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From:   Aditya Srivastava <yashsri421@gmail.com>
Subject: Re: [RFC] scripts: kernel-doc: reduce repeated regex expressions into
 variables
To:     Matthew Wilcox <willy@infradead.org>
Cc:     corbet@lwn.net, lukas.bulwahn@gmail.com,
        linux-kernel-mentees@lists.linuxfoundation.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20210422191839.6119-1-yashsri421@gmail.com>
 <20210423132117.GB235567@casper.infradead.org>
Message-ID: <6f76ddcb-7076-4c91-9c4c-995002c4cb91@gmail.com>
Date:   Sat, 24 Apr 2021 17:27:34 +0530
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On 23/4/21 6:51 pm, Matthew Wilcox wrote:
> On Fri, Apr 23, 2021 at 12:48:39AM +0530, Aditya Srivastava wrote:
>> +my $pointer_function = qr{([^\(]*\(\*)\s*\)\s*\(([^\)]*)\)};
> 
> Is that a pointer-to-function?  Or as people who write C usually call it,
> a function pointer?  Wouldn't it be better to call it $function_pointer?
> 
Will do it.

>> @@ -1210,8 +1211,14 @@ sub dump_struct($$) {
>>      my $decl_type;
>>      my $members;
>>      my $type = qr{struct|union};
>> +    my $packed = qr{__packed};
>> +    my $aligned = qr{__aligned};
>> +    my $cacheline_aligned_in_smp = qr{____cacheline_aligned_in_smp};
>> +    my $cacheline_aligned = qr{____cacheline_aligned};
> 
> I don't think those four definitions actually simplify anything.
> 
>> +    my $attribute = qr{__attribute__\s*\(\([a-z0-9,_\*\s\(\)]*\)\)}i;
> 
> ... whereas this one definitely does.
> 
>> -	$members =~ s/\s*__attribute__\s*\(\([a-z0-9,_\*\s\(\)]*\)\)/ /gi;
>> -	$members =~ s/\s*__aligned\s*\([^;]*\)/ /gos;
>> -	$members =~ s/\s*__packed\s*/ /gos;
>> +	$members =~ s/\s*$attribute/ /gi;
>> +	$members =~ s/\s*$aligned\s*\([^;]*\)/ /gos;
> 
> Maybe put the \s*\([^;]*\) into $aligned?  Then it becomes a useful
> abstraction.

Actually, I had made these variables as they were repeated here and at
-    my $definition_body =
qr{\{(.*)\}(?:\s*(?:__packed|__aligned|____cacheline_aligned_in_smp|____cacheline_aligned|__attribute__\s*\(\([a-z0-9,_\s\(\)]*\)\)))*};
+    my $definition_body =
qr{\{(.*)\}(?:\s*(?:$packed|$aligned|$cacheline_aligned_in_smp|$cacheline_aligned|$attribute))*};

So, defining them at a place might help.

What do you think?

