mirror of
https://git.savannah.gnu.org/git/emacs.git
synced 2024-11-22 07:09:54 +00:00
127 lines
4.9 KiB
C++
127 lines
4.9 KiB
C++
/* A substitute for ISO C11 <stdalign.h>.
|
|
|
|
Copyright 2011-2021 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
|
|
the Free Software Foundation; either version 3, or (at your option)
|
|
any later version.
|
|
|
|
This program is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
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, see <https://www.gnu.org/licenses/>. */
|
|
|
|
/* Written by Paul Eggert and Bruno Haible. */
|
|
|
|
#ifndef _GL_STDALIGN_H
|
|
#define _GL_STDALIGN_H
|
|
|
|
/* ISO C11 <stdalign.h> for platforms that lack it.
|
|
|
|
References:
|
|
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++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.
|
|
|
|
Include <stddef.h> for offsetof. */
|
|
#include <stddef.h>
|
|
|
|
/* 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
|
|
|
|
/* 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))
|
|
# 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)
|
|
# endif
|
|
# else
|
|
# define _Alignof(type) offsetof (struct { char __a; type __b; }, __b)
|
|
# endif
|
|
#endif
|
|
#if ! (defined __cplusplus && 201103 <= __cplusplus)
|
|
# define alignof _Alignof
|
|
#endif
|
|
#define __alignof_is_defined 1
|
|
|
|
/* 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 ((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 _Alignas && ! (defined __cplusplus && 201103 <= __cplusplus)) \
|
|
|| (defined __STDC_VERSION__ && 201112 <= __STDC_VERSION__))
|
|
# define alignas _Alignas
|
|
#endif
|
|
#if defined alignas || (defined __cplusplus && 201103 <= __cplusplus)
|
|
# define __alignas_is_defined 1
|
|
#endif
|
|
|
|
#endif /* _GL_STDALIGN_H */
|