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# Check for nullptr that conforms to C23 and C++11.
dnl Copyright 2023 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
AC_DEFUN([gl_NULLPTR],
[
m4_provide_if([AC_PROG_CC],
[AC_LANG_PUSH([C])
AC_CACHE_CHECK([for C nullptr], [gl_cv_c_nullptr],
[AC_COMPILE_IFELSE(
[AC_LANG_SOURCE([[int *p = nullptr;]])],
[gl_cv_c_nullptr=yes],
[gl_cv_c_nullptr=no])])
gl_c_nullptr=$gl_cv_c_nullptr
AC_LANG_POP([C])],
[gl_c_nullptr=no])
if test "$gl_c_nullptr" = yes; then
AC_DEFINE([HAVE_C_NULLPTR], [1],
[Define to 1 if C nullptr is known to work.])
fi
m4_provide_if([AC_PROG_CXX],
[AC_LANG_PUSH([C++])
AC_CACHE_CHECK([for C++ nullptr], [gl_cv_cxx_nullptr],
[AC_COMPILE_IFELSE(
[AC_LANG_SOURCE([[int *p = nullptr;]])],
[gl_cv_cxx_nullptr=yes],
[AC_COMPILE_IFELSE(
[AC_LANG_SOURCE([[#include <stddef.h>
int *p = nullptr;]])],
[gl_cv_cxx_nullptr="yes, but it is a <stddef.h> macro"],
[gl_cv_cxx_nullptr=no])])])
AS_CASE([$gl_cv_cxx_nullptr],
[yes], [gl_have_cxx_nullptr=1],
[yes*], [gl_have_cxx_nullptr="(-1)"],
[gl_have_cxx_nullptr=0])
AC_DEFINE_UNQUOTED([HAVE_CXX_NULLPTR], [$gl_have_cxx_nullptr],
[Define to 1 if C++ nullptr works, 0 if not,
(-1) if it is a <stddef.h> macro.])
AC_LANG_POP([C++])])
])
AH_VERBATIM([zznullptr],
[#if defined __cplusplus && HAVE_CXX_NULLPTR < 0
# include <stddef.h>
# undef/**/nullptr
#endif
#ifndef nullptr
# if !defined __cplusplus && !defined HAVE_C_NULLPTR
# define nullptr ((void *) 0)
# elif defined __cplusplus && HAVE_CXX_NULLPTR <= 0
# if 3 <= __GNUG__
# define nullptr __null
# else
# define nullptr 0L
# endif
# endif
#endif])
])
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