On Thu, Feb 20, 2020 at 07:20:17AM -0600, Gustavo A. R. Silva wrote:

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 <redacted>
---
 drivers/usb/atm/usbatm.h              | 2 +-
 drivers/usb/dwc2/hcd.h                | 2 +-
 drivers/usb/host/ehci-tegra.c         | 2 +-
 drivers/usb/host/ehci.h               | 4 ++--
 drivers/usb/host/fotg210.h            | 2 +-
 drivers/usb/host/ohci.h               | 4 ++--
 drivers/usb/host/xhci-mtk.h           | 2 +-
 drivers/usb/host/xhci.h               | 4 ++--
 drivers/usb/serial/io_usbvend.h       | 4 ++--
 drivers/usb/serial/ti_usb_3410_5052.c | 4 ++--
 include/linux/usb.h                   | 4 ++--
 include/linux/usb/audio-v2.h          | 2 +-
 include/linux/usb/audio-v3.h          | 2 +-
 include/linux/usb/gadget.h            | 2 +-
 include/linux/usb/hcd.h               | 2 +-
 include/linux/usbdevice_fs.h          | 2 +-
 16 files changed, 22 insertions(+), 22 deletions(-)

Looks like your scripts still doesn't catch every instance. A simple
grep like 

	git grep -A1 '\[0\];$' drivers/usb/ | grep -B1 '}'

found at least three more in 

	drivers/usb/atm/ueagle-atm.c
	drivers/usb/gadget/function/f_phonet.c
	drivers/usb/musb/musb_host.c

Johan

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