[PATCH] Make m68k cross compile like every other architecture.

[PATCH] Make m68k cross compile like every other architecture.

[Rob Landley]

From: Rob Landley <rob@landley.net>

Rip out hardwired cross compiler name assumption that only m68k makes.

Signed-off-by: Rob Landley <rob@landley.net>
---
When you cross compile, you have to set the prefix CROSS_COMPILE to your
cross compiler prefix.  You need to do this for all targets (arm, mips, ppc,
x86-64 on x86, etc).  This is not specific to m68k, and this value is
supplied _to_ the build, not supplied _by_ the build.

The build shouldn't unconditionally overwrite the existing value of this
variable with one it makes up.  It has no idea what I called my cross compiler.

 arch/m68k/Makefile |    7 -------
 1 file changed, 7 deletions(-)

diff -r 79f0ea1e0e70 arch/m68k/Makefile
--- a/arch/m68k/Makefile	Tue Oct 09 21:00:40 2007 +0000
+++ b/arch/m68k/Makefile	Wed Oct 10 17:02:17 2007 -0500
@@ -13,17 +13,10 @@
 # Copyright (C) 1994 by Hamish Macdonald
 #
 
-# test for cross compiling
-COMPILE_ARCH = $(shell uname -m)
-
 # override top level makefile
 AS += -m68020
 LDFLAGS := -m m68kelf
 LDFLAGS_MODULE += -T $(srctree)/arch/m68k/kernel/module.lds
-ifneq ($(COMPILE_ARCH),$(ARCH))
-	# prefix for cross-compiling binaries
-	CROSS_COMPILE = m68k-linux-gnu-
-endif
 
 ifdef CONFIG_SUN3
 LDFLAGS_vmlinux = -N

-- 
"One of my most productive days was throwing away 1000 lines of code."
  - Ken Thompson.

Re: [PATCH] Make m68k cross compile like every other architecture.

[Geert Uytterhoeven]

On Wed, 10 Oct 2007, Rob Landley wrote:
> From: Rob Landley <rob@landley.net>
> 
> Rip out hardwired cross compiler name assumption that only m68k makes.
> 
> Signed-off-by: Rob Landley <rob@landley.net>
> ---
> When you cross compile, you have to set the prefix CROSS_COMPILE to your
> cross compiler prefix.  You need to do this for all targets (arm, mips, ppc,
> x86-64 on x86, etc).  This is not specific to m68k, and this value is
> supplied _to_ the build, not supplied _by_ the build.
> 
> The build shouldn't unconditionally overwrite the existing value of this
> variable with one it makes up.  It has no idea what I called my cross compiler.

The build does not unconditionally overwrite the existing value of this
variable. You can specify the name of your cross compiler like this:

    make CROSS_COMPILE=m68k-linux-

BTW, m68k-linux-gnu- is the default name for a m68k cross compiler.

>  arch/m68k/Makefile |    7 -------
>  1 file changed, 7 deletions(-)
> 
> diff -r 79f0ea1e0e70 arch/m68k/Makefile
> --- a/arch/m68k/Makefile	Tue Oct 09 21:00:40 2007 +0000
> +++ b/arch/m68k/Makefile	Wed Oct 10 17:02:17 2007 -0500
> @@ -13,17 +13,10 @@
>  # Copyright (C) 1994 by Hamish Macdonald
>  #
>  
> -# test for cross compiling
> -COMPILE_ARCH = $(shell uname -m)
> -
>  # override top level makefile
>  AS += -m68020
>  LDFLAGS := -m m68kelf
>  LDFLAGS_MODULE += -T $(srctree)/arch/m68k/kernel/module.lds
> -ifneq ($(COMPILE_ARCH),$(ARCH))
> -	# prefix for cross-compiling binaries
> -	CROSS_COMPILE = m68k-linux-gnu-
> -endif
>  
>  ifdef CONFIG_SUN3
>  LDFLAGS_vmlinux = -N

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

Re: [PATCH] Make m68k cross compile like every other architecture.

