On Mon, Aug 07, 2006 at 09:19:53PM +0200, Matthias Drochner
wrote:
>
> dyoung pobox.com said:
> > Per previous discussions, I am moving the
bit-twiddling macros [1] and
> > __arraycount from lib/libkern/libkern.h to
sys/cdefs.h
>
> Sorry, I missed that.
>
> > I have
> > added a __-prefix to SHIFTIN & SHIFTOUT
>
> What's the objective? I could imagine that you want to
use it in userlevel
> programs too, but then these would be highly
unportable. So an extra
> header and names without "__" prefix would
be more reasonable.
I want them in userland for the convenience of programs for
control &
diagnostics of device drivers. Portability is not key.
> And: It seems to me that the u_int32_t limitation is
not technically
> necessary. One could probably use "unsigned
long" and get the longest
> integer directly usable by the platform. Drawback would
be that
> people with 64-bit platforms could write non-partable
code. Gain would
> be that the macros could be used more effectively on
64-bit.
> And: The "(__n) == 32)" should better be a
">=". ">=8*sizeof(long)"
> if you follow my suggestion above.
I have heard that criticism at least once before. I have
tried to make
the macros widthless. See attached.
Dave
--
David Young OJC Technologies
dyoungojctech.com Urbana, IL * (217) 278-3933
/* $NetBSD: cdefs.h,v 1.60 2005/12/11 12:25:20 christos Exp
$ */
/*
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights
reserved.
*
* This code is derived from software contributed to
Berkeley by
* Berkeley Software Design, Inc.
*
* 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.
* 3. Neither the name of the University nor the names of
its contributors
* may be used to endorse or promote products derived
from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
*
* (#)cdefs.h 8.8 (Berkeley) 1/9/95
*/
#ifndef _SYS_CDEFS_H_
#define _SYS_CDEFS_H_
/*
* Macro to test if we're using a GNU C compiler of a
specific vintage
* or later, for e.g. features that appeared in a particular
version
* of GNU C. Usage:
*
* #if __GNUC_PREREQ__(major, minor)
* ...cool feature...
* #else
* ...delete feature...
* #endif
*/
#ifdef __GNUC__
#define __GNUC_PREREQ__(x, y) \
((__GNUC__ == (x) && __GNUC_MINOR__ >= (y))
|| \
(__GNUC__ > (x)))
#else
#define __GNUC_PREREQ__(x, y) 0
#endif
#include <machine/cdefs.h>
#ifdef __ELF__
#include <sys/cdefs_elf.h>
#else
#include <sys/cdefs_aout.h>
#endif
#if defined(__cplusplus)
#define __BEGIN_DECLS extern "C" {
#define __END_DECLS }
#define __static_cast(x,y) static_cast<x>(y)
#else
#define __BEGIN_DECLS
#define __END_DECLS
#define __static_cast(x,y) (x)y
#endif
/*
* The __CONCAT macro is used to concatenate parts of symbol
names, e.g.
* with "#define OLD(foo) __CONCAT(old,foo)",
OLD(foo) produces oldfoo.
* The __CONCAT macro is a bit tricky -- make sure you
don't put spaces
* in between its arguments. __CONCAT can also concatenate
double-quoted
* strings produced by the __STRING macro, but this only
works with ANSI C.
*/
#define ___STRING(x) __STRING(x)
#define ___CONCAT(x,y) __CONCAT(x,y)
#if __STDC__ || defined(__cplusplus)
#define __P(protos) protos /* full-blown ANSI C */
#define __CONCAT(x,y) x ## y
#define __STRING(x) #x
#define __const const /* define reserved names to standard
*/
#define __signed signed
#define __volatile volatile
#if defined(__cplusplus)
#define __inline inline /* convert to C++ keyword */
#else
#if !defined(__GNUC__) && !defined(__lint__)
#define __inline /* delete GCC keyword */
#endif /* !__GNUC__ && !__lint__ */
#endif /* !__cplusplus */
#else /* !(__STDC__ || __cplusplus) */
#define __P(protos) () /* traditional C preprocessor */
#define __CONCAT(x,y) x/**/y
#define __STRING(x) "x"
#ifndef __GNUC__
#define __const /* delete pseudo-ANSI C keywords */
#define __inline
#define __signed
#define __volatile
#endif /* !__GNUC__ */
/*
* In non-ANSI C environments, new programs will want
ANSI-only C keywords
* deleted from the program and old programs will want them
left alone.
* Programs using the ANSI C keywords const, inline etc. as
normal
* identifiers should define -DNO_ANSI_KEYWORDS.
