From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Linus Walleij <linus.walleij@linaro.org>,
Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: linux-gpio@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
"Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: [PATCH] pinctrl: uniphier: Replace zero-length array with flexible-array member
Date: Mon, 17 Feb 2020 12:54:37 -0600 [thread overview]
Message-ID: <20200217185437.GA20901@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/pinctrl/uniphier/pinctrl-uniphier-core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/pinctrl/uniphier/pinctrl-uniphier-core.c b/drivers/pinctrl/uniphier/pinctrl-uniphier-core.c
index 57babf31e320..ade348b49b31 100644
--- a/drivers/pinctrl/uniphier/pinctrl-uniphier-core.c
+++ b/drivers/pinctrl/uniphier/pinctrl-uniphier-core.c
@@ -29,7 +29,7 @@ struct uniphier_pinctrl_reg_region {
struct list_head node;
unsigned int base;
unsigned int nregs;
- u32 vals[0];
+ u32 vals[];
};
struct uniphier_pinctrl_priv {
--
2.25.0
next reply other threads:[~2020-02-17 18:52 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-17 18:54 Gustavo A. R. Silva [this message]
2020-02-18 1:24 ` [PATCH] pinctrl: uniphier: Replace zero-length array with flexible-array member Masahiro Yamada
2020-02-21 14:37 ` Linus Walleij
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