Re: [PATCH] checkpatch: warn about hunks which only add blank lines

On 18/08/2026 11.29, Denis V. Lunev wrote:
> On 7/31/26 15:40, Denis V. Lunev wrote:
>> This email originated from an IP that might not be authorized by the domain it was sent from.
>> Do not click links or open attachments unless it is an email you expected to receive.
>> Patches sometimes carry a hunk whose entire content is one or two
>> added blank lines. It changes nothing, it makes the diff longer and
>> it survives review because nobody looks twice at a blank line. The
>> blank line itself is perfectly fine, the gratuitous hunk is not.
>>
>> Tally the added blank lines and the other changes of every hunk in
>> the pre-scan loop which already walks the raw patch, and record the
>> hunks which only add blanks. Such a hunk is then reported at the
>> first blank line it adds, so the warning carries the usual file and
>> line context.
>>
>> Signed-off-by: Denis V. Lunev <[email protected]>
>> CC: Chao Liu <[email protected]>
>> CC: "Daniel P. Berrange" <[email protected]>
>> CC: "Philippe Mathieu-Daude" <[email protected]>
>> CC: Thomas Huth <[email protected]>
>> ---
>> Note: this patch is sent on behalf of the yesterday finding inside IDE
>>        pull request. This should be found with a checkpatch.
>>
>>   scripts/checkpatch.pl | 21 +++++++++++++++++++++
>>   1 file changed, 21 insertions(+)
>>
>> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
>> index 03f35e7501..dfa9878006 100755
>> --- a/scripts/checkpatch.pl
>> +++ b/scripts/checkpatch.pl
>> @@ -1567,6 +1567,10 @@ sub process {
>>   	my $first_line = 0;
>>   	my $p1_prefix = '';
>>   
>> +	my %blank_only_hunk;
>> +	my $hunk_first_blank = 0;
>> +	my $hunk_has_change = 0;
>> +
>>   	my $prev_values = 'E';
>>   
>>   	# suppression flags
>> @@ -1583,6 +1587,10 @@ sub process {
>>   		$line = $rawline;
>>   
>>   		if ($rawline=~/^\@\@ -\d+(?:,\d+)? \+(\d+)(,(\d+))? \@\@/) {
>> +			$blank_only_hunk{$hunk_first_blank} = 1
>> +				if ($hunk_first_blank && !$hunk_has_change);
>> +			($hunk_first_blank, $hunk_has_change) = (0, 0);
>> +
>>   			$realline=$1-1;
>>   			if (defined $2) {
>>   				$realcnt=$3+1;
>> @@ -1633,6 +1641,13 @@ sub process {
>>   		push(@lines, $line);
>>   
>>   		if ($realcnt > 1) {
>> +			if ($rawline =~ /^\+\s*$/) {
>> +				$hunk_first_blank = $linenr
>> +					if (!$hunk_first_blank);
>> +			} elsif ($rawline =~ /^[-+]/) {
>> +				$hunk_has_change = 1;
>> +			}
>> +
>>   			$realcnt-- if ($line =~ /^(?:\+| |$)/);
>>   		} else {
>>   			$realcnt = 0;
>> @@ -1641,6 +1656,8 @@ sub process {
>>   		#print "==>$rawline\n";
>>   		#print "-->$line\n";
>>   	}
>> +	$blank_only_hunk{$hunk_first_blank} = 1
>> +		if ($hunk_first_blank && !$hunk_has_change);
>>   
>>   	$prefix = '';
>>   
>> @@ -1780,6 +1797,10 @@ sub process {
>>   
>>   		$cnt_lines++ if ($realcnt != 0);
>>   
>> +		if ($blank_only_hunk{$linenr}) {
>> +			WARN("this hunk only adds blank lines\n" . $herecurr);
>> +		}
>> +
>>   # Only allow Python 3 interpreter
>>   		if ($realline == 1 &&
>>   			$line =~ /^\+#!\ *\/usr\/bin\/(?:env )?python$/) {
>>
>> base-commit: e1705a25aff35635c360bbaba4c2731d019a422a
> Guys,
> 
> does it make sense to continue discussion or this patch
> goes to /dev/null as nobody is interested in?
  Hi,

sorry, but I still don't have a proper clue whether this is really a good 
idea or not. There could also be valid cases where a hunk that adds a single 
blank line could be fine ... so I'd tend to rather not add this patch? What 
do others think?

  Thomas