CROSS_COMPILE in environment variable

CROSS_COMPILE in environment variable

[Atsushi Nemoto]

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?

---
Atsushi Nemoto

Re: CROSS_COMPILE in environment variable

[Geoff Levand]

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

Re: CROSS_COMPILE in environment variable

[Atsushi Nemoto]

On Tue, 25 Apr 2006 11:32:46 -0700, Geoff Levand <geoffrey.levand@am.sony.com> wrote:
> I think the Kconfig could be changed to say that CONFIG_CROSSCOMPILE
> makes the build system use a built-in default tool prefix.

Already done by Ralf a few days ago :-)

---
Atsushi Nemoto