1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
|
# Check for alignas and alignof that conform to C23.
dnl Copyright 2011-2024 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.
dnl Written by Paul Eggert and Bruno Haible.
# Prepare for substituting <stdalign.h> if it is not supported.
AC_DEFUN([gl_ALIGNASOF],
[
AC_CACHE_CHECK([for alignas and alignof],
[gl_cv_header_working_stdalign_h],
[gl_saved_CFLAGS=$CFLAGS
for gl_working in "yes, keywords" "yes, <stdalign.h> macros"; do
AS_CASE([$gl_working],
[*stdalign.h*], [CFLAGS="$gl_saved_CFLAGS -DINCLUDE_STDALIGN_H"])
AC_COMPILE_IFELSE(
[AC_LANG_PROGRAM(
[[#include <stdint.h>
#ifdef INCLUDE_STDALIGN_H
#include <stdalign.h>
#endif
#include <stddef.h>
/* Test that alignof yields a result consistent with offsetof.
This catches GCC bug 52023
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023>. */
#ifdef __cplusplus
template <class t> struct alignof_helper { char a; t b; };
# define ao(type) offsetof (alignof_helper<type>, b)
#else
# define ao(type) offsetof (struct { char a; type b; }, b)
#endif
char test_double[ao (double) % _Alignof (double) == 0 ? 1 : -1];
char test_long[ao (long int) % _Alignof (long int) == 0 ? 1 : -1];
char test_alignof[alignof (double) == _Alignof (double) ? 1 : -1];
/* Test alignas only on platforms where gnulib can help. */
#if \
((defined __cplusplus && 201103 <= __cplusplus) \
|| (__TINYC__ && defined __attribute__) \
|| (defined __APPLE__ && defined __MACH__ \
? 4 < __GNUC__ + (1 <= __GNUC_MINOR__) \
: __GNUC__) \
|| (__ia64 && (61200 <= __HP_cc || 61200 <= __HP_aCC)) \
|| __ICC || 0x590 <= __SUNPRO_C || 0x0600 <= __xlC__ \
|| 1300 <= _MSC_VER)
struct alignas_test { char c; char alignas (8) alignas_8; };
char test_alignas[offsetof (struct alignas_test, alignas_8) == 8
? 1 : -1];
#endif
]])],
[gl_cv_header_working_stdalign_h=$gl_working],
[gl_cv_header_working_stdalign_h=no])
CFLAGS=$gl_saved_CFLAGS
test "$gl_cv_header_working_stdalign_h" != no && break
done])
AS_CASE([$gl_cv_header_working_stdalign_h],
[yes*keyword*],
[AC_DEFINE([HAVE_C_ALIGNASOF], [1],
[Define to 1 if the alignas and alignof keywords work.])])
dnl The "zz" puts this toward config.h's end, to avoid potential
dnl collisions with other definitions.
AH_VERBATIM([zzalignas],
[#if !defined HAVE_C_ALIGNASOF \
&& !(defined __cplusplus && 201103 <= __cplusplus) \
&& !defined alignof
# if defined HAVE_STDALIGN_H
# include <stdalign.h>
# endif
/* ISO C23 alignas and alignof for platforms that lack it.
References:
ISO C23 (latest free draft
<http://www.open-std.org/jtc1/sc22/wg14/www/docs/n3047.pdf>)
sections 6.5.3.4, 6.7.5, 7.15.
C++11 (latest free draft
<http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf>)
section 18.10. */
/* alignof (TYPE), also known as _Alignof (TYPE), yields the alignment
requirement of a structure member (i.e., slot or field) that is of
type TYPE, as an integer constant expression.
This differs from GCC's and clang's __alignof__ operator, which can
yield a better-performing alignment for an object of that type. For
example, on x86 with GCC and on Linux/x86 with clang,
__alignof__ (double) and __alignof__ (long long) are 8, whereas
alignof (double) and alignof (long long) are 4 unless the option
'-malign-double' is used.
