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# Check for stdalign.h that conforms to C11.
dnl Copyright 2011-2020 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.
# Prepare for substituting <stdalign.h> if it is not supported.
AC_DEFUN([gl_STDALIGN_H],
[
AC_CACHE_CHECK([for working stdalign.h],
[gl_cv_header_working_stdalign_h],
[AC_COMPILE_IFELSE(
[AC_LANG_PROGRAM(
[[#include <stdalign.h>
#include <stddef.h>
/* Test that alignof yields a result consistent with offsetof.
This catches GCC bug 52023
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023>. */
#ifdef __cplusplus
template <class t> struct alignof_helper { char a; t b; };
# define ao(type) offsetof (alignof_helper<type>, b)
#else
# define ao(type) offsetof (struct { char a; type b; }, b)
#endif
char test_double[ao (double) % _Alignof (double) == 0 ? 1 : -1];
char test_long[ao (long int) % _Alignof (long int) == 0 ? 1 : -1];
char test_alignof[alignof (double) == _Alignof (double) ? 1 : -1];
/* Test _Alignas only on platforms where gnulib can help. */
#if \
((defined __cplusplus && 201103 <= __cplusplus) \
|| (defined __APPLE__ && defined __MACH__ \
? 4 < __GNUC__ + (1 <= __GNUC_MINOR__) \
: __GNUC__) \
|| (__ia64 && (61200 <= __HP_cc || 61200 <= __HP_aCC)) \
|| __ICC || 0x590 <= __SUNPRO_C || 0x0600 <= __xlC__ \
|| 1300 <= _MSC_VER)
struct alignas_test { char c; char alignas (8) alignas_8; };
char test_alignas[offsetof (struct alignas_test, alignas_8) == 8
? 1 : -1];
#endif
]])],
[gl_cv_header_working_stdalign_h=yes],
[gl_cv_header_working_stdalign_h=no])])
if test $gl_cv_header_working_stdalign_h = yes; then
STDALIGN_H=''
else
STDALIGN_H='stdalign.h'
fi
AC_SUBST([STDALIGN_H])
AM_CONDITIONAL([GL_GENERATE_STDALIGN_H], [test -n "$STDALIGN_H"])
])

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