linux-kernel - Re: new checkpatch flexible array test ? (was Re: [PATCH v4 12/14] gunyah: rsc

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Date:   Sun, 02 Oct 2022 22:38:51 -0700
From:   Joe Perches <joe@...ches.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Elliot Berman <quic_eberman@...cinc.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Bjorn Andersson <quic_bjorande@...cinc.com>,
        Murali Nalajala <quic_mnalajal@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
        Carl van Schaik <quic_cvanscha@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Marc Zyngier <maz@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Arnd Bergmann <arnd@...db.de>, devicetree@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: new checkpatch flexible array test ?  (was Re: [PATCH v4 12/14]
 gunyah: rsc_mgr: Add RPC for console services)

On Mon, 2022-10-03 at 07:29 +0200, Greg Kroah-Hartman wrote:
> On Sun, Oct 02, 2022 at 06:46:30PM -0700, Joe Perches wrote:
> > On Fri, 2022-09-30 at 14:22 +0200, Greg Kroah-Hartman wrote:
> > > On Wed, Sep 28, 2022 at 12:56:31PM -0700, Elliot Berman wrote:
> > > > Gunyah resource manager defines a simple API for virtual machine log
> > > > sharing with the console service.
> > []
> > > > diff --git a/include/linux/gunyah_rsc_mgr.h b/include/linux/gunyah_rsc_mgr.h
> > []
> > > > +struct gh_rm_notif_vm_console_chars {
> > > > +	u16 vmid;
> > > > +	u16 num_bytes;
> > > > +	u8 bytes[0];
> > > 
> > > Please do not use [0] for new structures, otherwise we will just have to
> > > fix them up again as we are trying to get rid of all of these from the
> > > kernel. Just use "bytes[];" instead.
> > 
> > Maybe a checkpatch addition like:
> > ---
[]
> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> > @@ -3948,6 +3948,17 @@ sub process {
> >  			}
> >  		}
> >  
> > +# check for zero length array declarations in likely structs
> > +		if ($line =~ /^\+\t($Declare\s*$Ident)\s*\[\s*0\s*\]\s*;\s*$/ &&
> > +		    defined $lines[$linenr] &&
> > +		    $lines[$linenr] =~ /^[\+ ]\}\s*(?:__\w+\s*(?:$balanced_parens)?)\s*;\s*$/) {

This should actually be:

		    $lines[$linenr] =~ /^[\+ ]\}(?:\s*__\w+\s*(?:$balanced_parens)?)*\s*;\s*$/) {

as it was missing a * for uses like

	int foo[0];
} __packed __aligned(4);

and uses without any attribute at all

> > +			if (WARN("FLEXIBLE_ARRAY_ZERO",
> > +				 "Prefer flexible length array declarations with [] over [0]\n" . $herecurr) &&
> > +			    $fix) {
> > +				$fixed[$fixlinenr] =~ s/\[\s*0\s*\]/[]/;
> > +			}
> > +		}
> > +
> >  # check for multiple consecutive blank lines
> >  		if ($prevline =~ /^[\+ ]\s*$/ &&
> >  		    $line =~ /^\+\s*$/ &&
> 
> This is a question for Gustavo, who did all the work here.  Gustavo,
> does the above checkpatch change look good to you?