linux-kernel - Re: [PATCH] checkpatch: fix multi-statement macro checks for while blocks.

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Message-ID: <c5e3b0067f32bc16f90390c51162b47f257935ac.camel@perches.com>
Date:   Thu, 01 Oct 2020 10:25:04 -0700
From:   Joe Perches <joe@...ches.com>
To:     Dwaipayan Ray <dwaipayanray1@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        lukas.bulwahn@...il.com, Andy Whitcroft <apw@...onical.com>
Subject: Re: [PATCH] checkpatch: fix multi-statement macro checks for while
 blocks.

On Thu, 2020-10-01 at 22:49 +0530, Dwaipayan Ray wrote:
> Checkpatch.pl doesn't have a check for excluding while (...) {...}
> blocks from MULTISTATEMENT_MACRO_USE_DO_WHILE error.
> 
> For example, running checkpatch.pl on the file mm/maccess.c in the
> kernel generates the following error:
> 
> ERROR: Macros with complex values should be enclosed in parentheses
> +#define copy_from_kernel_nofault_loop(dst, src, len, type, err_label)  \
> +       while (len >= sizeof(type)) {                                   \
> +               __get_kernel_nofault(dst, src, type, err_label);        \
> +               dst += sizeof(type);                                    \
> +               src += sizeof(type);                                    \
> +               len -= sizeof(type);                                    \
> +       }
> 
> The error is misleading for this case. Enclosing it in parentheses
> doesn't make any sense.
> 
> Checkpatch already has an exception list for such common macro types.
> Added a new exception for while (...) {...} style blocks to the same.
> 
> In addition, the brace flatten logic was modified by changing the
> substitution characters from "1" to "1u". This was done to ensure that
> macros in the form "#define foo(bar) while(bar){bar--;}" were also
> correctly procecssed.
> 
> Link: https://lore.kernel.org/linux-kernel-mentees/dc985938aa3986702815a0bd68dfca8a03c85447.camel@perches.com/
> 
> Suggested-by: Joe Perches <joe@...ches.com>
> Signed-off-by: Dwaipayan Ray <dwaipayanray1@...il.com>

Thanks.  Andrew, can you pick this up please?

> ---
>  scripts/checkpatch.pl | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 9e65d21456f1..31624bbb342e 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -5299,9 +5299,9 @@ sub process {
>  			$dstat =~ s/\s*$//s;
>  
>  			# Flatten any parentheses and braces
> -			while ($dstat =~ s/\([^\(\)]*\)/1/ ||
> -			       $dstat =~ s/\{[^\{\}]*\}/1/ ||
> -			       $dstat =~ s/.\[[^\[\]]*\]/1/)
> +			while ($dstat =~ s/\([^\(\)]*\)/1u/ ||
> +			       $dstat =~ s/\{[^\{\}]*\}/1u/ ||
> +			       $dstat =~ s/.\[[^\[\]]*\]/1u/)
>  			{
>  			}
>  
> @@ -5342,6 +5342,7 @@ sub process {
>  			    $dstat !~ /^\.$Ident\s*=/ &&				# .foo =
>  			    $dstat !~ /^(?:\#\s*$Ident|\#\s*$Constant)\s*$/ &&		# stringification #foo
>  			    $dstat !~ /^do\s*$Constant\s*while\s*$Constant;?$/ &&	# do {...} while (...); // do {...} while (...)
> +			    $dstat !~ /^while\s*$Constant\s*$Constant\s*$/ &&		# while (...) {...}
>  			    $dstat !~ /^for\s*$Constant$/ &&				# for (...)
>  			    $dstat !~ /^for\s*$Constant\s+(?:$Ident|-?$Constant)$/ &&	# for (...) bar()
>  			    $dstat !~ /^do\s*{/ &&					# do {...