[src/trunk]: src/share/misc Clarify and explain the rationale for parentheses...

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/db7766cc4387
branches:  trunk
changeset: 960766:db7766cc4387
user:      christos <christos%NetBSD.org@localhost>
date:      Sun Mar 28 14:28:56 2021 +0000

description:
Clarify and explain the rationale for parentheses in sizeof and return as
discussed.

diffstat:

 share/misc/style |  28 ++++++++++++++++++++++------
 1 files changed, 22 insertions(+), 6 deletions(-)

diffs (49 lines):

diff -r b510b166fbfb -r db7766cc4387 share/misc/style
--- a/share/misc/style  Sun Mar 28 14:16:16 2021 +0000
+++ b/share/misc/style  Sun Mar 28 14:28:56 2021 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: style,v 1.61 2021/03/28 14:16:16 christos Exp $ */
+/* $NetBSD: style,v 1.62 2021/03/28 14:28:56 christos Exp $ */
 
 /*
  * The revision control tag appears first, with a blank line after it.
@@ -30,7 +30,7 @@
 #include <sys/cdefs.h>
 __COPYRIGHT("@(#) Copyright (c) 2008\
  The NetBSD Foundation, inc. All rights reserved.");
-__RCSID("$NetBSD: style,v 1.61 2021/03/28 14:16:16 christos Exp $");
+__RCSID("$NetBSD: style,v 1.62 2021/03/28 14:28:56 christos Exp $");
 
 /*
  * VERY important single-line comments look like this.
@@ -351,10 +351,26 @@
        char fourteen, fifteen, sixteen;
 
        /*
-        * Casts and sizeof's are not followed by a space.  NULL is any
-        * pointer type, and doesn't need to be cast, so use NULL instead
-        * of (struct foo *)0 or (struct foo *)NULL.  Also, test pointers
-        * against NULL.  I.e. use:
+        * Casts and sizeof's are not followed by a space.
+        *
+        * We parenthesize sizeof expressions to clarify their precedence:
+        *
+        *      sizeof(e) + 4
+        * not:
+        *      sizeof e + 4
+        *
+        * We don't put a space before the parenthesis so that it looks like
+        * a function call. We always parenthesize the sizeof expression for
+        * consistency.
+        *
+        * On the other hand, we don't parenthesize the return statement
+        * because there is never a precedence ambiguity situation (it is
+        * a single statement).
+        *
+        * NULL is any pointer type, and doesn't need to be cast, so use
+        * NULL instead of (struct foo *)0 or (struct foo *)NULL.  Also,
+        * test pointers against NULL because it indicates the type of the
+        * expression to the user. I.e. use:
         *
         *      (p = f()) == NULL
         * not: