intel-ish-hid: ishtp: hbm.h: Replace zero-length array with flexible-array member
Subsystems (2)
PATCH 1/1 intel-ish-hid: ishtp: hbm.h: 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/hid/intel-ish-hid/ishtp/hbm.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
drivers/hid/intel-ish-hid/ishtp/hbm.h +1 -1
@@ -82,7 +82,7 @@ struct ishtp_msg_hdr {struct ishtp_bus_message {uint8_t hbm_cmd; -uint8_t data[0 ]; +uint8_t data[]; } __packed;/**
Signature · 1 line
2.23.0
Quoted 38 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]
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]>--- drivers/hid/intel-ish-hid/ishtp/hbm.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)drivers/hid/intel-ish-hid/ishtp/hbm.h +0
-0
drivers/hid/intel-ish-hid/ishtp/hbm.h struct ishtp_msg_hdr { · line 88
Quoted 8 lines
drivers/hid/intel-ish-hid/ishtp/hbm.h +1
-1@@ -82,7 +82,7 @@ struct ishtp_msg_hdr {struct ishtp_bus_message {uint8_t hbm_cmd; -uint8_t data[0 ]; +uint8_t data[]; } __packed;/**
Applied this one too, thanks Gustavo.
Signature · 2 lines
Jiri Kosina SUSE Labs
Quoted 3 lines · Jiri Kosina
Applied this one too, thanks Gustavo.
Awesome. :)
Thanks, Jiri.
--
Gustavo