Re: [kvm-unit-tests PATCH 1/7] x86: Makefile: Allow division on x86_64-elf binutils

[Roman Bolshakov <r.bolshakov@yadro.com>]

On Fri, Aug 28, 2020 at 07:00:19AM +0200, Thomas Huth wrote:
> On 10/08/2020 15.06, Roman Bolshakov wrote:
> > For compatibility with other SVR4 assemblers, '/' starts a comment on
> > *-elf binutils target and thus division operator is not allowed [1][2].
> > That breaks cstart64.S build:
> > 
> >   x86/cstart64.S: Assembler messages:
> >   x86/cstart64.S:294: Error: unbalanced parenthesis in operand 1.
> > 
> > The option is ignored on the Linux target of GNU binutils.
> > 
> > 1. https://sourceware.org/binutils/docs/as/i386_002dChars.html
> > 2. https://sourceware.org/binutils/docs/as/i386_002dOptions.html#index-_002d_002ddivide-option_002c-i386
> > 
> > Cc: Cameron Esfahani <dirty@apple.com>
> > Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
> > ---
> >  x86/Makefile | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/x86/Makefile b/x86/Makefile
> > index 8a007ab..22afbb9 100644
> > --- a/x86/Makefile
> > +++ b/x86/Makefile
> > @@ -1 +1,3 @@
> >  include $(SRCDIR)/$(TEST_DIR)/Makefile.$(ARCH)
> > +
> > +COMMON_CFLAGS += -Wa,--divide
> 
> Some weeks ago, I also played with an elf cross compiler and came to the
> same conclusion, that we need this option there. Unfortunately, it does
> not work with clang:
> 
>  https://gitlab.com/huth/kvm-unit-tests/-/jobs/707986800#L1629
> 
> You could try to wrap it with "cc-option" instead ... or use a proper
> check in the configure script to detect whether it's needed or not.
> 

Hi Thomas,

Thanks for reviewing the series. I'll look into both options and will
test with both gcc and clang afterwards. I can also update .travis.yml
in a new patch to test the build on macOS.

> And can you please put it next to the other COMMON_CFLAGS in
> x86/Makefile.common instead of x86/Makefile?
> 

Sure.

Regards,
Roman