-/* A substitute for ISO C 1x <stdalign.h>.
+/* A substitute for ISO C11 <stdalign.h>.
- Copyright 2011 Free Software Foundation, Inc.
+ Copyright 2011-2014 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
- along with this program; if not, write to the Free Software Foundation,
- Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
+ along with this program; if not, see <http://www.gnu.org/licenses/>. */
/* Written by Paul Eggert and Bruno Haible. */
#ifndef _GL_STDALIGN_H
#define _GL_STDALIGN_H
-/* ISO C1X <stdalign.h> for platforms that lack it.
+/* ISO C11 <stdalign.h> for platforms that lack it.
References:
- ISO C1X <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf>
+ ISO C11 (latest free draft
+ <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf>)
sections 6.5.3.4, 6.7.5, 7.15.
- C++0X <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf>
+ C++11 (latest free draft
+ <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf>)
section 18.10. */
-/* Return the alignment of a structure slot (field) of TYPE,
- as an integer constant expression. 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.
+/* 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 is not the same as GCC's __alignof__ operator; for example, on
- x86 with GCC, _Alignof (long long) is typically 4 whereas
- __alignof__ (long long) is 8. */
+ This differs from GCC's __alignof__ operator, which can yield a
+ better-performing alignment for an object of that type. For
+ example, on x86 with GCC, __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.
+
+ Include <stddef.h> for offsetof. */
#include <stddef.h>
-#if defined __cplusplus
+
+/* FreeBSD 9.1 <sys/cdefs.h>, included by <stddef.h> and lots of other
+ standard headers, defines conflicting implementations of _Alignas
+ and _Alignof that are no better than ours; override them. */
+#undef _Alignas
+#undef _Alignof
+
+#if !defined __STDC_VERSION__ || __STDC_VERSION__ < 201112
+# ifdef __cplusplus
+# if 201103 <= __cplusplus
+# define _Alignof(type) alignof (type)
+# else
template <class __t> struct __alignof_helper { char __a; __t __b; };
-# define _Alignof(type) offsetof (__alignof_helper<type>, __b)
-#else
-# define _Alignof(type) offsetof (struct { char __a; type __b; }, __b)
+# define _Alignof(type) offsetof (__alignof_helper<type>, __b)
+# endif
+# else
+# define _Alignof(type) offsetof (struct { char __a; type __b; }, __b)
+# endif
#endif
#define alignof _Alignof
#define __alignof_is_defined 1
-/* Align a type or variable to the alignment A. */
-#if @HAVE_ATTRIBUTE_ALIGNED@ && !defined __cplusplus
-# define _Alignas(a) __attribute__ ((__aligned__ (a)))
-#elif 1300 <= _MSC_VER
-# define _Alignas(a) __declspec ((align (a)))
+/* 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 C11 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
+# define _Alignas(a) alignas (a)
+# elif __GNUC__ || __IBMC__ || __IBMCPP__ || __ICC || 0x5110 <= __SUNPRO_C
+# define _Alignas(a) __attribute__ ((__aligned__ (a)))
+# elif 1300 <= _MSC_VER
+# define _Alignas(a) __declspec (align (a))
+# endif
#endif
-#ifdef _Alignas
+#if defined _Alignas || (defined __STDC_VERSION && 201112 <= __STDC_VERSION__)
# define alignas _Alignas
# define __alignas_is_defined 1
#endif
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