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1 | # Check for stdalign.h that conforms to C11. |
2 | ||
3 | dnl Copyright 2011-2016 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. | |
7 | ||
8 | # Prepare for substituting <stdalign.h> if it is not supported. | |
9 | ||
10 | AC_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 | || (defined __APPLE__ && defined __MACH__ \ | |
36 | ? 4 < __GNUC__ + (1 <= __GNUC_MINOR__) \ | |
37 | : __GNUC__) \ | |
38 | || __HP_cc || __HP_aCC || __IBMC__ || __IBMCPP__ \ | |
39 | || __ICC || 0x5110 <= __SUNPRO_C \ | |
40 | || 1300 <= _MSC_VER) | |
41 | struct alignas_test { char c; char alignas (8) alignas_8; }; | |
42 | char test_alignas[offsetof (struct alignas_test, alignas_8) == 8 | |
43 | ? 1 : -1]; | |
44 | #endif | |
45 | ]])], | |
46 | [gl_cv_header_working_stdalign_h=yes], | |
47 | [gl_cv_header_working_stdalign_h=no])]) | |
48 | ||
49 | if test $gl_cv_header_working_stdalign_h = yes; then | |
50 | STDALIGN_H='' | |
51 | else | |
52 | STDALIGN_H='stdalign.h' | |
53 | fi | |
54 | ||
55 | AC_SUBST([STDALIGN_H]) | |
56 | AM_CONDITIONAL([GL_GENERATE_STDALIGN_H], [test -n "$STDALIGN_H"]) | |
57 | ]) |