linux-kernel - Re: [PATCH V2] checkpatch: Warn on unnecessary void function return statements

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Message-Id: <20140619131837.b13ab73f682469ff852cee49@linux-foundation.org>
Date:	Thu, 19 Jun 2014 13:18:37 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Joe Perches <joe@...ches.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Anish Bhatt <anish@...lsio.com>
Subject: Re: [PATCH V2] checkpatch: Warn on unnecessary void function return
 statements

On Wed, 18 Jun 2014 10:44:44 -0700 Joe Perches <joe@...ches.com> wrote:

> With some exceptions, warn on void functions that end with a
> "return;", because it's unnecessary.
> 
> Check the closing brace at the start of a line.
> If the line before that has a single tab, then return;
> look at the line before that.  If it's not a label,
> emit a warning.
> 
> So, emit a warning on:
> 
> void function(...)
> {
> 	[...]
> 	return;
> }
> 
> but do not emit a warning on the below because
> gcc requires any statement (including a bare
> semicolon) before the closing function brace:
> 
> void function(...)
> {
> 	[...]
> 		goto label;
> 	[...]
> 
> label:
> 	return;
> }
> 
> Signed-off-by: Joe Perches <joe@...ches.com>
> ---
> 
> V2: The previous patch had a few too many false positives
>     on styles that should be acceptable.

Previous patch is now in mainline, so I did this:


From: Joe Perches <joe@...ches.com>
Subject: checkpatch: reduce false positives when checking void function return statements

The previous patch had a few too many false positives on styles that
should be acceptable.

Signed-off-by: Joe Perches <joe@...ches.com>
Tested-by: Anish Bhatt <anish@...lsio.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 scripts/checkpatch.pl |   15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff -puN scripts/checkpatch.pl~checkpatch-reduce-false-positives-when-checking-void-function-return-statements scripts/checkpatch.pl
--- a/scripts/checkpatch.pl~checkpatch-reduce-false-positives-when-checking-void-function-return-statements
+++ a/scripts/checkpatch.pl
@@ -3484,12 +3484,17 @@ sub process {
 			}
 		}
 
-# unnecessary return in a void function? (a single leading tab, then return;)
-		if ($sline =~ /^\+\treturn\s*;\s*$/ &&
-		    $prevline =~ /^\+/) {
+# unnecessary return in a void function
+# at end-of-function, with the previous line a single leading tab, then return;
+# and the line before that not a goto label target like "out:"
+		if ($sline =~ /^[ \+]}\s*$/ &&
+		    $prevline =~ /^\+\treturn\s*;\s*$/ &&
+		    $linenr >= 3 &&
+		    $lines[$linenr - 3] =~ /^[ +]/ &&
+		    $lines[$linenr - 3] !~ /^[ +]\s*$Ident\s*:/) {
 			WARN("RETURN_VOID",
-			     "void function return statements are not generally useful\n" . $herecurr);
-		}
+			     "void function return statements are not generally useful\n" . $hereprev);
+               }
 
 # if statements using unnecessary parentheses - ie: if ((foo == bar))
 		if ($^V && $^V ge 5.10.0 &&
_

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