From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Wu Hao <hao.wu@intel.com>, Moritz Fischer <mdf@kernel.org>
Cc: linux-fpga@vger.kernel.org, linux-kernel@vger.kernel.org,
"Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: [PATCH][next] fpga: dfl.h: Replace zero-length array with flexible-array member
Date: Thu, 19 Mar 2020 16:21:53 -0500 [thread overview]
Message-ID: <20200319212153.GA5093@embeddedor.com> (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/fpga/dfl.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/fpga/dfl.h b/drivers/fpga/dfl.h
index 4a9a33cd9979..74784d3cfe7c 100644
--- a/drivers/fpga/dfl.h
+++ b/drivers/fpga/dfl.h
@@ -235,7 +235,7 @@ struct dfl_feature_platform_data {
int open_count;
void *private;
int num;
- struct dfl_feature features[0];
+ struct dfl_feature features[];
};
static inline
--
2.23.0
next reply other threads:[~2020-03-19 21:21 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-19 21:21 Gustavo A. R. Silva [this message]
2020-03-21 20:10 ` [PATCH][next] fpga: dfl.h: Replace zero-length array with flexible-array member Moritz Fischer
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