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From:   Dwaipayan Ray <dwaipayanray1@gmail.com>
Date:   Sun, 25 Apr 2021 13:30:28 +0530
Message-ID: <CABJPP5CGCagfP1NTO5ci-wWNN9AOx2j-4i0Bj6G2mPXeja2jEg@mail.gmail.com>
Subject: Re: [PATCH v2] checkpatch: fix uninitialized return value in raw_line subroutine
To:     Joe Perches <joe@perches.com>
Cc:     linux-kernel <linux-kernel@vger.kernel.org>,
        Lukas Bulwahn <lukas.bulwahn@gmail.com>
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On Sun, Apr 25, 2021 at 1:14 PM Dwaipayan Ray <dwaipayanray1@gmail.com> wrote:
>
> In case the second argument to raw_line subroutine is 0,
> $line remains uninitialized and is returned back to the caller.
> If the caller then tries to perform string concatenation with
> that value, checkpatch throws an error:
>
> Use of uninitialized value in concatenation (.) or string at
> ./scripts/checkpatch.pl line 1960.
>
> Fix it by providing an empty string as the initial value
> for $line.
>

Please ignore this patch. There was a different problem which
caused the error.

The following line triggers the errors:
DEVICE_ATTR(foo, 0777, foo_show, foo_store)
(notice the missing semicolon)

Perl throws the following errors when checkpatch is run on
a file containing that line:

Use of uninitialized value in concatenation (.) or string at
./scripts/checkpatch.pl line 1960.
Use of uninitialized value in concatenation (.) or string at
./scripts/checkpatch.pl line 1960.
Use of uninitialized value in concatenation (.) or string at
./scripts/checkpatch.pl line 1960.
Use of uninitialized value in concatenation (.) or string at
./scripts/checkpatch.pl line 1960.
Use of uninitialized value in concatenation (.) or string at
./scripts/checkpatch.pl line 1960.
Use of uninitialized value in concatenation (.) or string at
./scripts/checkpatch.pl line 1960.
Use of uninitialized value in concatenation (.) or string at
./scripts/checkpatch.pl line 1960.
Use of uninitialized value in concatenation (.) or string at
./scripts/checkpatch.pl line 1960.
Use of uninitialized value in concatenation (.) or string at
./scripts/checkpatch.pl line 1960.
Use of uninitialized value in concatenation (.) or string at
./scripts/checkpatch.pl line 1960.

Setting $line to "" in raw_line fixed it. Probably -1 is being
sent as the second argument to raw_line which results
in the uninitialized thing.

Thanks,
Dwaipayan