linux-kernel - [PATCH] seq_buf: make DECLARE_SEQ

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Date: Tue, 16 Jan 2024 08:09:25 -0600
From: Nathan Lynch via B4 Relay <devnull+nathanl.linux.ibm.com@...nel.org>
To: "Steven Rostedt (Google)" <rostedt@...dmis.org>, 
 Kees Cook <keescook@...omium.org>
Cc: linux-kernel@...r.kernel.org, Nathan Lynch <nathanl@...ux.ibm.com>
Subject: [PATCH] seq_buf: make DECLARE_SEQ_BUF() usable

From: Nathan Lynch <nathanl@...ux.ibm.com>

Using the address operator on the array doesn't work:

/include/linux/seq_buf.h:27:27: error: initialization of ‘char *’
  from incompatible pointer type ‘char (*)[128]’
  [-Werror=incompatible-pointer-types]
   27 |                 .buffer = &__ ## NAME ## _buffer,       \
      |                           ^

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:

  static DECLARE_SEQ_BUF(my_seq_buf, MYSB_SIZE);

to work as intended.

Signed-off-by: Nathan Lynch <nathanl@...ux.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(-)

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 {
 };
 
 #define DECLARE_SEQ_BUF(NAME, SIZE)			\
-	char __ ## NAME ## _buffer[SIZE] = "";		\
 	struct seq_buf NAME = {				\
-		.buffer = &__ ## NAME ## _buffer,	\
+		.buffer = (char[SIZE]) { 0 },		\
 		.size = SIZE,				\
 	}
 

---
base-commit: 70d201a40823acba23899342d62bc2644051ad2e
change-id: 20240112-declare-seq-buf-fix-9803b7e679bc

Best regards,
-- 
Nathan Lynch <nathanl@...ux.ibm.com>