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

[Masahiro Yamada]

Hi Detlev,


On Wed, 05 Mar 2014 11:06:03 +0100
Detlev Zundel <dzu at 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 at 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...


Best Regards
Masahiro Yamada