* [PATCH] KVM: selftests: add -MP to CFLAGS
@ 2023-10-28 19:34 David Woodhouse
2023-10-29 21:13 ` David Laight
2023-11-30 1:44 ` Sean Christopherson
0 siblings, 2 replies; 6+ messages in thread
From: David Woodhouse @ 2023-10-28 19:34 UTC (permalink / raw)
To: kvm; +Cc: Paolo Bonzini, Shuah Khan, linux-kselftest, linux-kernel
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From: David Woodhouse <dwmw@amazon.co.uk>
Using -MD without -MP causes build failures when a header file is deleted
or moved. With -MP, the compiler will emit phony targets for the header
files it lists as dependencies, and the Makefiles won't refuse to attempt
to rebuild a C unit which no longer includes the deleted header.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
tools/testing/selftests/kvm/Makefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index a3bb36fb3cfc..20ea549da570 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -211,7 +211,7 @@ else
LINUX_TOOL_ARCH_INCLUDE = $(top_srcdir)/tools/arch/$(ARCH)/include
endif
CFLAGS += -Wall -Wstrict-prototypes -Wuninitialized -O2 -g -std=gnu99 \
- -Wno-gnu-variable-sized-type-not-at-end -MD\
+ -Wno-gnu-variable-sized-type-not-at-end -MD -MP \
-fno-builtin-memcmp -fno-builtin-memcpy -fno-builtin-memset \
-fno-builtin-strnlen \
-fno-stack-protector -fno-PIE -I$(LINUX_TOOL_INCLUDE) \
--
2.41.0
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^ permalink raw reply related [flat|nested] 6+ messages in thread
* RE: [PATCH] KVM: selftests: add -MP to CFLAGS
2023-10-28 19:34 [PATCH] KVM: selftests: add -MP to CFLAGS David Woodhouse
@ 2023-10-29 21:13 ` David Laight
2023-10-30 9:45 ` David Woodhouse
2023-11-30 1:44 ` Sean Christopherson
1 sibling, 1 reply; 6+ messages in thread
From: David Laight @ 2023-10-29 21:13 UTC (permalink / raw)
To: 'David Woodhouse', kvm@vger.kernel.org
Cc: Paolo Bonzini, Shuah Khan, linux-kselftest@vger.kernel.org,
linux-kernel@vger.kernel.org
From: David Woodhouse
> Sent: 28 October 2023 20:35
>
> Using -MD without -MP causes build failures when a header file is deleted
> or moved. With -MP, the compiler will emit phony targets for the header
> files it lists as dependencies, and the Makefiles won't refuse to attempt
> to rebuild a C unit which no longer includes the deleted header.
Won't a phony target stop a header being built if there is
an actual rule to build it?
I usually add:
%.h:
echo "Ignoring stale dependency for $@"
Which only applies if there isn't an explicit rule.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: selftests: add -MP to CFLAGS
2023-10-29 21:13 ` David Laight
@ 2023-10-30 9:45 ` David Woodhouse
2023-10-30 10:08 ` David Laight
0 siblings, 1 reply; 6+ messages in thread
From: David Woodhouse @ 2023-10-30 9:45 UTC (permalink / raw)
To: David Laight, kvm@vger.kernel.org
Cc: Paolo Bonzini, Shuah Khan, linux-kselftest@vger.kernel.org,
linux-kernel@vger.kernel.org
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On Sun, 2023-10-29 at 21:13 +0000, David Laight wrote:
> From: David Woodhouse
> > Sent: 28 October 2023 20:35
> >
> > Using -MD without -MP causes build failures when a header file is deleted
> > or moved. With -MP, the compiler will emit phony targets for the header
> > files it lists as dependencies, and the Makefiles won't refuse to attempt
> > to rebuild a C unit which no longer includes the deleted header.
>
> Won't a phony target stop a header being built if there is
> an actual rule to build it?
It probably would have taken you about the same time to find the answer
for yourself, as it took to write that email. Why don't you try it?
