linux-kernel - Re: [PATCH trace-cmd 3/3] Revert "trace-cmd: Use conditional assignment of CC and AR"

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Message-ID: <4D783038.8080103@linux.intel.com>
Date:	Wed, 09 Mar 2011 17:58:16 -0800
From:	Darren Hart <dvhart@...ux.intel.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	David Sharp <dhsharp@...gle.com>, linux-kernel@...r.kernel.org,
	mrubin@...gle.com
Subject: Re: [PATCH trace-cmd 3/3] Revert "trace-cmd: Use conditional assignment
 of CC and AR"

On 03/09/2011 05:36 PM, Steven Rostedt wrote:
> On Wed, 2011-03-09 at 17:27 -0800, Darren Hart wrote:
>> On 03/09/2011 03:58 PM, David Sharp wrote:
>>> This reverts commit 6c696cec3f264a9399241b6e648f58bc97117d49.
>>>
>>> Make has default values CC and AR of 'cc' and 'ar' respectively. This means
>>> that "CC ?= anything" will never have effect, because CC is always already set.
>>> Because of this, 6c696cec makes setting CROSS_COMPILE from the command line or
>>> environment useless.
>>
>> The problem with this approach is it prevents the user from setting CC
>> explicitly with the environment which is a very common way of using a
>> specific version of gcc (for example). It also places restrictions on
>> the filename of the compiler (it must end in gcc - so gcc-4.5.1 cannot
>> work), this isn't acceptable.
>>
>> You could use CC=your-cross-compiler, and if that doesn't work for you,
>> you could prepare a patch that conditionally sets CC only if
>> CROSS_COMPILE is set, but please do not simply revert this patch which
>> solved a real problem with the Makefile.
>
> Hmm, but the thing is, the change did not work,

It did work for me as I was setting CC= on the command line.

unless your environment
> for some reason does not supply a 'cc'. Or that 'cc' defaulted to the
> compiler that you wanted, where 'gcc' would not.
>
> Thus, would you be fine with something like:
>
> 	BUILD_CC ?=	$(CROSS_COMPILE)gcc
> 	CC	 =	$(BUILD_CC)

This would also work, but what is wrong with:

dvhart@...bt:templates$ cat Makefile
ifdef CROSS_COMPILE
CC = $(CROSS_COMPILE)gcc
AR = $(CROSS_COMPILE)ar
endif

all:
	echo "CC: $(CC)"

dvhart@...bt:templates$ make -s
CC: cc

dvhart@...bt:templates$ CC=gcc-4.5.1 make -s
CC: gcc-4.5.1

dvhart@...bt:templates$ CROSS_COMPILE=my-cross- make -s
CC: my-cross-gcc


Seems to meet everyone's needs without changing any tools/scripts/etc 
that have used trace-cmd before or after the CC ?= wreckage.



Thanks,

--
Darren

>
> Then you could just update BUILD_CC and that will update CC for you.
>
> -- Steve
>
>


-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel
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