1# Check for stdalign.h that conforms to C11. 2 3dnl Copyright 2011-2014 Free Software Foundation, Inc. 4dnl This file is free software; the Free Software Foundation 5dnl gives unlimited permission to copy and/or distribute it, 6dnl with or without modifications, as long as this notice is preserved. 7 8# Prepare for substituting <stdalign.h> if it is not supported. 9 10AC_DEFUN([gl_STDALIGN_H], 11[ 12 AC_CACHE_CHECK([for working stdalign.h], 13 [gl_cv_header_working_stdalign_h], 14 [AC_COMPILE_IFELSE( 15 [AC_LANG_PROGRAM( 16 [[#include <stdalign.h> 17 #include <stddef.h> 18 19 /* Test that alignof yields a result consistent with offsetof. 20 This catches GCC bug 52023 21 <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023>. */ 22 #ifdef __cplusplus 23 template <class t> struct alignof_helper { char a; t b; }; 24 # define ao(type) offsetof (alignof_helper<type>, b) 25 #else 26 # define ao(type) offsetof (struct { char a; type b; }, b) 27 #endif 28 char test_double[ao (double) % _Alignof (double) == 0 ? 1 : -1]; 29 char test_long[ao (long int) % _Alignof (long int) == 0 ? 1 : -1]; 30 char test_alignof[alignof (double) == _Alignof (double) ? 1 : -1]; 31 32 /* Test _Alignas only on platforms where gnulib can help. */ 33 #if \ 34 ((defined __cplusplus && 201103 <= __cplusplus) \ 35 || __GNUC__ || __IBMC__ || __IBMCPP__ || __ICC \ 36 || 0x5110 <= __SUNPRO_C || 1300 <= _MSC_VER) 37 struct alignas_test { char c; char alignas (8) alignas_8; }; 38 char test_alignas[offsetof (struct alignas_test, alignas_8) == 8 39 ? 1 : -1]; 40 #endif 41 ]])], 42 [gl_cv_header_working_stdalign_h=yes], 43 [gl_cv_header_working_stdalign_h=no])]) 44 45 if test $gl_cv_header_working_stdalign_h = yes; then 46 STDALIGN_H='' 47 else 48 STDALIGN_H='stdalign.h' 49 fi 50 51 AC_SUBST([STDALIGN_H]) 52 AM_CONDITIONAL([GL_GENERATE_STDALIGN_H], [test -n "$STDALIGN_H"]) 53]) 54