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^ permalink raw reply [flat|nested] 6+ messages in thread
* RE: [PATCH] KVM: selftests: add -MP to CFLAGS
2023-10-30 9:45 ` David Woodhouse
@ 2023-10-30 10:08 ` David Laight
2023-10-30 10:22 ` David Woodhouse
0 siblings, 1 reply; 6+ messages in thread
From: David Laight @ 2023-10-30 10:08 UTC (permalink / raw)
To: 'David Woodhouse', kvm@vger.kernel.org
Cc: Paolo Bonzini, Shuah Khan, linux-kselftest@vger.kernel.org,
linux-kernel@vger.kernel.org
From: David Woodhouse
> Sent: 30 October 2023 09:46
>
> On Sun, 2023-10-29 at 21:13 +0000, David Laight wrote:
> > From: David Woodhouse
> > > Sent: 28 October 2023 20:35
> > >
> > > Using -MD without -MP causes build failures when a header file is deleted
> > > or moved. With -MP, the compiler will emit phony targets for the header
> > > files it lists as dependencies, and the Makefiles won't refuse to attempt
> > > to rebuild a C unit which no longer includes the deleted header.
> >
> > Won't a phony target stop a header being built if there is
> > an actual rule to build it?
>
> It probably would have taken you about the same time to find the answer
> for yourself, as it took to write that email. Why don't you try it?
I was sure that just adding
foo.h:
would generate a 'no rules to build' error.
Maybe that was BSD make or SYS-V make.
But calling the 'phony' is probably wrong.
PHONY has a very specific meaning to make - and these aren't PHONY.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: selftests: add -MP to CFLAGS
2023-10-30 10:08 ` David Laight
@ 2023-10-30 10:22 ` David Woodhouse
0 siblings, 0 replies; 6+ messages in thread
From: David Woodhouse @ 2023-10-30 10:22 UTC (permalink / raw)
To: David Laight, kvm@vger.kernel.org
Cc: Paolo Bonzini, Shuah Khan, linux-kselftest@vger.kernel.org,
linux-kernel@vger.kernel.org
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On Mon, 2023-10-30 at 10:08 +0000, David Laight wrote:
> From: David Woodhouse
> > Sent: 30 October 2023 09:46
> >
> > On Sun, 2023-10-29 at 21:13 +0000, David Laight wrote:
> > > From: David Woodhouse
> > > > Sent: 28 October 2023 20:35
> > > >
> > > > Using -MD without -MP causes build failures when a header file is deleted
> > > > or moved. With -MP, the compiler will emit phony targets for the header
> > > > files it lists as dependencies, and the Makefiles won't refuse to attempt
> > > > to rebuild a C unit which no longer includes the deleted header.
> > >
> > > Won't a phony target stop a header being built if there is
> > > an actual rule to build it?
> >
> > It probably would have taken you about the same time to find the answer
> > for yourself, as it took to write that email. Why don't you try it?
>
> I was sure that just adding
>
> foo.h:
>
> would generate a 'no rules to build' error.
> Maybe that was BSD make or SYS-V make.
>
> But calling the 'phony' is probably wrong.
> PHONY has a very specific meaning to make - and these aren't PHONY.
I recommend filing a bug against the GCC documentation then.
https://gcc.gnu.org/onlinedocs/gcc/Preprocessor-Options.html#index-MP
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: selftests: add -MP to CFLAGS
2023-10-28 19:34 [PATCH] KVM: selftests: add -MP to CFLAGS David Woodhouse
2023-10-29 21:13 ` David Laight
@ 2023-11-30 1:44 ` Sean Christopherson
1 sibling, 0 replies; 6+ messages in thread
From: Sean Christopherson @ 2023-11-30 1:44 UTC (permalink / raw)
To: Sean Christopherson, kvm, David Woodhouse
Cc: Paolo Bonzini, Shuah Khan, linux-kselftest, linux-kernel
On Sat, 28 Oct 2023 20:34:53 +0100, David Woodhouse wrote:
> Using -MD without -MP causes build failures when a header file is deleted
> or moved. With -MP, the compiler will emit phony targets for the header
> files it lists as dependencies, and the Makefiles won't refuse to attempt
> to rebuild a C unit which no longer includes the deleted header.
>
>
Applied to kvm-x86 selftests, thanks!
[1/1] KVM: selftests: add -MP to CFLAGS
https://github.com/kvm-x86/linux/commit/fc6543bb55d4
--
https://github.com/kvm-x86/linux/tree/next
^ permalink raw reply [flat|nested] 6+ messages in thread
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2023-10-28 19:34 [PATCH] KVM: selftests: add -MP to CFLAGS David Woodhouse
2023-10-29 21:13 ` David Laight
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2023-10-30 10:08 ` David Laight
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