# if defined __cplusplus
#  if (__GNUC__ + (__GNUC_MINOR__ >= 8) > 2) || __clang_major__ >= 4
#   if __cplusplus >= 201103L
#    define _GL_ATTRIBUTE_NOTHROW noexcept (true)
#   else
#    define _GL_ATTRIBUTE_NOTHROW throw ()
#   endif
#  else
#   define _GL_ATTRIBUTE_NOTHROW
#  endif
# else
#  if (__GNUC__ + (__GNUC_MINOR__ >= 3) > 3) || defined __clang__
#   define _GL_ATTRIBUTE_NOTHROW __attribute__ ((__nothrow__))
#  else
#   define _GL_ATTRIBUTE_NOTHROW
#  endif
# endif
#endif

/* Some platforms lack max_align_t.  The check for _GCC_MAX_ALIGN_T is
   a hack in case the configure-time test was done with g++ even though
   we are currently compiling with gcc.
   On MSVC, max_align_t is defined only in C++ mode, after <cstddef> was
   included.  Its definition is good since it has an alignment of 8 (on x86
   and x86_64).
   Similarly on OS/2 kLIBC.  */
#if (defined _MSC_VER || (defined __KLIBC__ && !defined __LIBCN__)) \
    && defined __cplusplus
# include <cstddef>
#else
# if ! (@HAVE_MAX_ALIGN_T@ || (defined _GCC_MAX_ALIGN_T && !defined __clang__))
#  if !GNULIB_defined_max_align_t
/* On the x86, the maximum storage alignment of double, long, etc. is 4,
   but GCC's C11 ABI for x86 says that max_align_t has an alignment of 8,
   and the C11 standard allows this.  Work around this problem by
   using __alignof__ (which returns 8 for double) rather than _Alignof
   (which returns 4), and align each union member accordingly.  */
#   if defined __GNUC__ || (__clang_major__ >= 4)
#    define _GL_STDDEF_ALIGNAS(type) \
       __attribute__ ((__aligned__ (__alignof__ (type))))
#   else
#    define _GL_STDDEF_ALIGNAS(type) /* */
#   endif
typedef union
{
  char *__p _GL_STDDEF_ALIGNAS (char *);
  double __d _GL_STDDEF_ALIGNAS (double);
  long double __ld _GL_STDDEF_ALIGNAS (long double);
  long int __i _GL_STDDEF_ALIGNAS (long int);
} rpl_max_align_t;
#   define max_align_t rpl_max_align_t
#   define __CLANG_MAX_ALIGN_T_DEFINED
#   define GNULIB_defined_max_align_t 1
#  endif
# endif
#endif

/* ISO C 23 § 7.21.1 The unreachable macro  */
/* This macro is only usable in C, not in C++.
   There is no way to define it as a macro in C++, because that would break code
   that does
       #include <utility>
       ... std::unreachable() ...
   Similarly, there is no way to define it as an inline function in C++, because
   that would break code that does
       #include <utility>
       using std::unreachable;
   As a workaround, we define a macro gl_unreachable, that is like unreachable,
   but is usable in both C and C++.  */

/* Code borrowed from verify.h.  */
#ifndef _GL_HAS_BUILTIN_UNREACHABLE
# if defined __clang_major__ && __clang_major__ < 5
#  define _GL_HAS_BUILTIN_UNREACHABLE 0
# elif 4 < __GNUC__ + (5 <= __GNUC_MINOR__) && !defined __clang__
#  define _GL_HAS_BUILTIN_UNREACHABLE 1
# elif defined __has_builtin
#  define _GL_HAS_BUILTIN_UNREACHABLE __has_builtin (__builtin_unreachable)
# else
#  define _GL_HAS_BUILTIN_UNREACHABLE 0
# endif
#endif

#if _GL_HAS_BUILTIN_UNREACHABLE
# define gl_unreachable() __builtin_unreachable ()
#elif 1200 <= _MSC_VER
# define gl_unreachable() __assume (0)
#elif !defined __cplusplus && @HAVE_C_UNREACHABLE@
# define gl_unreachable() unreachable ()
#else
/* Declare abort(), without including <stdlib.h>.  */
extern
# if defined __cplusplus
"C"
# endif
_Noreturn
void abort (void)
# if defined __cplusplus && (__GLIBC__ >= 2)
_GL_ATTRIBUTE_NOTHROW
# endif
;
# define gl_unreachable() abort ()
#endif

#if !defined __cplusplus && !@HAVE_C_UNREACHABLE@
/* In C, define unreachable as a macro.  */

# ifndef unreachable
#  define unreachable() gl_unreachable ()
# endif

#endif

#  endif /* _@GUARD_PREFIX@_STDDEF_H */
# endif /* _@GUARD_PREFIX@_STDDEF_H */
#endif /* __need_XXX */