Gustavo A. R. Silva

"The C language allows switch cases to "fall through" when a "break" statement is missing at the end of a case. This, however, introduces ambiguity in the code, as it's not always clear if the missing break is intentional or a bug..." https://www.kernel.org/doc/html/latest/process/deprecated.html#implicit-switch-case-fall-through …

Friday night, casually building ARCH=sh for the first time, I found a 10-year-old bug thanks to -Wimplicit-fallthrough: https://lore.kernel.org/patchwork/patch/1113467/ … This is the perfect way to officially start my weekend. Cheers!

Happy to see other people finding more bugs (this time in ARM64) thanks to -Wimplicit-fallthrough: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3d584a3c85d6fe2cf878f220d4ad7145e7f89218 … This bug was introduced in December 2017. It's fixed in mainline now and will be applied to 4.17+ stable kernels, soon.

This made my day: https://lore.kernel.org/linux-iio/20190813135802.GB27392@kroah.com/ … Mission accomplished. :)

Kernel CI build for yesterday's linux-next (next-20190820): https://lore.kernel.org/linux-next/5d5bd622.1c69fb81.27320.88e2@mx.google.com/ … 70 fall-through warnings. Today's linux-next (next-20190821): https://lore.kernel.org/linux-next/5d5d39eb.1c69fb81.caf30.632c@mx.google.com/ … 0 fall-through warnings on x86_64, i386, arm, arm64, mips, riscv, arc and sh.

And yet another years-old bug is still out there in the wild. Hopefully, the bugfix will make it to mainline and land in stable, soon: https://lore.kernel.org/lkml/20190909052952.GA32131@embeddedor/ … This bug was introduced in 2015. ARCH=powerpc mpc83xx_defconfig

u-boot is about to globally enable -Wimplicit-fallthrough: https://lists.denx.de/pipermail/u-boot/2020-May/411614.html … and that's great news!

I don't think I've documented this fix for a "missing continue" bug in this thread before, so here I go: https://git.kernel.org/linus/2c930e3d0aed1505e86e0928d323df5027817740 … The bug was introduced in August 2014 by commit 65c7843c942d0 ("usbtest: Add interrupt EP testcases"). The bugfix was applied to -stable in 2017.

The bugfix mentioned above was part of a small series: https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1369379.html … https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1369380.html … At the time I was new to kernel development and I wasn't into the good practice of adding the "Fixes:" and "stable" tags to the changelog text.