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SubjectRe: [PATCH] Make m68k cross compile like every other architecture.
On Fri, Oct 19, 2007 at 01:38:38AM -0500, Rob Landley wrote:
> On Thursday 18 October 2007 4:14:20 pm Sam Ravnborg wrote:
> > > Anyway, here's a try to make it autodetect m68k-linux-gnu-gcc and
> > > m68k-linux-gcc. Perhaps it can be generalized in kbuild, to allow
> > > arch/*/Makefile to set a list of possible cross-compiler prefixes?
> >
> > Here is my first try.
> > We only touch CROSS_COMPILE is empty and building for another arch.
> >
> > I can obviously move crossgcc part of this to core kbuild.
> > Any better name?
find-crossgcc

> >
> > Sam
> >
> >
> > diff --git a/arch/m68k/Makefile b/arch/m68k/Makefile
> > index 4a1bd44..6465bbe 100644
> > --- a/arch/m68k/Makefile
> > +++ b/arch/m68k/Makefile
> > @@ -13,17 +13,26 @@
> > # Copyright (C) 1994 by Hamish Macdonald
> > #
> >
> > -# test for cross compiling
> > -COMPILE_ARCH = $(shell uname -m)
> > +# usage:
> > +# CROSS_COMPILE := $(call crossgcc, foo bar /usr/bin/)
> > +# CROSS_COMPILE will be assinged the first prefix that point
> > +# to a gcc in the path
> > +crossgcc = $(word 1, $(foreach c,$(1), \
> > + $(shell set -e; \
> > + if (which $(strip $(c))$(CC)) > /dev/null 2>&1 ; then \
> > + echo $(c); \
> > + fi)))
>
> Searching for common cross compiler prefixes. Cool.
>
> What do you do if you want to use gcc as your host compiler, but m68k-pcc or
> arm-tcc as your target compiler? (I have no idea, CROSS_COMPILE=m68k- CC=pcc
> HOSTCC=gcc perhaps? Where does CC get set right now, anyway... Ah, top
> level Makefile:
> CC = $(CROSS_COMPILE)gcc
>
> That... should work. Odd and roundabout, but ok...
I see no other way to do it - and it seems obvious since you guessed right.

>
> > +ifneq ($(SUBARCH),$(ARCH))
> > + ifeq ($(CROSS_COMPILE),)
> > + CROSS_COMPILE := $(call crossgcc, m68k-linux-gnu-)
> > + endif
> > +endif
>
> Other query:
>
> If CROSS_COMPILE isn't set, and we iterate through all the standard prefixes
> but don't find a compiler, what's the right "fall off the end" behavior? If
> it falls back to using the host gcc, presumably the build will break if you
> feed your host gcc target flags it doesn't understand, but there are
> platforms where that sometimes doesn't seem to happen until the very end
> (building x86_64 on x86 for example)... Should the build just die with
> a "You are cross compiling, set CROSS_COMPILE".
No - that would be a bug. One may set up PATH sp gcc point to the
cross-compile gcc. fallback to native (host) gcc is expected and fine.

>
> I suppose there's the weird corner case where your hostcc is tcc and your
> targetcc is gcc...
I do not see why thats a problem - you just need to set both CC and HOSTCC.

Sam
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