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# stddef_h.m4 serial 9
dnl Copyright (C) 2009-2021 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.
dnl A placeholder for <stddef.h>, for platforms that have issues.
AC_DEFUN([gl_STDDEF_H],
[
AC_REQUIRE([gl_STDDEF_H_DEFAULTS])
AC_REQUIRE([gt_TYPE_WCHAR_T])
dnl Persuade OpenBSD <stddef.h> to declare max_align_t.
AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
STDDEF_H=
dnl Test whether the type max_align_t exists and whether its alignment
dnl "is as great as is supported by the implementation in all contexts".
AC_CACHE_CHECK([for good max_align_t],
[gl_cv_type_max_align_t],
[AC_COMPILE_IFELSE(
[AC_LANG_PROGRAM(
[[#include <stddef.h>
unsigned int s = sizeof (max_align_t);
#if defined __GNUC__ || defined __clang__ || defined __IBM__ALIGNOF__
int check1[2 * (__alignof__ (double) <= __alignof__ (max_align_t)) - 1];
int check2[2 * (__alignof__ (long double) <= __alignof__ (max_align_t)) - 1];
#endif
typedef struct { char a; max_align_t b; } max_helper;
typedef struct { char a; long b; } long_helper;
typedef struct { char a; double b; } double_helper;
typedef struct { char a; long double b; } long_double_helper;
int check3[2 * (offsetof (long_helper, b) <= offsetof (max_helper, b)) - 1];
int check4[2 * (offsetof (double_helper, b) <= offsetof (max_helper, b)) - 1];
int check5[2 * (offsetof (long_double_helper, b) <= offsetof (max_helper, b)) - 1];
]])],
[gl_cv_type_max_align_t=yes],
[gl_cv_type_max_align_t=no])
])
if test $gl_cv_type_max_align_t = no; then
HAVE_MAX_ALIGN_T=0
STDDEF_H=stddef.h
fi
if test $gt_cv_c_wchar_t = no; then
HAVE_WCHAR_T=0
STDDEF_H=stddef.h
fi
AC_CACHE_CHECK([whether NULL can be used in arbitrary expressions],
[gl_cv_decl_null_works],
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <stddef.h>
int test[2 * (sizeof NULL == sizeof (void *)) -1];
]])],
[gl_cv_decl_null_works=yes],
[gl_cv_decl_null_works=no])])
if test $gl_cv_decl_null_works = no; then
REPLACE_NULL=1
STDDEF_H=stddef.h
fi
AC_SUBST([STDDEF_H])
AM_CONDITIONAL([GL_GENERATE_STDDEF_H], [test -n "$STDDEF_H"])
if test -n "$STDDEF_H"; then
gl_NEXT_HEADERS([stddef.h])
fi
])
AC_DEFUN([gl_STDDEF_MODULE_INDICATOR],
[
dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
AC_REQUIRE([gl_STDDEF_H_DEFAULTS])
gl_MODULE_INDICATOR_SET_VARIABLE([$1])
])
AC_DEFUN([gl_STDDEF_H_DEFAULTS],
[
dnl Assume proper GNU behavior unless another module says otherwise.
REPLACE_NULL=0; AC_SUBST([REPLACE_NULL])
HAVE_MAX_ALIGN_T=1; AC_SUBST([HAVE_MAX_ALIGN_T])
HAVE_WCHAR_T=1; AC_SUBST([HAVE_WCHAR_T])
])
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