Re: Help wanted for enabling -Wshadow=local

[Daniel Henrique Barboza]

Markus,

I found these libvhost-user errors when trying to compile riscv64-linux-user 
with -Wshadow=local.
I don't see it mentioned in the email so I decided to chime in:


-user.c.o -c ../subprojects/libvhost-user/libvhost-user.c
../subprojects/libvhost-user/libvhost-user.c: In function ‘vu_rem_mem_reg’:
../subprojects/libvhost-user/libvhost-user.c:871:19: error: declaration of ‘m’ 
shadows a previous local [-Werror=shadow=local]
  871 |             void *m = (void *) (uintptr_t) r->mmap_addr;
      |                   ^
../subprojects/libvhost-user/libvhost-user.c:839:27: note: shadowed declaration 
is here
  839 |     VhostUserMemoryRegion m = vmsg->payload.memreg.region, *msg_region = 
&m;
      |                           ^
../subprojects/libvhost-user/libvhost-user.c: In function 
‘vu_set_mem_table_exec’:
../subprojects/libvhost-user/libvhost-user.c:988:15: error: declaration of ‘m’ 
shadows a previous local [-Werror=shadow=local]
  988 |         void *m = (void *) (uintptr_t) r->mmap_addr;
      |               ^
../subprojects/libvhost-user/libvhost-user.c:984:21: note: shadowed declaration 
is here
  984 |     VhostUserMemory m = vmsg->payload.memory, *memory = &m;
      |                     ^
cc1: all warnings being treated as errors


MAINTAINERS file reports that vhost is mister Tsirkin's turf. He's already in 
CC.


Thanks,

Daniel


see the file mentioned in your email so I decided it's better to let you know.

