On Sun, Sep 20, 2020 at 4:03 AM Andrew Lunn <andrew@xxxxxxx> wrote: > > There is a movement to make the code base compile clean with W=1. Some > subsystems are already clean. In order to keep them clean, we need > developers to build new code with W=1 by default in these subsystems. > > This patchset refactors the core Makefile warning code to allow the > additional warnings W=1 adds available to any Makefile. The Ethernet > PHY subsystem Makefiles then make use of this to make W=1 the default > for this subsystem. > > RFT since i've only tested with x86 and arm with a modern gcc. Is the > code really clean for older compilers? For clang? I appreciate your efforts for keeping your subsystems clean for W=1 builds, and I hope this work will be extended towards upper directory level, drivers/net/phy -> drivers/net -> drivers/. However, when we talk about W=1, we consider not only the current option set in W=1, but also options that might be added by future compilers because every GCC/Clang release adds new warning options. Let's say, the future release, GCC 14 would add a new option -Wfoo-bar, which is reasonable enough to be enabled by default, but doing so would emit a lot of warnings in the current kernel tree. We cannot add -Wfoo-bar to W=0 right away, because our general consensus is that the normal build should be warning-free. In the current routine, we add -Wfoo-bar to W=1 with hope we can gradually fix the code and eventually migrate it to W=0. It is not always easy to move W=1 options to W=0 when we have lots of code fixed. At least, 0-day bot iterates compile tests with W=1, so new code violating -Wfoo-bar would be blocked. With this patch series applied, where should we add -Wfoo-bar? Adding it to W=1 would emit warnings under drivers/net/ since W=1 is now the default for the net subsystem. Do we require to fix the code under driver/net/ first? Or, should we add it to W=2 temporarily, then move it to W=1 once we fix drivers/net/? So, another idea might be hard-coding extra warnings like drivers/gpu/drm/i915/Makefile. For example, your subsystem already achieved -Wmissing-declarations free. You can add subdir-ccflags-y += -Wmissing-declarations to drivers/net/phy/Makefile. Once you fix all net drivers, you can move it to the parent, drivers/net/Makefile. Then, drivers/Makefile next, and if it reaches the top directory level, we can move it to W=0. Some W=1 options stay there just because we cannot fix lots of code. So, our code should be improved with regard to W=1 warnings, but we might need some clarification about how to do it gradually. Comments are appreciated. > Andrew Lunn (2): > scripts: Makefile.extrawarn: Add W=1 warnings to a symbol > net: phylib: Enable W=1 by default > > drivers/net/mdio/Makefile | 3 +++ > drivers/net/pcs/Makefile | 3 +++ > drivers/net/phy/Makefile | 3 +++ > scripts/Makefile.extrawarn | 33 ++++++++++++++++++--------------- > 4 files changed, 27 insertions(+), 15 deletions(-) > > -- > 2.28.0 > -- Best Regards Masahiro Yamada
