Linux Input Archive on lore.kernel.org
 help / color / Atom feed
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
	"Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: [PATCH] Input: tca6416-keypad - replace zero-length array with flexible-array member
Date: Fri, 14 Feb 2020 11:20:22 -0600
Message-ID: <20200214172022.GA27490@embeddedor> (raw)

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/input/keyboard/tca6416-keypad.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/input/keyboard/tca6416-keypad.c b/drivers/input/keyboard/tca6416-keypad.c
index 2a14769de637..21758767ccf0 100644
--- a/drivers/input/keyboard/tca6416-keypad.c
+++ b/drivers/input/keyboard/tca6416-keypad.c
@@ -33,7 +33,7 @@ MODULE_DEVICE_TABLE(i2c, tca6416_id);
 
 struct tca6416_drv_data {
 	struct input_dev *input;
-	struct tca6416_button data[0];
+	struct tca6416_button data[];
 };
 
 struct tca6416_keypad_chip {
@@ -48,7 +48,7 @@ struct tca6416_keypad_chip {
 	int irqnum;
 	u16 pinmask;
 	bool use_polling;
-	struct tca6416_button buttons[0];
+	struct tca6416_button buttons[];
 };
 
 static int tca6416_write_reg(struct tca6416_keypad_chip *chip, int reg, u16 val)
-- 
2.25.0


             reply index

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-14 17:20 Gustavo A. R. Silva [this message]
2020-02-15 23:30 ` Dmitry Torokhov

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200214172022.GA27490@embeddedor \
    --to=gustavo@embeddedor.com \
    --cc=dmitry.torokhov@gmail.com \
    --cc=linux-input@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux Input Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-input/0 linux-input/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-input linux-input/ https://lore.kernel.org/linux-input \
		linux-input@vger.kernel.org
	public-inbox-index linux-input

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-input


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git