[PATCH] scripts: checkpatch.pl add warning for dummy label

[PATCH] scripts: checkpatch.pl add warning for dummy label

[Nitin Kuppelur]

Added new warning DUMMY_LABEL in checkpatch.pl. This warns
if return statement is encountered just after goto label target
like "out:". In such scenario it is best to call "return;" directly
instead of "goto out;"

Signed-off-by: Nitin Kuppelur <nitinkuppelur@gmail.com>
---
 scripts/checkpatch.pl | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index b602ed2..399c2b5 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3798,10 +3798,14 @@ sub process {
 		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" . $hereprev);
+		    $lines[$linenr - 3] =~ /^[ +]/) {
+			if ($lines[$linenr - 3] !~ /^[ +]\s*$Ident\s*:/) {
+				WARN("RETURN_VOID",
+				     "void function return statements are not generally useful\n" . $hereprev);
+			} elsif ($lines[$linenr - 3] =~ /^[ +]\s*$Ident\s*:/) {
+				WARN("DUMMY_LABEL",
+				     "labels doing nothing are not generally useful\n" . $hereprev);
+			}
                }
 
 # if statements using unnecessary parentheses - ie: if ((foo == bar))
-- 
1.9.1

Re: [PATCH] scripts: checkpatch.pl add warning for dummy label

[Joe Perches]

On Tue, 2014-09-09 at 15:54 +0200, Nitin Kuppelur wrote:
> Added new warning DUMMY_LABEL in checkpatch.pl. This warns
> if return statement is encountered just after goto label target
> like "out:". In such scenario it is best to call "return;" directly
> instead of "goto out;"

I'm not sure this is desired/correct.

There are many functions written like:

return_type foo(...)
{
	[some initialization...]

	err = some_test(...);
	if (err)
		goto out;

	[...]

out:
	[some cleanup...]
	return err;
}

In many cases, a void function is a simple
variant of a non-void function and many people
like to see the same code "shape" in functions,
just without the init and cleanup bits.

> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> @@ -3798,10 +3798,14 @@ sub process {
>  		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" . $hereprev);
> +		    $lines[$linenr - 3] =~ /^[ +]/) {
> +			if ($lines[$linenr - 3] !~ /^[ +]\s*$Ident\s*:/) {
> +				WARN("RETURN_VOID",
> +				     "void function return statements are not generally useful\n" . $hereprev);
> +			} elsif ($lines[$linenr - 3] =~ /^[ +]\s*$Ident\s*:/) {
> +				WARN("DUMMY_LABEL",
> +				     "labels doing nothing are not generally useful\n" . $hereprev);
> +			}
>                 }
>  
>  # if statements using unnecessary parentheses - ie: if ((foo == bar))

Re: [PATCH] scripts: checkpatch.pl add warning for dummy label

[Nitin Kuppelur]

Hi Joe,

Thanks for feedback.

The idea of adding new warning came from the review comments from
one of my PATCH, where it was suggested by few reviewers to remove such
"Do-Nothing" labels. But current checkpatch.pl does not warn about that.

[PATCH]
http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg720639.html


Regards,
Nitin

On 09/09/2014 05:43 PM, Joe Perches wrote:
> On Tue, 2014-09-09 at 15:54 +0200, Nitin Kuppelur wrote:
>> Added new warning DUMMY_LABEL in checkpatch.pl. This warns
>> if return statement is encountered just after goto label target
>> like "out:". In such scenario it is best to call "return;" directly
>> instead of "goto out;"
> 
> I'm not sure this is desired/correct.
> 
> There are many functions written like:
> 
> return_type foo(...)
> {
> 	[some initialization...]
> 
> 	err = some_test(...);
> 	if (err)
> 		goto out;
> 
> 	[...]
> 
> out:
> 	[some cleanup...]
> 	return err;
> }
> 
> In many cases, a void function is a simple
> variant of a non-void function and many people
> like to see the same code "shape" in functions,
> just without the init and cleanup bits.
> 
>> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> []
>> @@ -3798,10 +3798,14 @@ sub process {
>>  		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" . $hereprev);
>> +		    $lines[$linenr - 3] =~ /^[ +]/) {
>> +			if ($lines[$linenr - 3] !~ /^[ +]\s*$Ident\s*:/) {
>> +				WARN("RETURN_VOID",
>> +				     "void function return statements are not generally useful\n" . $hereprev);
>> +			} elsif ($lines[$linenr - 3] =~ /^[ +]\s*$Ident\s*:/) {
>> +				WARN("DUMMY_LABEL",
>> +				     "labels doing nothing are not generally useful\n" . $hereprev);
>> +			}
>>                 }
>>  
>>  # if statements using unnecessary parentheses - ie: if ((foo == bar))
> 
> 
>