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]
sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.
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 <gustavoars@xxxxxxxxxx>
---
drivers/net/wireless/ath/carl9170/fwcmd.h | 2 +-
drivers/net/wireless/ath/carl9170/hw.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/wireless/ath/carl9170/fwcmd.h b/drivers/net/wireless/ath/carl9170/fwcmd.h
index ea1d80f9a50e..56999a3b9d3b 100644
--- a/drivers/net/wireless/ath/carl9170/fwcmd.h
+++ b/drivers/net/wireless/ath/carl9170/fwcmd.h
@@ -127,7 +127,7 @@ struct carl9170_write_reg {
struct carl9170_write_reg_byte {
__le32 addr;
__le32 count;
- u8 val[0];
+ u8 val[];
} __packed;
#define CARL9170FW_PHY_HT_ENABLE 0x4
diff --git a/drivers/net/wireless/ath/carl9170/hw.h b/drivers/net/wireless/ath/carl9170/hw.h
index 08e0ae9c5836..555ad4975970 100644
--- a/drivers/net/wireless/ath/carl9170/hw.h
+++ b/drivers/net/wireless/ath/carl9170/hw.h
@@ -851,7 +851,7 @@ struct ar9170_stream {
__le16 length;
__le16 tag;
- u8 payload[0];
+ u8 payload[];
} __packed __aligned(4);
#define AR9170_STREAM_LEN 4
