From 34a8e7368f3f00d4564b0b980871f73929d6b1ce Mon Sep 17 00:00:00 2001
From: Warner Losh <imp@FreeBSD.org>
Date: Thu, 16 Jul 2020 14:12:54 +0000
Subject: [PATCH] Relax the rule against declaring variables in nested scopes
 and for initializations.

Relax some overly perscriptive rules against declarations: they may be at the
start of any blocks, even if things aren't super complicated. Allow more
initializations (those that call simple functions, like accessor functions for
newbus are fine). Allow the common idiom of declaring the loop variable in a for
loop.

This tries to codify what common exceptions are today, as well as give
some guidance on when it's best to do these things.

Reviewed by: tsoome, kp, markm, allanjude, jiles, cem, rpokala
	(earlier versions: seanc, melifaro, bapt, pjd, bz, pstef, arichards,
	 jhibits, vangyzen, jmallet, ian, glebius, jhb, dab, adrian,
	 sef, gnn)
Differential Revision: https://reviews.freebsd.org/D25312
---
 share/man/man9/style.9 | 34 +++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/share/man/man9/style.9 b/share/man/man9/style.9
index 0798de793b51..08f874635b23 100644
--- a/share/man/man9/style.9
+++ b/share/man/man9/style.9
@@ -25,7 +25,7 @@
 .\"	From: @(#)style	1.14 (Berkeley) 4/28/95
 .\" $FreeBSD$
 .\"
-.Dd June 30, 2020
+.Dd July 16, 2020
 .Dt STYLE 9
 .Os
 .Sh NAME
@@ -592,8 +592,6 @@ not
 Parts of a
 .Ic for
 loop may be left empty.
-Do not put declarations
-inside blocks unless the routine is unusually complicated.
 .Bd -literal
 	for (; cnt < 15; cnt++) {
 		stmt1;
@@ -601,6 +599,15 @@ inside blocks unless the routine is unusually complicated.
 	}
 .Ed
 .Pp
+A
+.Ic for
+loop may declare and initialize its counting variable.
+.Bd -literal
+	for (int i = 0; i < 15; i++) {
+		stmt1;
+	}
+.Ed
+.Pp
 Indentation is an 8 character tab.
 Second level indents are four spaces.
 If you have to wrap a long statement, put the operator at the end of the
@@ -676,25 +683,26 @@ The opening brace of the function body should be
 on a line by itself.
 .Bd -literal
 static char *
-function(int a1, int a2, float fl, int a4)
+function(int a1, int a2, float fl, int a4, struct bar *bar)
 {
 .Ed
 .Pp
 When declaring variables in functions declare them sorted by size,
 then in alphabetical order; multiple ones per line are okay.
 If a line overflows reuse the type keyword.
-.Pp
-Be careful to not obfuscate the code by initializing variables in
-the declarations.
-Use this feature only thoughtfully.
-DO NOT use function calls in initializers.
+Variables may be initialized where declared especially when they
+are constant for the rest of the scope.
+Declarations may be placed before executable lines at the start
+of any block.
+Calls to complicated functions should be avoided when initializing variables.
 .Bd -literal
 	struct foo one, *two;
-	double three;
-	int *four, five;
-	char *six, seven, eight, nine, ten, eleven, twelve;
+	struct baz *three = bar_get_baz(bar);
+	double four;
+	int *five, six;
+	char *seven, eight, nine, ten, eleven, twelve;
 
-	four = myfunction();
+	four = my_complicated_function(a1, f1, a4);
 .Ed
 .Pp
 Do not declare functions inside other functions; ANSI C says that