toshiba: Replace zero-length array with flexible-array member
Subsystems (4)
PATCH 1/1 toshiba: Replace zero-length array with flexible-array member
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")
--- drivers/net/ethernet/toshiba/ps3_gelic_net.h | 2 +- drivers/net/ethernet/toshiba/ps3_gelic_wireless.h | 2 +- drivers/net/ethernet/toshiba/spider_net.h | 2 +- drivers/net/ethernet/toshiba/tc35815.c | 2 +- 4 files changed, 4 insertions(+), 4 deletions(-)
drivers/net/ethernet/toshiba/ps3_gelic_net.h +1 -1
@@ -308,7 +308,7 @@ struct gelic_port {struct gelic_card *card;struct net_device *netdev;enum gelic_port_type type; -long priv[0 ];/* long for alignment */ +long priv[];/* long for alignment */ };static inline struct gelic_card *port_to_card (struct gelic_port *p)
drivers/net/ethernet/toshiba/ps3_gelic_wireless.h +1 -1
@@ -158,7 +158,7 @@ struct gelic_eurus_scan_info {__be32 reserved2;__be32 reserved3;__be32 reserved4; -u8 elements[0 ];/* ie */ +u8 elements[];/* ie */ } __packed;/* the hypervisor returns bbs up to 16 */
drivers/net/ethernet/toshiba/spider_net.h +1 -1
@@ -470,7 +470,7 @@ struct spider_net_card {struct spider_net_extra_stats spider_stats;/* Must be last item in struct */ - struct spider_net_descr darray[0]; + struct spider_net_descr darray[]; };#endif
drivers/net/ethernet/toshiba/tc35815.c +1 -1
@@ -367,7 +367,7 @@ struct TxFD {struct RxFD {struct FDesc fd; -struct BDesc bd[0 ];/* variable length */ +struct BDesc bd[];/* variable length */ };struct FrFD {
Signature · 1 line
2.25.0
From: "Gustavo A. R. Silva" <[email protected]>
Date: Mon, 24 Feb 2020 10:32:52 -0600
Quoted 22 lines
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]
Quoted 7 lines
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] commit76497732932f("cxgb3/l2t: Fix undefined behaviour")Signed-off-by Gustavo A. R. Silva <[email protected]>
Applied.
Quoted 4 lines · Gustavo A. R. Silva
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:
Seems fine.