*/
#ifndef NO_ANSI_KEYWORDS
#define const __const /* convert ANSI C keywords */
#define inline __inline
#define signed __signed
#define volatile __volatile
#endif /* !NO_ANSI_KEYWORDS */
#endif /* !(__STDC__ || __cplusplus) */
/*
* Used for internal auditing of the NetBSD source tree.
*/
#ifdef __AUDIT__
#define __aconst __const
#else
#define __aconst
#endif
/*
* The following macro is used to remove const cast-away
warnings
* from gcc -Wcast-qual; it should be used with caution
because it
* can hide valid errors; in particular most valid uses are
in
* situations where the API requires it, not to cast away
string
* constants. We don't use *intptr_t on purpose here and we
are
* explicit about unsigned long so that we don't have
additional
* dependencies.
*/
#define __UNCONST(a) ((void *)(unsigned long)(const void
*)(a))
/*
* The following macro is used to remove the volatile
cast-away warnings
* from gcc -Wcast-qual; as above it should be used with
caution
* because it can hide valid errors or warnings. Valid uses
include
* making it possible to pass a volatile pointer to
memset().
* For the same reasons as above, we use unsigned long and
not intptr_t.
*/
#define __UNVOLATILE(a) ((void *)(unsigned long)(volatile
void *)(a))
/*
* GCC2 provides __extension__ to suppress warnings for
various GNU C
* language extensions under "-ansi -pedantic".
*/
#if !__GNUC_PREREQ__(2, 0)
#define __extension__ /* delete __extension__ if non-gcc or
gcc1 */
#endif
/*
* GCC1 and some versions of GCC2 declare dead
(non-returning) and
* pure (no side effects) functions using
"volatile" and "const";
* unfortunately, these then cause warnings under
"-ansi -pedantic".
* GCC2 uses a new, peculiar __attribute__((attrs)) style.
All of
* these work for GNU C++ (modulo a slight glitch in the C++
grammar
* in the distribution version of 2.5.5).
*/
#if !__GNUC_PREREQ__(2, 5)
#define __attribute__(x) /* delete __attribute__ if non-gcc
or gcc1 */
#if defined(__GNUC__) && !defined(__STRICT_ANSI__)
#define __dead __volatile
#define __pure __const
#endif
#endif
/* Delete pseudo-keywords wherever they are not available or
needed. */
#ifndef __dead
#define __dead
#define __pure
#endif
#if __GNUC_PREREQ__(2, 7)
#define __unused __attribute__((__unused__))
#else
#define __unused /* delete */
#endif
#if __GNUC_PREREQ__(3, 1)
#define __used __attribute__((__used__))
#else
#define __used /* delete */
#endif
#if __GNUC_PREREQ__(2, 7)
#define __packed __attribute__((__packed__))
#define __aligned(x) __attribute__((__aligned__(x)))
#define __section(x) __attribute__((__section__(x)))
#elif defined(__lint__)
#define __packed /* delete */
#define __aligned(x) /* delete */
#define __section(x) /* delete */
#else
#define __packed error: no __packed for this compiler
#define __aligned(x) error: no __aligned for this compiler
#define __section(x) error: no __section for this compiler
#endif
/*
* C99 defines the restrict type qualifier keyword, which
was made available
* in GCC 2.92.
*/
#if __STDC_VERSION__ >= 199901L
#define __restrict restrict
#else
#if !__GNUC_PREREQ__(2, 92)
#define __restrict /* delete __restrict when not supported
*/
#endif
#endif
/*
* C99 defines __func__ predefined identifier, which was
made available
* in GCC 2.95.
*/
#if !(__STDC_VERSION__ >= 199901L)
#if __GNUC_PREREQ__(2, 6)
#define __func__ __PRETTY_FUNCTION__
#elif __GNUC_PREREQ__(2, 4)
#define __func__ __FUNCTION__
#else
#define __func__ ""
#endif
#endif /* !(__STDC_VERSION__ >= 199901L) */
#if defined(_KERNEL)
#if defined(NO_KERNEL_RCSIDS)
#undef __KERNEL_RCSID
#define __KERNEL_RCSID(_n, _s) /* nothing */
#endif /* NO_KERNEL_RCSIDS */
#endif /* _KERNEL */
#if !defined(_STANDALONE) && !defined(_KERNEL)
#ifdef __GNUC__
#define __RENAME(x) ___RENAME(x)
#else
#ifdef __lint__
#define __RENAME(x) __symbolrename(x)
#else
#error "No function renaming possible"
#endif /* __lint__ */
#endif /* __GNUC__ */
#else /* _STANDALONE || _KERNEL */
#define __RENAME(x) no renaming in kernel or standalone
environment
#endif
/*
* A barrier to stop the optimizer from moving code or
assume live
* register values. This is gcc specific, the version is
more or less
* arbitrary, might work with older compilers.