On 9/22/23 06:37, Markus Armbruster wrote:
> If you are in To:, we need your help to enable -Wshadow=local.
>
> 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.
>
> I collected the patches posted so far:
>
>      [PATCH v3 0/7] Steps towards enabling -Wshadow=local
>      Message-ID: <20230921121312.1301864-1-armbru@redhat.com>
>
>      [PATCH v2 00/22] (few more) Steps towards enabling -Wshadow
>      Message-ID: <20230904161235.84651-1-philmd@linaro.org>
>
>      [PATCH 0/3] (few more) Steps towards enabling -Wshadow [3 more]
>      Message-ID: <20230904162824.85385-1-philmd@linaro.org>
>
>      [PATCH 0/8] ppc: Clean up local variable shadowing
>      Message-ID: <20230918145850.241074-1-clg@kaod.org>
>
> Thanks, Philippe & Cedric!
>
> In my local build with -Wshadow=local, warnings remain in just 56 files.
>
> Sorted by subsystems, files covered by multiple subsystems marked
> "(*NUMBER*)", files not covered in MAINTAINERS marked (*guess*):
>
> Guest CPU cores (TCG)
> ---------------------
> ARM TCG CPUs
> M: Peter Maydell <peter.maydell@linaro.org>
>      hw/arm/smmuv3-internal.h(*2*)
>      hw/arm/smmuv3.c(*2*)
>
> ARM SMMU
> M: Eric Auger <eric.auger@redhat.com>
>      hw/arm/smmuv3-internal.h(*2*)
>      hw/arm/smmuv3.c(*2*)
>
> Hexagon TCG CPUs
> M: Brian Cain <bcain@quicinc.com>
>      target/hexagon/gen_helper_funcs.py
>      target/hexagon/mmvec/macros.h
>      target/hexagon/op_helper.c
>      target/hexagon/translate.c
>
> M68K TCG CPUs
> M: Laurent Vivier <laurent@vivier.eu>
>      disas/m68k.c
>
> PowerPC TCG CPUs
> M: Nicholas Piggin <npiggin@gmail.com>
> M: Daniel Henrique Barboza <danielhb413@gmail.com>
> R: Cédric Le Goater <clg@kaod.org>
>      target/ppc/int_helper.c
>
> RISC-V TCG CPUs
>      hw/riscv/opentitan.c(*2*)
>      target/riscv/cpu.c
>      target/riscv/vector_helper.c
>
> X86 TCG CPUs
> M: Paolo Bonzini <pbonzini@redhat.com>
> M: Richard Henderson <richard.henderson@linaro.org>
> M: Eduardo Habkost <eduardo@habkost.net>
>      hw/i386/acpi-build.c(*3*)
>      hw/i386/acpi-microvm.c(*2*)
>      hw/i386/intel_iommu.c(*3*)
>      hw/i386/pc.c(*2*)
>      hw/i386/x86.c(*2*)
>      target/i386/cpu.c(*guess*)
>      target/i386/tcg/seg_helper.c
>      target/i386/tcg/sysemu/svm_helper.c
>      target/i386/tcg/translate.c
>
> Guest CPU Cores (KVM)
> ---------------------
> X86 KVM CPUs
> M: Paolo Bonzini <pbonzini@redhat.com>
> M: Marcelo Tosatti <mtosatti@redhat.com>
>      target/i386/kvm/kvm.c
>
> ARM Machines
> ------------
> ARM cores
> M: Peter Maydell <peter.maydell@linaro.org>
>      hw/intc/arm_gicv3_its.c
>
> Versatile PB
> M: Peter Maydell <peter.maydell@linaro.org>
>      hw/misc/arm_sysctl.c
>
> ASPEED BMCs
> M: Cédric Le Goater <clg@kaod.org>
> M: Peter Maydell <peter.maydell@linaro.org>
> R: Andrew Jeffery <andrew@aj.id.au>
> R: Joel Stanley <joel@jms.id.au>
>      hw/i2c/aspeed_i2c.c
>      hw/misc/aspeed_i3c.c
>
> LoongArch Machines
> ------------------
> Virt
> M: Xiaojuan Yang <yangxiaojuan@loongson.cn>
> M: Song Gao <gaosong@loongson.cn>
>      hw/loongarch/virt.c
>
> RISC-V Machines
> ---------------
> OpenTitan
> M: Alistair Francis <Alistair.Francis@wdc.com>
>      hw/riscv/opentitan.c(*2*)
>
> X86 Machines
> ------------
> PC
> M: Michael S. Tsirkin <mst@redhat.com>
> M: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
>      hw/i386/acpi-build.c(*3*)
>      hw/i386/acpi-microvm.c(*2*)
>      hw/i386/intel_iommu.c(*3*)
>      hw/i386/pc.c(*2*)
>      hw/i386/x86.c(*2*)
>
> PC Chipset
> M: Michael S. Tsirkin <mst@redhat.com>
> M: Paolo Bonzini <pbonzini@redhat.com>
>      hw/i2c/pm_smbus.c
>
> Devices
> -------
> ACPI/SMBIOS
> M: Michael S. Tsirkin <mst@redhat.com>
> M: Igor Mammedov <imammedo@redhat.com>
> R: Ani Sinha <anisinha@redhat.com>
>      hw/acpi/cpu_hotplug.c
>      hw/i386/acpi-build.c(*3*)
>      hw/smbios/smbios.c
>
> Network devices
> M: Jason Wang <jasowang@redhat.com>
>      hw/net/vhost_net.c(*2*)
>
> SCSI
> M: Paolo Bonzini <pbonzini@redhat.com>
> R: Fam Zheng <fam@euphon.net>
>      hw/scsi/mptsas.c
>
> USB
> M: Gerd Hoffmann <kraxel@redhat.com>
>      hw/usb/desc.c
>      hw/usb/dev-hub.c
>      hw/usb/dev-storage.c
>      hw/usb/hcd-xhci.c
>      hw/usb/host-libusb.c
>
> vhost
> M: Michael S. Tsirkin <mst@redhat.com>
>      contrib/vhost-user-gpu/vhost-user-gpu.c(*2*)
>      contrib/vhost-user-gpu/vugpu.h(*2*)
>      hw/net/vhost_net.c(*2*)
>      hw/virtio/vhost.c
>
> virtio
> M: Michael S. Tsirkin <mst@redhat.com>
>      hw/virtio/virtio-pci.c
>      include/hw/virtio/virtio-gpu.h(*2*)
>
> nvme
> M: Keith Busch <kbusch@kernel.org>
> M: Klaus Jensen <its@irrelevant.dk>
>      hw/nvme/ns.c
>
> virtio-gpu
> M: Gerd Hoffmann <kraxel@redhat.com>
>      include/hw/virtio/virtio-gpu.h(*2*)
>
> vhost-user-gpu
> M: Marc-André Lureau <marcandre.lureau@redhat.com>
> R: Gerd Hoffmann <kraxel@redhat.com>
>      contrib/vhost-user-gpu/vhost-user-gpu.c(*2*)
>      contrib/vhost-user-gpu/vugpu.h(*2*)
>
> Subsystems
> ----------
> Overall Audio backends
> M: Gerd Hoffmann <kraxel@redhat.com>
> M: Marc-André Lureau <marcandre.lureau@redhat.com>
>      audio/audio.c
>
> Open Sound System (OSS) Audio backend
> M: Gerd Hoffmann <kraxel@redhat.com>
>      audio/ossaudio.c
>
> Compute Express Link
> M: Jonathan Cameron <jonathan.cameron@huawei.com>
> R: Fan Ni <fan.ni@samsung.com>
>      include/hw/cxl/cxl_device.h
>
> Device Tree
> M: Alistair Francis <alistair.francis@wdc.com>
> R: David Gibson <david@gibson.dropbear.id.au>
>      softmmu/device_tree.c
>
> Dump
> M: Marc-André Lureau <marcandre.lureau@redhat.com>
>      dump/dump.c
>
> Main loop
> M: Paolo Bonzini <pbonzini@redhat.com>
>      softmmu/vl.c
>
> qtest
> M: Thomas Huth <thuth@redhat.com>
> M: Laurent Vivier <lvivier@redhat.com>
> R: Paolo Bonzini <pbonzini@redhat.com>
>      tests/qtest/m48t59-test.c
>
> Seccomp
> M: Daniel P. Berrange <berrange@redhat.com>
>      softmmu/qemu-seccomp.c
>
> Cryptography
> M: Daniel P. Berrange <berrange@redhat.com>
>      crypto/tls-cipher-suites.c
>
> Throttling infrastructure
> M: Alberto Garcia <berto@igalia.com>
>      tests/unit/test-throttle.c
>
> VT-d Emulation
> M: Michael S. Tsirkin <mst@redhat.com>
> M: Peter Xu <peterx@redhat.com>
> R: Jason Wang <jasowang@redhat.com>
>      hw/i386/intel_iommu.c(*3*)
>
> Usermode Emulation
> ------------------
> Linux user
> M: Laurent Vivier <laurent@vivier.eu>
>      linux-user/flatload.c
>      linux-user/mmap.c
>      linux-user/syscall.c
>
> Block drivers
> -------------
> Network Block Device (NBD)
> M: Eric Blake <eblake@redhat.com>
> M: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
>      qemu-nbd.c