Re: [PATCH] hw/virtio/virtio-gpu: Fix compiler warning when compiling with -Wshadow

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Oct 06, 2023 at 06:45:08PM +0200, Thomas Huth wrote:
> Avoid using trivial variable names in macros, otherwise we get
> the following compiler warning when compiling with -Wshadow=local:
> 
> In file included from ../../qemu/hw/display/virtio-gpu-virgl.c:19:
> ../../home/thuth/devel/qemu/hw/display/virtio-gpu-virgl.c:
>  In function ‘virgl_cmd_submit_3d’:
> ../../qemu/include/hw/virtio/virtio-gpu.h:228:16: error: declaration of ‘s’
>  shadows a previous local [-Werror=shadow=compatible-local]
>   228 |         size_t s;
>       |                ^
> ../../qemu/hw/display/virtio-gpu-virgl.c:215:5: note: in expansion of macro
>  ‘VIRTIO_GPU_FILL_CMD’
>   215 |     VIRTIO_GPU_FILL_CMD(cs);
>       |     ^~~~~~~~~~~~~~~~~~~
> ../../qemu/hw/display/virtio-gpu-virgl.c:213:12: note: shadowed declaration
>  is here
>   213 |     size_t s;
>       |            ^
> cc1: all warnings being treated as errors
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  include/hw/virtio/virtio-gpu.h | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/include/hw/virtio/virtio-gpu.h b/include/hw/virtio/virtio-gpu.h
> index 390c4642b8..8b7e3faf01 100644
> --- a/include/hw/virtio/virtio-gpu.h
> +++ b/include/hw/virtio/virtio-gpu.h
> @@ -225,13 +225,13 @@ struct VhostUserGPU {
>  };
>  
>  #define VIRTIO_GPU_FILL_CMD(out) do {                                   \
> -        size_t s;                                                       \
> -        s = iov_to_buf(cmd->elem.out_sg, cmd->elem.out_num, 0,          \
> +        size_t s_;                                                      \
> +        s_ = iov_to_buf(cmd->elem.out_sg, cmd->elem.out_num, 0,         \
>                         &out, sizeof(out));                              \
> -        if (s != sizeof(out)) {                                         \
> +        if (s_ != sizeof(out)) {                                        \
>              qemu_log_mask(LOG_GUEST_ERROR,                              \
>                            "%s: command size incorrect %zu vs %zu\n",    \
> -                          __func__, s, sizeof(out));                    \
> +                          __func__, s_, sizeof(out));                   \
>              return;                                                     \
>          }                                                               \
>      } while (0)

This is not really enough I think. Someone might
use another macro as parameter to this macro and we'll get
a mess. We want something that's specific to this macro.
How about VIRTIO_GPU_FILL_CMD_s ?


> -- 
> 2.41.0