X-Git-Url: https://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Fstdalign.in.h;h=1523058134018d6b3296a603c5da3e63c0183689;hb=341111f654709cd0295607a4abbe721495c77e90;hp=092dfedae6606124d7cfd571fe029fb92de4708c;hpb=6dc2ffa573d23caeeb62c4ba3b9a630a1261e35d;p=gnulib.git

diff --git a/lib/stdalign.in.h b/lib/stdalign.in.h
index 092dfedae..152305813 100644
--- a/lib/stdalign.in.h
+++ b/lib/stdalign.in.h
@@ -1,6 +1,6 @@
-/* A substitute for ISO C 1x <stdalign.h>.
+/* A substitute for ISO C11 <stdalign.h>.
 
-   Copyright 2011 Free Software Foundation, Inc.
+   Copyright 2011-2012 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
@@ -13,30 +13,35 @@
    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>
 #if defined __cplusplus
    template <class __t> struct __alignof_helper { char __a; __t __b; };
@@ -47,11 +52,35 @@
 #define alignof _Alignof
 #define __alignof_is_defined 1
 
-/* Align a type or variable to the alignment A.  */
-#if @HAVE_ATTRIBUTE_ALIGNED@ && !defined __cplusplus
+/* 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 __GNUC__ || __IBMC__ || __IBMCPP__ || 0x5110 <= __SUNPRO_C
 # define _Alignas(a) __attribute__ ((__aligned__ (a)))
 #elif 1300 <= _MSC_VER
-# define _Alignas(a) __declspec ((align (a)))
+# define _Alignas(a) __declspec (align (a))
 #endif
 #ifdef _Alignas
 # define alignas _Alignas