[Skiboot] [PATCH] external: Fix cross compilation issue

[oliver]

On Thu, Jul 28, 2016 at 8:40 PM, Patrick Williams <patrick at stwcx.xyz> wrote:
> On Thu, Jul 28, 2016 at 03:05:38PM +0530, Vasant Hegde wrote:
>> For some reason Makefile thinks compiler variables like CC is already
>> assigned and ignores CROSS_COMPILE flags. Hence I'm not able to generate
>> arm binary on x86.
>>
>> Use default assignment operator instead of conditional assignment
>> operator (?=) in Makefile.
>>
>> Fixes: 3137d249 (pflash: Allow building under yocto.)
>> CC: Patrick Williams <patrick at stwcx.xyz>
>> CC: Stewart Smith <stewart at linux.vnet.ibm.com>
>> Signed-off-by: Vasant Hegde <hegdevasant at linux.vnet.ibm.com>
>> ---
>>  external/common/rules.mk | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/external/common/rules.mk b/external/common/rules.mk
>> index bb12fd5..416a40d 100644
>> --- a/external/common/rules.mk
>> +++ b/external/common/rules.mk
>> @@ -1,5 +1,5 @@
>> -CC ?= $(CROSS_COMPILE)gcc
>> -LD ?= $(CROSS_COMPILE)ld
>> +CC = $(CROSS_COMPILE)gcc
>> +LD = $(CROSS_COMPILE)ld
>
> This effectively undoes the change I made in 3137d249, so I'm not sure
> why we would want it or why it is needed.

make automatically defines CC so the ?= assignment is never done. You
can get the desired
behaviour with and ifdef block though:

diff --git a/external/common/rules.mk b/external/common/rules.mk
index 5558cd3..4dd7942 100644
--- a/external/common/rules.mk
+++ b/external/common/rules.mk
@@ -1,5 +1,8 @@
-CC ?= $(CROSS_COMPILE)gcc
-LD ?= $(CROSS_COMPILE)ld
+ifdef CROSS_COMPILE
+CC = $(CROSS_COMPILE)gcc
+LD = $(CROSS_COMPILE)ld
+endif
+
 ARCH := $(shell $(GET_ARCH) "$(CROSS_COMPILE)")

 ifeq ($(ARCH),ARCH_ARM)


> Yocto sets CC and LD directly and actually adds some of the CFLAGS onto
> the CC variable (for right or wrong).  Thus it doesn't use CROSS_COMPILE
> directly.  Also, by forcing 'CC = $(CROSS_COMPILE)gcc' we preclude the
> use of clang.

Forcing the assignment is a bad idea, but keep in mind that most of us
aren't using
Yocto. I hit this problem while trying to build a copy of pflash for
an unopened BMC
and needed to use their toolchain. Manually setting CC/LD from the command line
works, but the external/ tools should respect CROSS_COMPILE for consistency with
skiboot itself and linux.

>
>>  ARCH := $(shell $(GET_ARCH) "$(CROSS_COMPILE)")
>>
>>  ifeq ($(ARCH),ARCH_ARM)
>> --
>> 2.5.5
>>
>
> --
> Patrick Williams
>
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