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Subject: Re: [PATCH] checkpatch: fix CONST_STRUCT when
 const_structs.checkpatch is missing
To:     Joe Perches <joe@perches.com>, Andy Whitcroft <apw@canonical.com>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-kernel@vger.kernel.org
References: <20200622204844.21030-1-quentin@isovalent.com>
 <8a218fa14cc2e1690df32d278c82587c7507a820.camel@perches.com>
From:   Quentin Monnet <quentin@isovalent.com>
Message-ID: <d2193403-def1-d833-c9bc-0937afca636b@isovalent.com>
Date:   Tue, 23 Jun 2020 11:33:50 +0100
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2020-06-22 14:24 UTC-0700 ~ Joe Perches <joe@perches.com>
> On Mon, 2020-06-22 at 21:48 +0100, Quentin Monnet wrote:
>> Checkpatch reports warnings when some specific structs are not declared
>> as const in the code. The list of structs to consider was initially
>> defined in the checkpatch.pl script itself, but it was later moved to an
>> external file (scripts/const_structs.checkpatch). This introduced two
>> minor issues:
>>
>> - When file scripts/const_structs.checkpatch is not present (for
>>   example, if checkpatch is run outside of the kernel directory with the
>>   "--no-tree" option), a warning is printed to stderr to tell the user
>>   that "No structs that should be const will be found". This is fair,
>>   but the warning is printed unconditionally, even if the option
>>   "--ignore CONST_STRUCT" is passed. In the latter case, we explicitly
>>   ask checkpatch to skip this check, so no warning should be printed.
>>
>> - When scripts/const_structs.checkpatch is missing, or even when trying
>>   to silence the warning by adding an empty file, $const_structs is set
>>   to "", and the regex used for finding structs that should be const,
>>   "$line =~ /\bstruct\s+($const_structs)\b(?!\s*\{)/)", matches all
>>   structs found in the code, thus reporting a number of false positives.
>>
>> Let's fix the first item by skipping scripts/const_structs.checkpatch
>> processing if "CONST_STRUCT" checks are ignored, and the second one by
>> skipping the test if $const_structs is an empty string.
>>
>> Fixes: bf1fa1dae68e ("checkpatch: externalize the structs that should be const")
> 
> Probably not worthy of a Fixes: line, as that's
> generally used for backporting, but OK by me.

Yeah I hesitated, I'll drop it for v2.

> 
>> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> []
>> @@ -781,8 +781,10 @@ sub read_words {
>>  }
>>  
>>  my $const_structs = "";
> 
> This might be a tiny bit faster/less cpu using:
> 
> my $const_structs;
> 
>> -read_words(\$const_structs, $conststructsfile)
>> -    or warn "No structs that should be const will be found - file '$conststructsfile': $!\n";
>> +if (show_type("CONST_STRUCT")) {
>> +	read_words(\$const_structs, $conststructsfile)
>> +	    or warn "No structs that should be const will be found - file '$conststructsfile': $!\n";
>> +}
>>  
>>  my $typeOtherTypedefs = "";
>>  if (length($typedefsfile)) {
>> @@ -6660,7 +6662,8 @@ sub process {
>>  
>>  # check for various structs that are normally const (ops, kgdb, device_tree)
>>  # and avoid what seem like struct definitions 'struct foo {'
>> -		if ($line !~ /\bconst\b/ &&
>> +		if ($const_structs ne "" &&
> 
> instead testing
> 
> 		if (defined($const_structs) &&

Sure, I will respin.

Thank you for the review!
Quentin