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f0007cad | 1 | # Check for stdalign.h that conforms to C11. |
7f1ea859 | 2 | |
5e69ceb7 | 3 | dnl Copyright 2011-2014 Free Software Foundation, Inc. |
7f1ea859 LC |
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> | |
005de2e8 LC |
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]; | |
7f1ea859 LC |
31 | |
32 | /* Test _Alignas only on platforms where gnulib can help. */ | |
33 | #if \ | |
5e69ceb7 MW |
34 | ((defined __cplusplus && 201103 <= __cplusplus) \ |
35 | || __GNUC__ || __IBMC__ || __IBMCPP__ || __ICC \ | |
7f1ea859 | 36 | || 0x5110 <= __SUNPRO_C || 1300 <= _MSC_VER) |
5e69ceb7 MW |
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]; | |
7f1ea859 LC |
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 | ]) |