Hi,
On Sat, Feb 15, 2020 at 2:04 AM 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")
Looks good to me. Thanks.
Reviewed-by: Baolin Wang <baolin.wang7@xxxxxxxxx>
> Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
> ---
> drivers/dma/sprd-dma.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/dma/sprd-dma.c b/drivers/dma/sprd-dma.c
> index 9a31a315dbef..954eff32cc05 100644
> --- a/drivers/dma/sprd-dma.c
> +++ b/drivers/dma/sprd-dma.c
> @@ -212,7 +212,7 @@ struct sprd_dma_dev {
> struct clk *ashb_clk;
> int irq;
> u32 total_chns;
> - struct sprd_dma_chn channels[0];
> + struct sprd_dma_chn channels[];
> };
>
> static void sprd_dma_free_desc(struct virt_dma_desc *vd);
> --
> 2.25.0
>
