1 # Check for stdalign.h that conforms to C11.
3 dnl Copyright 2011-2012 Free Software Foundation, Inc.
4 dnl This file is free software; the Free Software Foundation
5 dnl gives unlimited permission to copy and/or distribute it,
6 dnl with or without modifications, as long as this notice is preserved.
8 # Prepare for substituting <stdalign.h> if it is not supported.
10 AC_DEFUN([gl_STDALIGN_H],
12 AC_CACHE_CHECK([for working stdalign.h],
13 [gl_cv_header_working_stdalign_h],
16 [[#include <stdalign.h>
19 /* Test that alignof yields a result consistent with offsetof.
20 This catches GCC bug 51316
21 <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51316>. */
23 template <class t> struct alignof_helper { char a; t b; };
24 # define ao(type) offsetof (alignof_helper<type>, b)
26 # define ao(type) offsetof (struct { char a; type b; }, b)
28 char test1[_Alignof (double) == ao (double) ? 1 : -1];
29 char test2[alignof (long int) == ao (long int) ? 1 : -1];
31 /* Test _Alignas only on platforms where gnulib can help. */
33 (__GNUC__ || __IBMC__ || __IBMCPP__ \
34 || 0x5110 <= __SUNPRO_C || 1300 <= _MSC_VER)
35 int alignas (8) alignas_int = 1;
36 char test3[8 <= _Alignof (alignas_int) ? 1 : -1];
39 [gl_cv_header_working_stdalign_h=yes],
40 [gl_cv_header_working_stdalign_h=no])])
42 if test $gl_cv_header_working_stdalign_h = yes; then
45 STDALIGN_H='stdalign.h'
48 AC_SUBST([STDALIGN_H])
49 AM_CONDITIONAL([GL_GENERATE_STDALIGN_H], [test -n "$STDALIGN_H"])