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

[Thomas Huth <thuth@redhat.com>]

On 06/10/2023 18.18, Thomas Huth wrote:
> 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.

After adding two more patches to fix the above warnings, things look pretty 
good:

  https://gitlab.com/thuth/qemu/-/pipelines/1028413030

There are just some warnings left in the BSD code, as Warner already 
mentioned in his reply to v2 of your mail:

  https://gitlab.com/thuth/qemu/-/jobs/5241420713

  Thomas