The result cannot be used as a value for an 'enum' constant, if you
want to be portable to HP-UX 10.20 cc and AIX 3.2.5 xlc. */
/* GCC releases before GCC 4.9 had a bug in _Alignof. See GCC bug 52023
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023>.
clang versions < 8.0.0 have the same bug. */
# if (!defined __STDC_VERSION__ || __STDC_VERSION__ < 201112 \
|| (defined __GNUC__ && __GNUC__ < 4 + (__GNUC_MINOR__ < 9) \
&& !defined __clang__) \
|| (defined __clang__ && __clang_major__ < 8))
# undef/**/_Alignof
# ifdef __cplusplus
# if (201103 <= __cplusplus || defined _MSC_VER)
# define _Alignof(type) alignof (type)
# else
template <class __t> struct __alignof_helper { char __a; __t __b; };
# if (defined __GNUC__ && 4 <= __GNUC__) || defined __clang__
# define _Alignof(type) __builtin_offsetof (__alignof_helper<type>, __b)
# else
# define _Alignof(type) offsetof (__alignof_helper<type>, __b)
# endif
# define _GL_STDALIGN_NEEDS_STDDEF 1
# endif
# else
# if (defined __GNUC__ && 4 <= __GNUC__) || defined __clang__
# define _Alignof(type) __builtin_offsetof (struct { char __a; type __b; }, __b)
# else
# define _Alignof(type) offsetof (struct { char __a; type __b; }, __b)
# define _GL_STDALIGN_NEEDS_STDDEF 1
# endif
# endif
# endif
# if ! (defined __cplusplus && (201103 <= __cplusplus || defined _MSC_VER))
# undef/**/alignof
# define alignof _Alignof
# endif
/* alignas (A), also known as _Alignas (A), aligns a variable or type
to the alignment A, where A is an integer constant expression. For
example:
int alignas (8) foo;
struct s { int a; int alignas (8) bar; };
aligns the address of FOO and the offset of BAR to be multiples of 8.
A should be a power of two that is at least the type's alignment
and at most the implementation's alignment limit. This limit is
2**28 on typical GNUish hosts, and 2**13 on MSVC. To be portable
to MSVC through at least version 10.0, A should be an integer
constant, as MSVC does not support expressions such as 1 << 3.
To be portable to Sun C 5.11, do not align auto variables to
anything stricter than their default alignment.
The following C23 requirements are not supported here:
- If A is zero, alignas has no effect.
- alignas can be used multiple times; the strictest one wins.
- alignas (TYPE) is equivalent to alignas (alignof (TYPE)).
*/
# if !defined __STDC_VERSION__ || __STDC_VERSION__ < 201112
# if defined __cplusplus && (201103 <= __cplusplus || defined _MSC_VER)
# define _Alignas(a) alignas (a)
# elif (!defined __attribute__ \
&& ((defined __APPLE__ && defined __MACH__ \
? 4 < __GNUC__ + (1 <= __GNUC_MINOR__) \
: __GNUC__ && !defined __ibmxl__) \
|| (4 <= __clang_major__) \
|| (__ia64 && (61200 <= __HP_cc || 61200 <= __HP_aCC)) \
|| __ICC || 0x590 <= __SUNPRO_C || 0x0600 <= __xlC__))
# define _Alignas(a) __attribute__ ((__aligned__ (a)))
# elif 1300 <= _MSC_VER
# define _Alignas(a) __declspec (align (a))
# endif
# endif
# if !defined HAVE_STDALIGN_H
# if ((defined _Alignas \
&& !(defined __cplusplus \
&& (201103 <= __cplusplus || defined _MSC_VER))) \
|| (defined __STDC_VERSION__ && 201112 <= __STDC_VERSION__))
# define alignas _Alignas
# endif
# endif
# if defined _GL_STDALIGN_NEEDS_STDDEF
# include <stddef.h>
# endif
#endif])
])
AC_DEFUN([gl_STDALIGN_H],
[
AC_REQUIRE([gl_ALIGNASOF])
if test "$gl_cv_header_working_stdalign_h" = no; then
GL_GENERATE_STDALIGN_H=true
else
GL_GENERATE_STDALIGN_H=false
fi
gl_CHECK_NEXT_HEADERS([stdalign.h])
if test $ac_cv_header_stdalign_h = yes; then
HAVE_STDALIGN_H=1
else
HAVE_STDALIGN_H=0
fi
AC_SUBST([HAVE_STDALIGN_H])
])
|
