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-rw-r--r--gl/m4/stdalign.m453
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1# Check for stdalign.h that conforms to C11.
2
3dnl Copyright 2011-2013 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])