Re: [v3] Help wanted for enabling -Wshadow=local

[Thomas Huth <thuth@redhat.com>]

On 06/10/2023 16.45, Markus Armbruster wrote:
> Local variables shadowing other local variables or parameters make the
> code needlessly hard to understand.  Bugs love to hide in such code.
> Evidence: "[PATCH v3 1/7] migration/rdma: Fix save_page method to fail
> on polling error".
> 
> Enabling -Wshadow would prevent bugs like this one.  But we have to
> clean up all the offenders first.
> 
> Quite a few people responded to my calls for help.  Thank you so much!
> 
> I'm collecting patches in my git repo at
> https://repo.or.cz/qemu/armbru.git in branch shadow-next.  All but the
> last two are in a pending pull request.
> 
> My test build is down to seven files with warnings.  "[PATCH v2 0/3]
> hexagon: GETPC() and shadowing fixes" takes care of four, but it needs a
> rebase.
> 
> Remaining three:
> 
>      In file included from ../hw/display/virtio-gpu-virgl.c:19:
>      ../hw/display/virtio-gpu-virgl.c: In function ‘virgl_cmd_submit_3d’:
>      /work/armbru/qemu/include/hw/virtio/virtio-gpu.h:228:16: warning: declaration of ‘s’ shadows a previous local [-Wshadow=compatible-local]
>        228 |         size_t s;                                                       \
>            |                ^
>      ../hw/display/virtio-gpu-virgl.c:215:5: note: in expansion of macro ‘VIRTIO_GPU_FILL_CMD’
>        215 |     VIRTIO_GPU_FILL_CMD(cs);
>            |     ^~~~~~~~~~~~~~~~~~~
>      ../hw/display/virtio-gpu-virgl.c:213:12: note: shadowed declaration is here
>        213 |     size_t s;
>            |            ^
> 
>      In file included from ../contrib/vhost-user-gpu/virgl.h:18,
>                       from ../contrib/vhost-user-gpu/virgl.c:17:
>      ../contrib/vhost-user-gpu/virgl.c: In function ‘virgl_cmd_submit_3d’:
>      ../contrib/vhost-user-gpu/vugpu.h:167:16: warning: declaration of ‘s’ shadows a previous local [-Wshadow=compatible-local]
>        167 |         size_t s;                                               \
>            |                ^
>      ../contrib/vhost-user-gpu/virgl.c:203:5: note: in expansion of macro ‘VUGPU_FILL_CMD’
>        203 |     VUGPU_FILL_CMD(cs);
>            |     ^~~~~~~~~~~~~~
>      ../contrib/vhost-user-gpu/virgl.c:201:12: note: shadowed declaration is here
>        201 |     size_t s;
>            |            ^
> 
>      ../contrib/vhost-user-gpu/vhost-user-gpu.c: In function ‘vg_resource_flush’:
>      ../contrib/vhost-user-gpu/vhost-user-gpu.c:837:29: warning: declaration of ‘i’ shadows a previous local [-Wshadow=local]
>        837 |             pixman_image_t *i =
>            |                             ^
>      ../contrib/vhost-user-gpu/vhost-user-gpu.c:757:9: note: shadowed declaration is here
>        757 |     int i;
>            |         ^
> 
> Gerd, Marc-André, or anybody else?
> 
> More warnings may lurk in code my test build doesn't compile.  Need a
> full CI build with -Wshadow=local to find them.  Anybody care to kick
> one off?

I ran a build here (with -Werror enabled, so that it's easier to see where 
it breaks):

  https://gitlab.com/thuth/qemu/-/pipelines/1028023489

... but I didn't see any additional spots in the logs beside the ones that 
you already listed.

  Thomas