linux-kernel - [PATCH] checkpatch: Avoid multiple line dereferences

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Message-Id: <e9c191ae3f41bedc8ffd5c0fbcc5a1cec1d1d2df.1478120869.git.joe@perches.com>
Date:   Wed,  2 Nov 2016 14:25:13 -0700
From:   Joe Perches <joe@...ches.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Andy Whitcroft <apw@...onical.com>
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] checkpatch: Avoid multiple line dereferences

Code that puts a single dereferencing identifier on multiple lines like:

     struct_identifier->member[index].
	member = <foo>;

is generally hard to follow.

Prefer that dereferencing identifiers be single line.

Signed-off-by: Joe Perches <joe@...ches.com>
---
 scripts/checkpatch.pl | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index fdacd759078e..22abb4af5b4f 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3440,6 +3440,18 @@ sub process {
 #ignore lines not being added
 		next if ($line =~ /^[^\+]/);
 
+# check for dereferences that span multiple lines
+		if ($prevline =~ /^\+.*$Lval\s*(?:\.|->)\s*$/ &&
+		    $line =~ /^\+\s*(?!\#\s*(?!define\s+|if))\s*$Lval/) {
+			$prevline =~ /($Lval\s*(?:\.|->))\s*$/;
+			my $ref = $1;
+			$line =~ /^.\s*($Lval)/;
+			$ref .= $1;
+			$ref =~ s/\s//g;
+			WARN("MULTILINE_DEREFERENCE",
+			     "Avoid multiple line dereference - prefer '$ref'\n" . $hereprev);
+		}
+
 # check for declarations of signed or unsigned without int
 		while ($line =~ m{\b($Declare)\s*(?!char\b|short\b|int\b|long\b)\s*($Ident)?\s*[=,;\[\)\(]}g) {
 			my $type = $1;
-- 
2.10.0.rc2.1.g053435c