[src/trunk]: src Document the alignof GNU extension.

To: source-changes-hg%NetBSD.org@localhost
Subject: [src/trunk]: src Document the __alignof__ GNU extension.
From: jruoho <jruoho%NetBSD.org@localhost>
Date: Mon, 06 Apr 2020 19:40:02 +0000
details:   https://anonhg.NetBSD.org/src/rev/ebcf4f0abe83
branches:  trunk
changeset: 759877:ebcf4f0abe83
user:      jruoho <jruoho%NetBSD.org@localhost>
date:      Sun Dec 19 08:10:07 2010 +0000

description:
Document the __alignof__ GNU extension.

diffstat:

 distrib/sets/lists/comp/mi   |   5 ++-
 share/man/man3/Makefile      |   4 +-
 share/man/man3/__alignof__.3 |  84 ++++++++++++++++++++++++++++++++++++++++++++
 share/man/man3/attribute.3   |   7 ++-
 share/man/man3/offsetof.3    |   8 ++-
 share/man/man3/typeof.3      |   5 +-
 6 files changed, 103 insertions(+), 10 deletions(-)

diffs (218 lines):

diff -r c5a4060478f1 -r ebcf4f0abe83 distrib/sets/lists/comp/mi
--- a/distrib/sets/lists/comp/mi        Sat Dec 18 23:36:23 2010 +0000
+++ b/distrib/sets/lists/comp/mi        Sun Dec 19 08:10:07 2010 +0000
@@ -1,4 +1,4 @@
-#      $NetBSD: mi,v 1.1554 2010/12/17 12:14:03 jruoho Exp $
+#      $NetBSD: mi,v 1.1555 2010/12/19 08:10:07 jruoho Exp $
 #
 # Note: don't delete entries from here - mark them as "obsolete" instead.
 #
@@ -4906,6 +4906,7 @@
 ./usr/share/man/cat3/__UNCONST.0               comp-c-catman           .cat
 ./usr/share/man/cat3/__UNVOLATILE.0            comp-c-catman           .cat
 ./usr/share/man/cat3/__aligned.0               comp-c-catman           .cat
+./usr/share/man/cat3/__alignof__.0             comp-c-catman           .cat
 ./usr/share/man/cat3/__arraycount.0            comp-c-catman           .cat
 ./usr/share/man/cat3/__builtin_object_size.0   comp-c-catman           .cat
 ./usr/share/man/cat3/__cacheline_aligned.0     comp-c-catman           .cat
@@ -10994,6 +10995,7 @@
 ./usr/share/man/html3/__UNCONST.html           comp-c-htmlman          html
 ./usr/share/man/html3/__UNVOLATILE.html                comp-c-htmlman          html
 ./usr/share/man/html3/__aligned.html           comp-c-htmlman          html
+./usr/share/man/html3/__alignof__.html         comp-c-htmlman          html
 ./usr/share/man/html3/__arraycount.html                comp-c-htmlman          html
 ./usr/share/man/html3/__builtin_object_size.html       comp-c-htmlman          html
 ./usr/share/man/html3/__cacheline_aligned.html comp-c-htmlman          html
@@ -16882,6 +16884,7 @@
 ./usr/share/man/man3/__UNCONST.3               comp-c-man              .man
 ./usr/share/man/man3/__UNVOLATILE.3            comp-c-man              .man
 ./usr/share/man/man3/__aligned.3               comp-c-man              .man
+./usr/share/man/man3/__alignof__.3             comp-c-man              .man
 ./usr/share/man/man3/__arraycount.3            comp-c-man              .man
 ./usr/share/man/man3/__builtin_object_size.3   comp-c-man              .man
 ./usr/share/man/man3/__cacheline_aligned.3     comp-c-man              .man
diff -r c5a4060478f1 -r ebcf4f0abe83 share/man/man3/Makefile
--- a/share/man/man3/Makefile   Sat Dec 18 23:36:23 2010 +0000
+++ b/share/man/man3/Makefile   Sun Dec 19 08:10:07 2010 +0000
@@ -1,8 +1,8 @@
-#      $NetBSD: Makefile,v 1.64 2010/12/17 12:14:04 jruoho Exp $
+#      $NetBSD: Makefile,v 1.65 2010/12/19 08:10:08 jruoho Exp $
 #      @(#)Makefile    8.2 (Berkeley) 12/13/93
 
