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

[Thomas Huth <thuth@redhat.com>]

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.

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

 Thanks,
  Thomas