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# stddef_h.m4 serial 14
dnl Copyright (C) 2009-2024 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_ONCE([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])
GL_GENERATE_STDDEF_H=false
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(
[[/* On FreeBSD 12.0/x86, max_align_t defined by <stddef.h> has
the correct alignment with the default (wrong) definition of
_Alignof, but a wrong alignment as soon as we activate an
ISO C compliant _Alignof definition. */
#if ((defined __GNUC__ && 4 <= __GNUC__) || defined __clang__) && !defined __cplusplus
#define _Alignof(type) __builtin_offsetof (struct { char __a; type __b; }, __b)
#endif
#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
GL_GENERATE_STDDEF_H=true
fi
if test $gt_cv_c_wchar_t = no; then
HAVE_WCHAR_T=0
GL_GENERATE_STDDEF_H=true
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
GL_GENERATE_STDDEF_H=true
fi
AC_CACHE_CHECK([for unreachable],
[gl_cv_func_unreachable],
[AC_LINK_IFELSE(
[AC_LANG_PROGRAM(
[[#include <stddef.h>
]],
[[unreachable ();
]])],
[gl_cv_func_unreachable=yes],
[gl_cv_func_unreachable=no])
])
if test $gl_cv_func_unreachable = no; then
GL_GENERATE_STDDEF_H=true
fi
if $GL_GENERATE_STDDEF_H; then
gl_NEXT_HEADERS([stddef.h])
fi
])
# gl_STDDEF_MODULE_INDICATOR([modulename])
# sets the shell variable that indicates the presence of the given module
# to a C preprocessor expression that will evaluate to 1.
# This macro invocation must not occur in macros that are AC_REQUIREd.
AC_DEFUN([gl_STDDEF_MODULE_INDICATOR],
[
dnl Ensure to expand the default settings once only.
gl_STDDEF_H_REQUIRE_DEFAULTS
gl_MODULE_INDICATOR_SET_VARIABLE([$1])
])
# Initializes the default values for AC_SUBSTed shell variables.
# This macro must not be AC_REQUIREd. It must only be invoked, and only
# outside of macros or in macros that are not AC_REQUIREd.
AC_DEFUN([gl_STDDEF_H_REQUIRE_DEFAULTS],
[
m4_defun(GL_MODULE_INDICATOR_PREFIX[_STDDEF_H_MODULE_INDICATOR_DEFAULTS], [
])
m4_require(GL_MODULE_INDICATOR_PREFIX[_STDDEF_H_MODULE_INDICATOR_DEFAULTS])
AC_REQUIRE([gl_STDDEF_H_DEFAULTS])
])
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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