Re: [PATCH] kvmtool: Makefile: allow overriding CC and LD

[Andre Przywara <andre.przywara@arm.com>]

Hi Paolo,

On 19/06/15 10:59, Paolo Bonzini wrote:
> 
> 
> On 18/06/2015 17:50, Andre Przywara wrote:
>> Currently we set CC unconditionally to ${CROSS_COMPILE}gcc, the same
>> for LD.
>> Allow people to override the compiler name by specifying it explicitly
>> on the command line or via the environment.
>> Beside calling a certain compiler binary this allows to pass in
>> options to the compiler, which lets us get rid of the PowerPC
>> overrides in the Makefile. Possible uses:
>> $ make CC="gcc -m64" LD="ld -melf64ppc"
>> (build kvmtool on a PowerPC toolchain defaulting to 32-bit)
>> $ make CC="gcc -m32" LD="ld -melf_i386"
>> (build a 32-bit binary on a multilib-enabled x86-64 compiler)
>>
>> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
>> ---
>>  Makefile | 10 ++++++----
>>  1 file changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/Makefile b/Makefile
>> index 6110b8e..888bee5 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -14,9 +14,13 @@ export E Q
>>  include config/utilities.mak
>>  include config/feature-tests.mak
>>  
>> -CC	:= $(CROSS_COMPILE)gcc
>> +ifeq ($(origin CC), default)
>> +	CC	:= $(CROSS_COMPILE)gcc
>> +endif
>>  CFLAGS	:=
>> -LD	:= $(CROSS_COMPILE)ld
>> +ifeq ($(origin LD), default)
>> +	LD	:= $(CROSS_COMPILE)ld
>> +endif
> 
> I know zero about the kvmtool build system, 

Well, it inherits a lot from the kernel ;-)

> but that ought not to be
> necessary.  The make manual says:
> 
> "If a variable has been set with a command argument (*note Overriding
> Variables: Overriding.), then ordinary assignments in the makefile are
> ignored."

Right, there was this nasty difference between "CC=gcc make" and
"make CC=gcc". So I agree that the latter works even without that patch.

Guess I was only looking at the environment here.
Paolo, thanks for pointing out!

Will, please ignore this patch then.

Cheers,
Andre.

> 
> Paolo
> 
>>  LDFLAGS	:=
>>  
>>  FIND	:= find
>> @@ -148,8 +152,6 @@ ifeq ($(ARCH), powerpc)
>>  	OBJS	+= powerpc/spapr_pci.o
>>  	OBJS	+= powerpc/xics.o
>>  	ARCH_INCLUDE := powerpc/include
>> -	CFLAGS 	+= -m64
>> -	LDFLAGS += -m elf64ppc
>>  
>>  	ARCH_WANT_LIBFDT := y
>>  endif
>>
>