Date: Fri, 27 Dec 2002 11:50:40 -0800 From: Jeffrey Hsu <hsu@FreeBSD.org> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG Subject: Re: cvs commit: src/sys/kern uipc_usrreq.c Message-ID: <0H7S0085YN2VDE@mta6.snfc21.pbi.net> In-Reply-To: Message from Matthew Dillon <dillon@apollo.backplane.com> "of Fri, 27 Dec 2002 10:55:44 PST." <200212271855.gBRItiIC057945@apollo.backplane.com>
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> It will work
Yes, let's not forget this. The old code didn't work. And, the
question that was initially asked a basic C sequence point question
on whether the ternary operator worked with the pre-increment operator.
> there really is no reason
> to collapse the mess onto a single line
I can think of three reasons:
1. Precedent
See netinet/tcp_seq.h:
/* Macro to increment a CC: skip 0 which has a special meaning */
#define CC_INC(c) (++(c) == 0 ? ++(c) : (c))
2. Readability
Compare the committed version
if (unp->unp_ino == 0)
unp->unp_ino = (++unp_ino == 0) ? ++unp_ino : unp_ino;
sb->st_ino = unp->unp_ino;
with the broken out version
if (unp->unp_ino == 0)
if (++unp_ino == 0)
unp->unp_ino = ++unp_ino;
else
unp->unp_ino = unp_ino;
sb->st_ino = unp->unp_ino;
The second version obscures the assignment inside the control flow.
The similarity of the unp->unp_ino and unp_ino names makes
it hard for the naked eye to follow the multiple occurrences of
unp->unp_ino and unp_ino.
The committed version makes it clear the assignment to unp->unp_ino
is the primary intent of the body of the conditional.
3. Brevity
The committed version is shorter.
Jeffrey
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