On Thu, Mar 19, 2020 at 9:15 PM Gustavo A. R. Silva
<gustavo@xxxxxxxxxxxxxx> 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 <gustavo@xxxxxxxxxxxxxx>
Dan,
I'm assuming that you will take care of this one or please let me know
otherwise.
Cheers!
> ---
> drivers/acpi/nfit/nfit.h | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/acpi/nfit/nfit.h b/drivers/acpi/nfit/nfit.h
> index 24241941181c..af09143ce403 100644
> --- a/drivers/acpi/nfit/nfit.h
> +++ b/drivers/acpi/nfit/nfit.h
> @@ -144,32 +144,32 @@ struct nfit_spa {
> unsigned long ars_state;
> u32 clear_err_unit;
> u32 max_ars;
> - struct acpi_nfit_system_address spa[0];
> + struct acpi_nfit_system_address spa[];
> };
>
> struct nfit_dcr {
> struct list_head list;
> - struct acpi_nfit_control_region dcr[0];
> + struct acpi_nfit_control_region dcr[];
> };
>
> struct nfit_bdw {
> struct list_head list;
> - struct acpi_nfit_data_region bdw[0];
> + struct acpi_nfit_data_region bdw[];
> };
>
> struct nfit_idt {
> struct list_head list;
> - struct acpi_nfit_interleave idt[0];
> + struct acpi_nfit_interleave idt[];
> };
>
> struct nfit_flush {
> struct list_head list;
> - struct acpi_nfit_flush_address flush[0];
> + struct acpi_nfit_flush_address flush[];
> };
>
> struct nfit_memdev {
> struct list_head list;
> - struct acpi_nfit_memory_map memdev[0];
> + struct acpi_nfit_memory_map memdev[];
> };
>
> enum nfit_mem_flags {
> --
> 2.23.0
>
