p54: Replace zero-length array with flexible-array member
Subsystems (3)
PATCH 1/1 p54: 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/wireless/intersil/p54/eeprom.h | 8 ++++---- drivers/net/wireless/intersil/p54/lmac.h | 6 +++--- drivers/net/wireless/intersil/p54/p54.h | 2 +- 3 files changed, 8 insertions(+), 8 deletions(-)
drivers/net/wireless/intersil/p54/eeprom.h +4 -4
@@ -24,7 +24,7 @@struct pda_entry {__le16 len;/* includes both code and data */ __le16 code; -u8 data[0 ]; +u8 data[]; } __packed;struct eeprom_pda_wrap {
@@ -32,7 +32,7 @@ struct eeprom_pda_wrap {__le16 pad;__le16 len;__le32 arm_opcode; -u8 data[0 ]; +u8 data[]; } __packed;struct p54_iq_autocal_entry {
@@ -87,7 +87,7 @@ struct pda_pa_curve_data {u8 channels;u8 points_per_channel;u8 padding; -u8 data[0 ]; +u8 data[]; } __packed;struct pda_rssi_cal_ext_entry {
@@ -119,7 +119,7 @@ struct pda_custom_wrapper {__le16 entry_size;__le16 offset;__le16 len; -u8 data[0 ]; +u8 data[]; } __packed;/*
drivers/net/wireless/intersil/p54/lmac.h +3 -3
@@ -81,7 +81,7 @@ struct p54_hdr {__le16 type;/* enum p54_control_frame_types */ u8 rts_tries;u8 tries; -u8 data[0 ]; +u8 data[]; } __packed;#define GET_REQ_ID (skb) \
@@ -176,7 +176,7 @@ struct p54_rx_data {u8 rssi_raw;__le32 tsf32;__le32 unalloc0; -u8 align[0 ]; +u8 align[]; } __packed;enum p54_trap_type {
@@ -267,7 +267,7 @@ struct p54_tx_data { }__packed normal; } __packed;u8 unalloc2[2 ]; -u8 align[0 ]; +u8 align[]; } __packed;/* unit is ms */
drivers/net/wireless/intersil/p54/p54.h +1 -1
@@ -126,7 +126,7 @@ struct p54_cal_database {size_t entry_size;size_t offset;size_t len; -u8 data[0 ]; +u8 data[]; };#define EEPROM_READBACK_LEN 0x3fc
Signature · 1 line
2.25.0
Quoted 22 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:
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]>
Patch applied to wireless-drivers-next.git, thanks.
7b9307134058 p54: Replace zero-length array with flexible-array member
Signature · 3 lines
https://patchwork.kernel.org/patch/11402365/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches