linux-kernel - Re: [RFC] scripts: kernel-doc: reduce repeated regex expressions into variables

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Date:   Fri, 23 Apr 2021 14:21:17 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Aditya Srivastava <yashsri421@...il.com>
Cc:     corbet@....net, lukas.bulwahn@...il.com,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] scripts: kernel-doc: reduce repeated regex expressions
 into variables

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?

> @@ -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.

> -    } 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/) {