[PATCH 00/18] Annotate switch/case fallthrough cases

[Heinrich Schuchardt]

On 27.03.25 16:32, Andre Przywara wrote:
> C's implicit fallthrough behaviour in switch/case statements can lead to
> subtle bugs. Quite some while ago many compilers introduced warnings in
> those cases, requiring intentional fallthrough's to be annotated.
>
> So far we were not enabling that compiler option, so many ambiguities
> and some bugs in the code went unnoticed.
>
> This series adds the required annotations in code paths that the first
> stage of the U-Boot CI covers. There is a large number of cases left
> in the libbz2 code. The usage of switch/case is borderline insane there,
> labels are hidden in macros, and there are no breaks, but just goto's.
> Upstream still uses very similar code, without any annotations. I still
> am not 100% sure those are meant to fall through or not, and plan to do
> further investigations, but didn't want to hold the rest of the patches
> back. You can see for yourself by applying patch 18/18 and building for
> sandbox64, for instance.

Can we use something like

CFLAGS_REMOVE_bzlib.o = -Wimplicit-fallthrough

in the Makefile if that module is too hard to fix?

Best regards

Heinrich

>
> Because of this we cannot quite enable the warning in the Makefile yet,
> but those fixes are worth regardless, and be it to increase readability.
>
> Please not that those patches do not fix anything, really, they just add
> those fallthrough annotations, so the series is not really critical.
>
> Cheers,
> Andre
>
> Andre Przywara (18):
>    spl: mmc: properly annotate fallthrough
>    zlib: annotate switch/case fallthrough cases
>    gadget: f_thor: annotate switch/case fallthrough
>    use proper fallthrough annotations
>    net/net: fix switch/case fallthrough annotations
>    fastboot: annotate switch/case fallthrough case
>    net: sun8i-emac: annotate fallthrough
>    usb: ohci-hcd: annotate switch/case fallthrough
>    usb: xhci: annotate switch/case fallthrough properly (TBF)
>    video: annotate switch/case fall-through
>    net: e1000: annotate switch/case fallthrough
>    mtd: ubi: annotate fallthrough (TBF)
>    arm: mach-k3: am62p: annotate switch/case fallthrough
>    mtd: spi-nor-tiny: annotate switch/case fallthrough
>    mtd: rawnand: nand_base: annotate switch/case fallthrough
>    cmd: pmic: annotate switch/case fallthrough
>    cmd: spl: annotate switch/case fallthrough
>    [DO NOT MERGE] Makefile: enable switch/case fallthrough warnings
>
>   Makefile                              |  1 +
>   arch/arm/mach-k3/am62px/am62p5_init.c |  1 +
>   cmd/pmic.c                            |  1 +
>   cmd/spl.c                             |  2 ++
>   common/command.c                      |  2 +-
>   common/spl/spl_mmc.c                  |  1 +
>   drivers/fastboot/fb_command.c         |  1 +
>   drivers/mtd/nand/raw/nand_base.c      |  4 ++++
>   drivers/mtd/spi/spi-nor-tiny.c        |  1 +
>   drivers/mtd/ubi/attach.c              |  1 +
>   drivers/mtd/ubi/build.c               |  3 +++
>   drivers/net/e1000.c                   |  2 ++
>   drivers/net/sun8i_emac.c              |  1 +
>   drivers/usb/gadget/f_thor.c           |  1 +
>   drivers/usb/host/ohci-hcd.c           |  3 ++-
>   drivers/usb/host/xhci.c               |  2 +-
>   drivers/video/video-uclass.c          |  2 ++
>   lib/tiny-printf.c                     |  2 +-
>   lib/zlib/inflate.c                    | 21 +++++++++++++++++++++
>   net/net.c                             |  5 ++---
>   20 files changed, 50 insertions(+), 7 deletions(-)
>