*/
#if __GNUC_PREREQ__(2, 95)
#define __insn_barrier() __asm
__volatile("":::"memory")
#else
#define __insn_barrier() /* */
#endif
/*
* GNU C version 2.96 adds explicit branch prediction so
that
* the CPU back-end can hint the processor and also so that
* code blocks can be reordered such that the predicted path
* sees a more linear flow, thus improving cache behavior,
etc.
*
* The following two macros provide us with a way to use
this
* compiler feature. Use __predict_true() if you expect the
expression
* to evaluate to true, and __predict_false() if you expect
the
* expression to evaluate to false.
*
* A few notes about usage:
*
* * Generally, __predict_false() error condition checks
(unless
* you have some _strong_ reason to do otherwise, in which
case
* document it), and/or __predict_true() `no-error'
condition
* checks, assuming you want to optimize for the no-error
case.
*
* * Other than that, if you don't know the likelihood of a
test
* succeeding from empirical or other `hard' evidence,
don't
* make predictions.
*
* * These are meant to be used in places that are run `a
lot'.
* It is wasteful to make predictions in code that is run
* seldomly (e.g. at subsystem initialization time) as the
* basic block reordering that this affects can often
generate
* larger code.
*/
#if __GNUC_PREREQ__(2, 96)
#define __predict_true(exp) __builtin_expect((exp) != 0, 1)
#define __predict_false(exp) __builtin_expect((exp) != 0, 0)
#else
#define __predict_true(exp) (exp)
#define __predict_false(exp) (exp)
#endif
/*
* Macros for manipulating "link sets". Link
sets are arrays of pointers
* to objects, which are gathered up by the linker.
*
* Object format-specific code has provided us with the
following macros:
*
* __link_set_add_text(set, sym)
* Add a reference to the .text symbol `sym' to `set'.
*
* __link_set_add_rodata(set, sym)
* Add a reference to the .rodata symbol `sym' to `set'.
*
* __link_set_add_data(set, sym)
* Add a reference to the .data symbol `sym' to `set'.
*
* __link_set_add_bss(set, sym)
* Add a reference to the .bss symbol `sym' to `set'.
*
* __link_set_decl(set, ptype)
* Provide an extern declaration of the set `set', which
* contains an array of the pointer type `ptype'. This
* macro must be used by any code which wishes to reference
* the elements of a link set.
*
* __link_set_start(set)
* This points to the first slot in the link set.
*
* __link_set_end(set)
* This points to the (non-existent) slot after the last
* entry in the link set.
*
* __link_set_count(set)
* Count the number of entries in link set `set'.
*
* In addition, we provide the following macros for
accessing link sets:
*
* __link_set_foreach(pvar, set)
* Iterate over the link set `set'. Because a link set is
* an array of pointers, pvar must be declared as
"type **pvar",
* and the actual entry accessed as "*pvar".
*
* __link_set_entry(set, idx)
* Access the link set entry at index `idx' from set
`set'.
*/
#define __link_set_foreach(pvar, set) \
for (pvar = __link_set_start(set); pvar <
__link_set_end(set); pvar++)
#define __link_set_entry(set,
idx) (__link_set_begin(set)[idx])
/*
* Return the number of elements in a statically-allocated
array,
* __x.
*/
#define __arraycount(__x) (sizeof(__x) / sizeof(__x[0]))
/* __BIT(n): nth bit, where __BIT(0) == 0x1. */
#define __BIT(__n) \
(((__n) >= NBBY * sizeof(uintmax_t)) ? 0 : ((uintmax_t)1
<< (__n)))
/* __BITS(m, n): bits m through n, m < n. */
#define __BITS(__m, __n) \
((__BIT(MAX((__m), (__n)) + 1) - 1) ^ (__BIT(MIN((__m),
(__n))) - 1))
/* find least significant bit that is set */
#define __LOWEST_SET_BIT(__mask) ((((__mask) - 1) &
(__mask)) ^ (__mask))
#define __PRIxBIT PRIxMAX
#define __PRIxBITS __PRIxBIT
#define __SHIFTOUT(__x, __mask) \
((typeof(__x))(((__x) & (__mask)) /
__LOWEST_SET_BIT(__mask)))
#define __SHIFTIN(__x, __mask) ((typeof(__x))((__x) *
__LOWEST_SET_BIT(__mask)))
#define __SHIFTOUT_MASK(__mask) __SHIFTOUT((__mask),
(__mask))
#endif /* !_SYS_CDEFS_H_ */
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