[U-Boot] [RFC PATCH] kbuild: use "cc-cross-prefix" to choose CROSS_COMPILE

[Detlev Zundel <dzu@denx.de>]

Hi Masahiro,

> Hi Detlev,
>
>
> On Wed, 05 Mar 2014 11:06:03 +0100
> Detlev Zundel <dzu@denx.de> wrote:
>
>> Hi Masahiro,
>> 
>> > CROSS_COMPILE is generally passed from the command line
>> > or by the environment variable because cross tools
>> > vary from user to user.
>> >
>> > But, having some choices of often used CROSS_COMPILE
>> > seems reasonable.
>> >
>> > $(call cc-cross-prefix, ...) returns the first prefix
>> > where a prefix$(CC) is found in PATH.
>> >
>> > If your cross tools exist in the argument of
>> > $(call cc-cross-prefix, ...), you do not have to
>> > specify it explicitly.
>> >
>> > Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
>> 
>> I have to admit that I don't really like this approach.  On the one hand
>> it is an heuristic trying to guess the intentions of the user.  This is
>> nice if it works but can be very surprising when it goes wrong.
>> 
>> But more imprtantly, it will blur the the boundaries of the build
>> process as we trade the very self contained determinism of "use what
>> CROSS_COMPILE" says to "use what we may find in the rest of the system".
>> 
>> It would even be possible that a "once working" build process will not
>> work anymore because the user has installed a new toolchain in the
>> meantime and then this completely unrelated action has an (unwanted)
>> impact.
>> 
>> In short, I would rather want to stay with our current (clearly defined)
>> setup :)
>> 
>
> Maybe this is verbose, but
> just in case, let me add a few words.
>
> If you like, you can still pass CROSS_COMPILE from the command line
> or by the environment variable.
>
>
>   ifeq ($(CROSS_COMPILE),)
>   CROSS_COMPILE := $(call cc-cross-prefix, arm-linux- arm-linux-gnueabi-)
>   endif
>
> $(call cc-cross-prefix, ...) is invoked only when $(CROSS_COMPILE) is
> empty,
> that is CROSS_COMPILE is not explicitely specified.
>
>
> For users who know everything happening in the built system,
> this patch might be helpful for less typing...

Yes, I fully understand your intention but I still believe that setting
CROSS_COMPILE is usually scripted anyway so the savings are near
negligible and the "price" we pay is adding (more) information about
cross-toolchains which is really outside of the scope of U-Boot (or any
other project I'd say).

If there would be real savings, then maybe it is worth to break the
principle of modularity but in the current discussion I just don't see
that.

Best wishes
  Detlev

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