On Sun, Sep 20, 2020 at 12:42:51PM +0900, Masahiro Yamada wrote:

On Sun, Sep 20, 2020 at 4:03 AM Andrew Lunn [off-list ref] wrote:

quoted

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/.

 
It definitely is.

drivers/net:
https://www.spinics.net/lists/netdev/msg683687.html

drivers/spi
https://www.spinics.net/lists/linux-spi/msg23280.html

drivers/mfd
https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg2211644.html

etc.

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.

Do you think this will scale?

Lets just assume we do this at driver/ level. We have 141
subdirectories in driver/ . So we will end up with 141

subdir-ccflags-y += 

lines which we need to maintain.

Given the current cleanup effort, many are going to be identical to
todays W=1.

How do we maintain those 141 lines when it is time to add a new flag
to W=1?

How often are new W=1 flags added? My patch exported
KBUILD_CFLAGS_WARN1. How about instead we export
KBUILD_CFLAGS_WARN1_20200920. A subsystem can then sign up to being
W=1 clean as for the 20200920 definition of W=1.

If you want to add a new warning

KBUILD_CFLAGS_WARN1_20201031 := KBUILD_CFLAGS_WARN1_20200920 + "-Wghosts"

W=1 will always use the latest. You then build with W=1, maybe by
throwing it at 0-day, find which subsystems are still clean, and
update their subdir-ccflags-y += line with the new timestamp?

This should help with scaling, in that a subsystem is not dealing with
a list of warnings, just a symbol that represents the warnings from a
particular date?

Or maybe others have better ideas?

   Andrew