Module Name: src
Committed By: jruoho
Date: Sun Dec 19 10:07:24 UTC 2010
Modified Files:
src/distrib/sets/lists/comp: mi
src/share/man/man3: Makefile
Added Files:
src/share/man/man3: __builtin_constant_p.3
Log Message:
Document __builtin_constant_p().
To generate a diff of this commit:
cvs rdiff -u -r1.1556 -r1.1557 src/distrib/sets/lists/comp/mi
cvs rdiff -u -r1.66 -r1.67 src/share/man/man3/Makefile
cvs rdiff -u -r0 -r1.1 src/share/man/man3/__builtin_constant_p.3
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/distrib/sets/lists/comp/mi
diff -u src/distrib/sets/lists/comp/mi:1.1556 src/distrib/sets/lists/comp/mi:1.1557
--- src/distrib/sets/lists/comp/mi:1.1556 Sun Dec 19 09:30:49 2010
+++ src/distrib/sets/lists/comp/mi Sun Dec 19 10:07:23 2010
@@ -1,4 +1,4 @@
-# $NetBSD: mi,v 1.1556 2010/12/19 09:30:49 jruoho Exp $
+# $NetBSD: mi,v 1.1557 2010/12/19 10:07:23 jruoho Exp $
#
# Note: don't delete entries from here - mark them as "obsolete" instead.
#
@@ -4908,6 +4908,7 @@
./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_constant_p.0 comp-c-catman .cat
./usr/share/man/cat3/__builtin_frame_address.0 comp-c-catman .cat
./usr/share/man/cat3/__builtin_object_size.0 comp-c-catman .cat
./usr/share/man/cat3/__builtin_return_address.0 comp-c-catman .cat
@@ -10999,6 +11000,7 @@
./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_constant_p.html comp-c-htmlman html
./usr/share/man/html3/__builtin_frame_address.html comp-c-htmlman html
./usr/share/man/html3/__builtin_object_size.html comp-c-htmlman html
./usr/share/man/html3/__builtin_return_address.html comp-c-htmlman html
@@ -16890,6 +16892,7 @@
./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_constant_p.3 comp-c-man .man
./usr/share/man/man3/__builtin_frame_address.3 comp-c-man .man
./usr/share/man/man3/__builtin_object_size.3 comp-c-man .man
./usr/share/man/man3/__builtin_return_address.3 comp-c-man .man
Index: src/share/man/man3/Makefile
diff -u src/share/man/man3/Makefile:1.66 src/share/man/man3/Makefile:1.67
--- src/share/man/man3/Makefile:1.66 Sun Dec 19 09:30:50 2010
+++ src/share/man/man3/Makefile Sun Dec 19 10:07:24 2010
@@ -1,9 +1,9 @@
-# $NetBSD: Makefile,v 1.66 2010/12/19 09:30:50 jruoho Exp $
+# $NetBSD: Makefile,v 1.67 2010/12/19 10:07:24 jruoho Exp $
# @(#)Makefile 8.2 (Berkeley) 12/13/93
MAN= _DIAGASSERT.3 __CONCAT.3 __UNCONST.3 CMSG_DATA.3 \
__alignof__.3 __arraycount.3 \
- __builtin_return_address.3 __insn_barrier.3 \
+ __builtin_constant_p.3 __builtin_return_address.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 \
Added files:
Index: src/share/man/man3/__builtin_constant_p.3
diff -u /dev/null src/share/man/man3/__builtin_constant_p.3:1.1
--- /dev/null Sun Dec 19 10:07:24 2010
+++ src/share/man/man3/__builtin_constant_p.3 Sun Dec 19 10:07:24 2010
@@ -0,0 +1,78 @@
+.\" $NetBSD: __builtin_constant_p.3,v 1.1 2010/12/19 10:07:24 jruoho Exp $
+.\"
+.\" Copyright (c) 2010 Jukka Ruohonen <jruoho...@iki.fi>
+.\" 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 __BUILTIN_CONSTANT_P 3
+.Os
+.Sh NAME
+.Nm __builtin_constant_p
+.Nd GNU extension to determine compile time constants
+.Sh SYNOPSIS
+.Ft int
+.Fn __builtin_constant_p "value"
+.Sh DESCRIPTION
+The
+.Fn __builtin_constant_p
+is a
+.Tn GNU
+extension for determining whether a value
+is known to be constant at compile time.
+The function is closely related to the concept of
+.Dq constant folding
+used by modern optimizing compilers.
+.Pp
+If the
+.Fa value
+is known to be a compile-time constant, a value 1 is returned.
+If
+.Fn __builtin_constant_p
+returns 0, the
+.Fa value
+is not a compile-time constant in the sense that
+.Xr gcc 1
+was unable to determine whether the value is constant or not.
+.Sh EXAMPLES
+A typical example of the use of
+.Fn __builtin_constant_p
+involves a situation where it may be desirable to
+fold the computation if it involves a constant,
+but a function call is needed otherwise.
+For instance,
+.Xr bswap 16
+is defined in
+.Nx
+as:
+.Bd -literal -offset indent
+#define bswap16(x) \\
+ (__builtin_constant_p((x)) ? \\
+ __byte_swap_u16_constant(x) : __BYTE_SWAP_U16_VARIABLE(x))
+.Ed
+.Sh SEE ALSO
+.Xr gcc 1 ,
+.Xr __builtin_object_size 3 ,
+.Xr __builtin_return_address 3
+.Sh CAVEATS
+This is a non-standard, compiler-specific extension.