 MAN=   _DIAGASSERT.3 __CONCAT.3 __UNCONST.3 CMSG_DATA.3 \
-       __arraycount.3 __insn_barrier.3 \
+       __alignof__.3 __arraycount.3 __insn_barrier.3 \
        assert.3 attribute.3 bits.3 bitstring.3 \
        cdefs.3 dirent.3 dlfcn.3 dl_iterate_phdr.3 end.3 \
        fast_divide32.3 ffs32.3 gcq.3 \
diff -r c5a4060478f1 -r ebcf4f0abe83 share/man/man3/__alignof__.3
--- /dev/null   Thu Jan 01 00:00:00 1970 +0000
+++ b/share/man/man3/__alignof__.3      Sun Dec 19 08:10:07 2010 +0000
@@ -0,0 +1,84 @@
+.\" $NetBSD: __alignof__.3,v 1.1 2010/12/19 08:10:09 jruoho Exp $
+.\"
+.\" Copyright (c) 2010 Jukka Ruohonen <jruohonen%iki.fi@localhost>
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+.\" PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+.\" POSSIBILITY OF SUCH DAMAGE.
+.\"
+.Dd December 19, 2010
+.Dt __alignof__ 3
+.Os
+.Sh NAME
+.Nm __alignof__
+.Nd GNU extension for alignment of an object
+.Sh SYNOPSIS
+.Ft int
+.Fn __alignof__ "void type"
+.Sh DESCRIPTION
+The
+.Fn __alignof__
+operator returns the alignment of its operand.
+The operand can be a type or an expression.
+If the operand is a
+.Sq lvalue ,
+the return value represents the required alignment of the underlying type,
+not the actual alignment of the specified
+.Sq lvalue .
+.Pp
+The returned value is specific to the architecture and the
+.Tn ABI .
+If the architecture does not impose strict alignment requirements,
+.Fn __alignof__
+returns the minimum required alignment.
+If
+.Xr __aligned 3
+is used to increase the alignment,
+.Fn __alignof__
+returns the specified alignment.
+.Sh EXAMPLES
+The syntax is comparable to the
+.Fn sizeof
+operator.
+If the architecture aligns integers along 32-bit address boundaries,
+the following should print the value 4.
+.Bd -literal -offset indent
+(void)printf(\*[q]%d\\n\*[q], __alignof__(int));
+.Ed
+.Pp
+On the other hand, the following example probably prints the value 1,
+even though this is unlikely to be the actual alignment of the
+structure member.
+.Bd -literal -offset indent
+struct align {
+       int  x;
+       char y;
+} a;
+
+(void)printf(\*[q]%d\\n\*[q], __alignof__(a.y));
+.Ed
+.Sh SEE ALSO
+.Xr gcc 1 ,
+.Xr attribute 3 ,
+.Xr offsetof 3 ,
+.Xr typeof 3
+.Sh CAVEATS
+This is a non-standard, compiler-specific extension.
diff -r c5a4060478f1 -r ebcf4f0abe83 share/man/man3/attribute.3
--- a/share/man/man3/attribute.3        Sat Dec 18 23:36:23 2010 +0000
+++ b/share/man/man3/attribute.3        Sun Dec 19 08:10:07 2010 +0000
@@ -1,4 +1,4 @@
-.\" $NetBSD: attribute.3,v 1.8 2010/12/17 08:23:04 jruoho Exp $
+.\" $NetBSD: attribute.3,v 1.9 2010/12/19 08:10:09 jruoho Exp $
 .\"
 .\" Copyright (c) 2010 The NetBSD Foundation, Inc.
 .\" All rights reserved.
@@ -27,7 +27,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd December 16, 2010
+.Dd December 19, 2010
 .Dt ATTRIBUTE 3
 .Os
 .Sh NAME
@@ -208,6 +208,9 @@
 The effectiveness of
 .Fn __aligned
 is largely dependent on the linker.
+The
+.Xr __alignof__ 3
+operator can be used to examine the alignment.
 .It Fn __section "section"
 The
 .Fn __section
diff -r c5a4060478f1 -r ebcf4f0abe83 share/man/man3/offsetof.3
--- a/share/man/man3/offsetof.3 Sat Dec 18 23:36:23 2010 +0000
+++ b/share/man/man3/offsetof.3 Sun Dec 19 08:10:07 2010 +0000
@@ -1,4 +1,4 @@
-.\"    $NetBSD: offsetof.3,v 1.2 2010/03/21 12:36:21 jruoho Exp $
+.\"    $NetBSD: offsetof.3,v 1.3 2010/12/19 08:10:09 jruoho Exp $
 .\"
 .\"    $OpenBSD: offsetof.3,v 1.2 2010/02/18 18:30:19 jmc Exp $
 .\"
@@ -17,7 +17,7 @@
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
 .\"
-.Dd February 18, 2010
+.Dd December 19, 2010
 .Dt OFFSETOF 3
 .Os
 .Sh NAME
@@ -42,7 +42,9 @@
 .Ar member
 is not aligned to a byte boundary (i.e. it is a bit-field).
 .Sh SEE ALSO
-.Xr stddef 3
+.Xr __alignof__ 3 ,
+.Xr stddef 3 ,
+.Xr typeof 3
 .Sh STANDARDS
 The
 .Fn offsetof
diff -r c5a4060478f1 -r ebcf4f0abe83 share/man/man3/typeof.3
--- a/share/man/man3/typeof.3   Sat Dec 18 23:36:23 2010 +0000
+++ b/share/man/man3/typeof.3   Sun Dec 19 08:10:07 2010 +0000
@@ -1,4 +1,4 @@
-.\" $NetBSD: typeof.3,v 1.1 2010/12/17 12:14:04 jruoho Exp $
+.\" $NetBSD: typeof.3,v 1.2 2010/12/19 08:10:09 jruoho Exp $
 .\"
 .\" Copyright (c) 2010 Jukka Ruohonen <jruohonen%iki.fi@localhost>
 .\" All rights reserved.
@@ -24,7 +24,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd December 17, 2010
+.Dd December 19, 2010
 .Dt TYPEOF 3
 .Os
 .Sh NAME
@@ -54,6 +54,7 @@
 .Ed
 .Sh SEE ALSO
 .Xr gcc 1 ,
+.Xr __alignof__ 3 ,
 .Xr attribute 3 ,
 .Xr offsetof 3
 .Sh CAVEATS
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[src/trunk]: src Document the __alignof__ GNU extension.

[src/trunk]: src Document the alignof GNU extension.
