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Re: CROSS_COMPILE in environment variable

To: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Subject: Re: CROSS_COMPILE in environment variable
From: Geoff Levand <geoffrey.levand@am.sony.com>
Date: Tue, 25 Apr 2006 11:32:46 -0700
Cc: linux-mips@linux-mips.org
In-reply-to: <20060425.133944.88701465.nemoto@toshiba-tops.co.jp>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20060425.133944.88701465.nemoto@toshiba-tops.co.jp>
Sender: linux-mips-bounce@linux-mips.org
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Atsushi Nemoto wrote:
> In the toplevel Makefile, CROSS_COMPILE is described as:
> 
> # CROSS_COMPILE can be set on the command line
> # make CROSS_COMPILE=ia64-linux-
> # Alternatively CROSS_COMPILE can be set in the environment.
> # Default value for CROSS_COMPILE is not to prefix executables
> # Note: Some architectures assign CROSS_COMPILE in their arch/*/Makefile
> 
> And currently, arch/mips/Makefile assigns CROSS_COMPILE as:
> 
> CROSS_COMPILE         := $(tool-prefix)
> 
> This overrides environment variable's settings unconditionaly so we
> can no do the 'alternative' method described above (specify
> CROSS_COMPILE by shell environment variable).
> 
> If arch/mips/Makefile used "?=" assigment instead of ":=", we can
> specify CROSS_COMPILE by shell environment variable.
> 
> Is there any reason to using ":=" ?  If no, shouldn't we change
> arch/mips/Makefile corresponding to the description?
> 

In general this seems correct.

Another point is that the kernel has this:

ifdef CONFIG_CROSSCOMPILE
CROSS_COMPILE           := $(tool-prefix)
endif

config CROSSCOMPILE
        bool "Are you using a crosscompiler"
        help
          Say Y here if you are compiling the kernel on a different
          architecture than the one it is intended to run on.


I think the Kconfig could be changed to say that CONFIG_CROSSCOMPILE
makes the build system use a built-in default tool prefix.

-Geoff


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