Re: [PATCH] block/qcow2-cluster: Add missing "fallthrough" annotation

[Philippe Mathieu-Daudé]

Hi Thomas,

On 9/8/20 9:00 AM, Thomas Huth wrote:
> When compiling with -Werror=implicit-fallthrough, the compiler currently
> complains:

Do you know what is missing to add this in configure::warn_flags?

> 
> ../../devel/qemu/block/qcow2-cluster.c: In function ‘cluster_needs_new_alloc’:
> ../../devel/qemu/block/qcow2-cluster.c:1320:12: error: this statement may fall
>  through [-Werror=implicit-fallthrough=]
>          if (l2_entry & QCOW_OFLAG_COPIED) {
>             ^
> ../../devel/qemu/block/qcow2-cluster.c:1323:5: note: here
>      case QCOW2_CLUSTER_UNALLOCATED:
>      ^~~~
> 
> It's quite obvious that the fallthrough is intended here, so let's add
> a comment to silence the compiler warning.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  block/qcow2-cluster.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
> index 996b3314f4..fcdf7af8e6 100644
> --- a/block/qcow2-cluster.c
> +++ b/block/qcow2-cluster.c
> @@ -1320,6 +1320,7 @@ static bool cluster_needs_new_alloc(BlockDriverState 
> *bs, uint64_t l2_entry)
>          if (l2_entry & QCOW_OFLAG_COPIED) {
>              return false;
>          }
> +        /* fallthrough */
>      case QCOW2_CLUSTER_UNALLOCATED:
>      case QCOW2_CLUSTER_COMPRESSED:
>      case QCOW2_CLUSTER_ZERO_PLAIN:
>