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]

sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues.

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 gustavoars@kernel.org --- sound/soc/sof/probe.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/sound/soc/sof/probe.h b/sound/soc/sof/probe.h index 45daa5552834..250c4817f637 100644 --- a/sound/soc/sof/probe.h +++ b/sound/soc/sof/probe.h @@ -36,7 +36,7 @@ struct sof_probe_point_desc { struct sof_ipc_probe_dma_add_params { struct sof_ipc_cmd_hdr hdr; unsigned int num_elems; - struct sof_probe_dma dma[0]; + struct sof_probe_dma dma[]; } __packed;

struct sof_ipc_probe_info_params { @@ -51,19 +51,19 @@ struct sof_ipc_probe_info_params { struct sof_ipc_probe_dma_remove_params { struct sof_ipc_cmd_hdr hdr; unsigned int num_elems; - unsigned int stream_tag[0]; + unsigned int stream_tag[]; } __packed;

struct sof_ipc_probe_point_add_params { struct sof_ipc_cmd_hdr hdr; unsigned int num_elems; - struct sof_probe_point_desc desc[0]; + struct sof_probe_point_desc desc[]; } __packed;

struct sof_ipc_probe_point_remove_params { struct sof_ipc_cmd_hdr hdr; unsigned int num_elems; - unsigned int buffer_id[0]; + unsigned int buffer_id[]; } __packed;

int sof_ipc_probe_init(struct snd_sof_dev *sdev,