linux-kernel - Re: [PATCH] checkpatch: Check for illegal return codes

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Date:   Tue, 03 Jul 2018 11:19:27 -0700
From:   Joe Perches <joe@...ches.com>
To:     Prakruthi Deepak Heragu <pheragu@...eaurora.org>, apw@...onical.com
Cc:     linux-kernel@...r.kernel.org, ckadabi@...eaurora.org,
        tsoni@...eaurora.org, bryanh@...eaurora.org,
        Patrick Pannuto <ppannuto@...eaurora.org>,
        Stepan Moskovchenko <stepanm@...eaurora.org>
Subject: Re: [PATCH] checkpatch: Check for illegal return codes

On Tue, 2018-07-03 at 11:09 -0700, Prakruthi Deepak Heragu wrote:
> The only legal integer return is 0, anything else
> following "return" should be -ERRCODE or a function.
> 
> http://lkml.org/lkml/2010/7/23/318
>   There's lots of "return -1;" statements in this patch - it's obscene
>   that this is used to indicate "some error occurred" in kernel space
>   rather than a real errno value - even when an existing function
>   (eg, request_irq) gave you an error code already.
> 
> Signed-off-by: Patrick Pannuto <ppannuto@...eaurora.org>
> Signed-off-by: Stepan Moskovchenko <stepanm@...eaurora.org>
> Signed-off-by: Prakruthi Deepak Heragu <pheragu@...eaurora.org>
> ---
>  scripts/checkpatch.pl | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index a9c0550..260d252 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -6197,6 +6197,12 @@ sub process {
>  			     "switch default: should use break\n" . $herectx);
>  		}
>  
> +# check for return codes on error paths
> +		if ($line =~ /\breturn\s+-\d+/) {
> +			ERROR("NO_ERROR_CODE",
> +			      "illegal return value, please use an error code");
> +		}
> +

Substitute illegal to invalid as this wouldn't be illegal.
It might be invalid and this needs a newline and $herecurr

I'm not sure this is even useful.

There are _way_ too many of these already existing
and simple return identifiers can be OK.

$ git grep -P '\breturn\s*\-(?!0)\d+' | wc -l
10193

and

$ git grep -P '\breturn\s*\-(?!1)\d+' | wc -l
240