Re: SET, CLR, ISSET in types.h for _KERNEL builds
- From: Bruce Evans <bde@xxxxxxxxxxx>
- Date: Wed, 28 Jun 2006 22:55:22 +1000 (EST)
On Wed, 28 Jun 2006, Poul-Henning Kamp wrote:
In message <20060628094221.GA50978@xxxxxxxxxxxxxxxx>, Yar Tikhiy writes:On Tue, Jun 27, 2006 at 01:58:17PM -0600, M. Warner Losh wrote:
NetBSD recently added SET, CLR, ISSET to sys/types.h (only if _KERNEL
is defined).
I see no types here.
As one of the people who have worked with the original /bin/sh source
code, I have a slight alergic reaction to attempts to paste over
the implementation language with macros like these.
Setting a bit in 'C' is spelled
variable |= bit;
not
SET(variable, bit);
Only slightly?
In FreeBSD, these mistakes were only in kern/tty.c and in some usb
files obtained from NetBSD and related to tty.c. In tty.c, they appear
to be just to avoid adding a USL copyright. (tty.c was obfuscated
between FreeBSD-1 and FreeBSD-2 by globally substituting "variable |=
BIT" by "SET(variable, BIT)", etc.) I noticed that NetBSD started
using these macros elsewhere many years ago. However, their use was
still relatively limited in NetBSD a year ago (in kern, they were only
in kern-fork.c (1), kern_subr.c (2), kern_systrace.c (many), sys_process.c
(a few), tty.c (many), tty_pty.c (many), vfs_bio.c (many) and vfs_lookup.c
(1); 211 lines altogether vs 1565 lines matching ' & ' and 27 lines
matching the style bug '[A-Za-z]&[A-Za-z]'). It must have been in
tty_pty.c that I noticed them many years ago.
Higher order macros like roundup(), ispow2() are fine with me,
because they implement something on top of the language and make
the source code more compact and thus faster to read.
But all of the three proposed macros take up more space than
the native language they obfuscate, what is the sense in that ?
They might be to hide the implementation of a set of flags as a bitmap,
but they don't even do that.
Another problem with these macros is that a bitmap is more useful than
a set of flags, but a much larger and uglier set of macros would be
needed to give enough operations on bitmaps, and code that has been
blindly translated from an integer-bitmap operation still assumes that
the implementation is an integer-bitmap. E.g., in tty.c:
%%%
/*
* delayed suspend (^Y)
*/
if (CCEQ(cc[VDSUSP], c) &&
ISSET(lflag, IEXTEN | ISIG) == (IEXTEN | ISIG)) {
%%%
Bruce
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- From: Poul-Henning Kamp
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