linux-kernel - Re: [PATCH 1/3] selftests: ublk: kublk: build with -Werror iff CONFIG

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Message-ID: <aBFWtvHv84aPTMvi@dev-ushankar.dev.purestorage.com>
Date: Tue, 29 Apr 2025 16:46:14 -0600
From: Uday Shankar <ushankar@...estorage.com>
To: Ming Lei <ming.lei@...hat.com>
Cc: Shuah Khan <shuah@...nel.org>, linux-block@...r.kernel.org,
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] selftests: ublk: kublk: build with -Werror iff
 CONFIG_WERROR=y

On Tue, Apr 29, 2025 at 09:11:05AM +0800, Ming Lei wrote:
> On Mon, Apr 28, 2025 at 05:10:20PM -0600, Uday Shankar wrote:
> > Compiler warnings can catch bugs at compile time. They can also produce
> > annoying false positives. Due to this duality, the kernel provides
> > CONFIG_WERROR so that the developer can choose whether or not they want
> > compiler warnings to fail the build. Use this same config options to
> > control whether or not warnings in building kublk fail its build.
> > 
> > Signed-off-by: Uday Shankar <ushankar@...estorage.com>
> > ---
> >  tools/testing/selftests/ublk/Makefile | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/testing/selftests/ublk/Makefile b/tools/testing/selftests/ublk/Makefile
> > index ec4624a283bce2ebeed80509be6573c1b7a3623d..86474cfe8d03b2df3f8c9bc1a5902701a0f72f58 100644
> > --- a/tools/testing/selftests/ublk/Makefile
> > +++ b/tools/testing/selftests/ublk/Makefile
> > @@ -1,6 +1,8 @@
> >  # SPDX-License-Identifier: GPL-2.0
> >  
> > -CFLAGS += -O3 -Wl,-no-as-needed -Wall -I $(top_srcdir)
> > +CONFIG = $(top_srcdir)/include/config/auto.conf
> > +WERROR = $(if $(shell grep CONFIG_WERROR=y ${CONFIG}),-Werror,)
> > +CFLAGS += -O3 -Wl,-no-as-needed -Wall ${WERROR} -I $(top_srcdir)
> >  LDLIBS += -lpthread -lm -luring
> 
> I think it isn't good to reuse kernel CONFIG_WERROR for test code.
> 
> But it can be done in the following way by passing 'WERROR=1' to make
> command line:
> 
> +ifneq ($(WERROR),0)
> +       CFLAGS += -Werror
> +endif

I've taken this approach in [1]. It actually passes -Werror by default,
but it gives the developer a way to disable it with

make WERROR=0 TARGETS=ublk kselftest

[1] https://lore.kernel.org/linux-block/20250429-ublk_selftests-v2-1-e970b6d9e4f4@purestorage.com/