-# Check for stdalign.h that conforms to C1x.
+# Check for stdalign.h that conforms to C11.
-dnl Copyright 2011 Free Software Foundation, Inc.
+dnl Copyright 2011-2013 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_STDALIGN_H],
[
- AC_CHECK_HEADERS_ONCE([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>
- if test $ac_cv_header_stdalign_h = yes; then
+ /* Test that alignof yields a result consistent with offsetof.
+ This catches GCC bug 52023
+ <http://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) \
+ || __GNUC__ || __IBMC__ || __IBMCPP__ || __ICC \
+ || 0x5110 <= __SUNPRO_C || 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'