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

[Andre Przywara]

On Fri, 28 Mar 2025 11:28:05 +0100
Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:

Hi,

> 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

Ah, didn't know we have that in U-Boot as well! Sounds promising, and
fixes the sandbox build for me (when using bzlib_decompress.o). I will add
this to the last patch and will check what the CI has to say about this.

Thanks for the heads up!

Cheers,
Andre

> 
> 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(-)
> >  
>