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Date: Wed, 17 Jan 2024 09:32:34 -0500
From: Steven Rostedt <rostedt@goodmis.org>
To: Nathan Lynch via B4 Relay <devnull+nathanl.linux.ibm.com@kernel.org>
Cc: <nathanl@linux.ibm.com>, Kees Cook <keescook@chromium.org>,
 linux-kernel@vger.kernel.org
Subject: Re: [PATCH] seq_buf: make DECLARE_SEQ_BUF() usable
Message-ID: <20240117093234.660d4150@gandalf.local.home>
In-Reply-To: <20240116-declare-seq-buf-fix-v1-1-915db4692f32@linux.ibm.com>
References: <20240116-declare-seq-buf-fix-v1-1-915db4692f32@linux.ibm.com>
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Kees,

Are you OK with this change? I ran it through my tests and have another
pull request ready to go that includes this. But I don't want to send it
without an Acked-by from you.

Luckily, Linus is on non-voluntary vacation so we may still have time ;-)

-- Steve


On Tue, 16 Jan 2024 08:09:25 -0600
Nathan Lynch via B4 Relay <devnull+nathanl.linux.ibm.com@kernel.org> wrote:

> From: Nathan Lynch <nathanl@linux.ibm.com>
>=20
> Using the address operator on the array doesn't work:
>=20
> ./include/linux/seq_buf.h:27:27: error: initialization of =E2=80=98char *=
=E2=80=99
>   from incompatible pointer type =E2=80=98char (*)[128]=E2=80=99
>   [-Werror=3Dincompatible-pointer-types]
>    27 |                 .buffer =3D &__ ## NAME ## _buffer,       \
>       |                           ^
>=20
> Apart from fixing that, we can improve DECLARE_SEQ_BUF() by using a
> compound literal to define the buffer array without attaching a name
> to it. This makes the macro a single statement, allowing constructs
> such as:
>=20
>   static DECLARE_SEQ_BUF(my_seq_buf, MYSB_SIZE);
>=20
> to work as intended.
>=20
> Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
> Fixes: dcc4e5728eea ("seq_buf: Introduce DECLARE_SEQ_BUF and seq_buf_str(=
)")
> ---
>  include/linux/seq_buf.h | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>=20
> diff --git a/include/linux/seq_buf.h b/include/linux/seq_buf.h
> index 5fb1f12c33f9..c44f4b47b945 100644
> --- a/include/linux/seq_buf.h
> +++ b/include/linux/seq_buf.h
> @@ -22,9 +22,8 @@ struct seq_buf {
>  };
> =20
>  #define DECLARE_SEQ_BUF(NAME, SIZE)			\
> -	char __ ## NAME ## _buffer[SIZE] =3D "";		\
>  	struct seq_buf NAME =3D {				\
> -		.buffer =3D &__ ## NAME ## _buffer,	\
> +		.buffer =3D (char[SIZE]) { 0 },		\
>  		.size =3D SIZE,				\
>  	}
> =20
>=20
> ---
> base-commit: 70d201a40823acba23899342d62bc2644051ad2e
> change-id: 20240112-declare-seq-buf-fix-9803b7e679bc
>=20
> Best regards,