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?