> 
>> -    } elsif ($prototype =~ m/^()([a-zA-Z0-9_~:]+)\s*\(([^\(]*)\)/ ||
>> -	$prototype =~ m/^(\w+)\s+([a-zA-Z0-9_~:]+)\s*\(([^\(]*)\)/ ||
>> -	$prototype =~ m/^(\w+\s*\*+)\s*([a-zA-Z0-9_~:]+)\s*\(([^\(]*)\)/ ||
>> -	$prototype =~ m/^(\w+\s+\w+)\s+([a-zA-Z0-9_~:]+)\s*\(([^\(]*)\)/ ||
>> -	$prototype =~ m/^(\w+\s+\w+\s*\*+)\s*([a-zA-Z0-9_~:]+)\s*\(([^\(]*)\)/ ||
>> -	$prototype =~ m/^(\w+\s+\w+\s+\w+)\s+([a-zA-Z0-9_~:]+)\s*\(([^\(]*)\)/ ||
>> -	$prototype =~ m/^(\w+\s+\w+\s+\w+\s*\*+)\s*([a-zA-Z0-9_~:]+)\s*\(([^\(]*)\)/ ||
>> -	$prototype =~ m/^()([a-zA-Z0-9_~:]+)\s*\(([^\{]*)\)/ ||
>> -	$prototype =~ m/^(\w+)\s+([a-zA-Z0-9_~:]+)\s*\(([^\{]*)\)/ ||
>> -	$prototype =~ m/^(\w+\s*\*+)\s*([a-zA-Z0-9_~:]+)\s*\(([^\{]*)\)/ ||
>> -	$prototype =~ m/^(\w+\s+\w+)\s+([a-zA-Z0-9_~:]+)\s*\(([^\{]*)\)/ ||
>> -	$prototype =~ m/^(\w+\s+\w+\s*\*+)\s*([a-zA-Z0-9_~:]+)\s*\(([^\{]*)\)/ ||
>> -	$prototype =~ m/^(\w+\s+\w+\s+\w+)\s+([a-zA-Z0-9_~:]+)\s*\(([^\{]*)\)/ ||
>> -	$prototype =~ m/^(\w+\s+\w+\s+\w+\s*\*+)\s*([a-zA-Z0-9_~:]+)\s*\(([^\{]*)\)/ ||
>> -	$prototype =~ m/^(\w+\s+\w+\s+\w+\s+\w+)\s+([a-zA-Z0-9_~:]+)\s*\(([^\{]*)\)/ ||
>> -	$prototype =~ m/^(\w+\s+\w+\s+\w+\s+\w+\s*\*+)\s*([a-zA-Z0-9_~:]+)\s*\(([^\{]*)\)/ ||
>> -	$prototype =~ m/^(\w+\s+\w+\s*\*+\s*\w+\s*\*+\s*)\s*([a-zA-Z0-9_~:]+)\s*\(([^\{]*)\)/)  {
>> +    } elsif ($prototype =~ m/^()($name)\s*$prototype_end1/ ||
>> +	$prototype =~ m/^(\w+)\s+($name)\s*$prototype_end1/ ||
>> +	$prototype =~ m/^(\w+\s*\*+)\s*($name)\s*$prototype_end1/ ||
>> +	$prototype =~ m/^(\w+\s+\w+)\s+($name)\s*$prototype_end1/ ||
>> +	$prototype =~ m/^(\w+\s+\w+\s*\*+)\s*($name)\s*$prototype_end1/ ||
>> +	$prototype =~ m/^(\w+\s+\w+\s+\w+)\s+($name)\s*$prototype_end1/ ||
>> +	$prototype =~ m/^(\w+\s+\w+\s+\w+\s*\*+)\s*($name)\s*$prototype_end1/ ||
>> +	$prototype =~ m/^()($name)\s*$prototype_end2/ ||
>> +	$prototype =~ m/^(\w+)\s+($name)\s*$prototype_end2/ ||
>> +	$prototype =~ m/^(\w+\s*\*+)\s*($name)\s*$prototype_end2/ ||
>> +	$prototype =~ m/^(\w+\s+\w+)\s+($name)\s*$prototype_end2/ ||
>> +	$prototype =~ m/^(\w+\s+\w+\s*\*+)\s*($name)\s*$prototype_end2/ ||
>> +	$prototype =~ m/^(\w+\s+\w+\s+\w+)\s+($name)\s*$prototype_end2/ ||
>> +	$prototype =~ m/^(\w+\s+\w+\s+\w+\s*\*+)\s*($name)\s*$prototype_end2/ ||
>> +	$prototype =~ m/^(\w+\s+\w+\s+\w+\s+\w+)\s+($name)\s*$prototype_end2/ ||
>> +	$prototype =~ m/^(\w+\s+\w+\s+\w+\s+\w+\s*\*+)\s*($name)\s*$prototype_end2/ ||
>> +	$prototype =~ m/^(\w+\s+\w+\s*\*+\s*\w+\s*\*+\s*)\s*($name)\s*$prototype_end2/)  {
> 
> This is probably the best patch I've seen so far this year.
> 
> Now, can we go further?  For example:
> 	$prototype_end = $prototype_end1|$prototype_end2
> That would let us cut the number of lines here in half.
> > Can we create a definition for a variable number of \w and \s and '*'
> in the return type?  In fact, can we define a regex that matches a type?
> So this would become:
> 
>> +    } elsif ($prototype =~ m/^($type)\s*($name)\s*$prototype_end/) {
> 

I have been able to reduce these expressions furthermore. Will send a
v2 in few..

Thanks
Aditya