[Rob Landley]

On Thursday 11 October 2007 2:25:19 am Geert Uytterhoeven wrote:
> On Wed, 10 Oct 2007, Rob Landley wrote:
> > From: Rob Landley <rob@landley.net>
> >
> > Rip out hardwired cross compiler name assumption that only m68k makes.
> >
> > Signed-off-by: Rob Landley <rob@landley.net>
> > ---
> > When you cross compile, you have to set the prefix CROSS_COMPILE to your
> > cross compiler prefix.  You need to do this for all targets (arm, mips,
> > ppc, x86-64 on x86, etc).  This is not specific to m68k, and this value
> > is supplied _to_ the build, not supplied _by_ the build.
> >
> > The build shouldn't unconditionally overwrite the existing value of this
> > variable with one it makes up.  It has no idea what I called my cross
> > compiler.
>
> The build does not unconditionally overwrite the existing value of this
> variable. You can specify the name of your cross compiler like this:
>
>     make CROSS_COMPILE=m68k-linux-

I noticed this because you have to specify ARCH for "make headers_install" but 
don't have to specify a CROSS_COMPILE prefix for that because it doesn't 
build anything.  Yet the first line it spits out is a complaint that it can't 
find m68k-linux-gnu-gcc.

I do note that the error message doesn't stop the build, and seems to be 
ignored...

> BTW, m68k-linux-gnu- is the default name for a m68k cross compiler.

*shrug*  This is the eleventh target I've tried to build, and the first one 
that has this behavior.  It seemed unnecessary at best.

Rob
-- 
"One of my most productive days was throwing away 1000 lines of code."
  - Ken Thompson.

Re: [PATCH] Make m68k cross compile like every other architecture.

[Sam Ravnborg]

On Thu, Oct 11, 2007 at 09:25:19AM +0200, Geert Uytterhoeven wrote:
> On Wed, 10 Oct 2007, Rob Landley wrote:
> > From: Rob Landley <rob@landley.net>
> > 
> > Rip out hardwired cross compiler name assumption that only m68k makes.
> > 
> > Signed-off-by: Rob Landley <rob@landley.net>
> > ---
> > When you cross compile, you have to set the prefix CROSS_COMPILE to your
> > cross compiler prefix.  You need to do this for all targets (arm, mips, ppc,
> > x86-64 on x86, etc).  This is not specific to m68k, and this value is
> > supplied _to_ the build, not supplied _by_ the build.
> > 
> > The build shouldn't unconditionally overwrite the existing value of this
> > variable with one it makes up.  It has no idea what I called my cross compiler.
> 
> The build does not unconditionally overwrite the existing value of this
> variable. You can specify the name of your cross compiler like this:
> 
>     make CROSS_COMPILE=m68k-linux-
> 
> BTW, m68k-linux-gnu- is the default name for a m68k cross compiler.

For "make headers_install" this is not good.
But I see there is confliting usages here.
1) current functionality makes it easy to build a cross compiled m68k
2) suggested functionality makes it easy to do make headers_install

Btw. if you did:
CROSS_COMPILE ?= m68k-linux-

then I could do:
export CROSS_COMPILE=my-m68k-linux-
make

and still get the expected result.

	Sam


> 
> >  arch/m68k/Makefile |    7 -------
> >  1 file changed, 7 deletions(-)
> > 
> > diff -r 79f0ea1e0e70 arch/m68k/Makefile
> > --- a/arch/m68k/Makefile	Tue Oct 09 21:00:40 2007 +0000
> > +++ b/arch/m68k/Makefile	Wed Oct 10 17:02:17 2007 -0500
> > @@ -13,17 +13,10 @@
> >  # Copyright (C) 1994 by Hamish Macdonald
> >  #
> >  
> > -# test for cross compiling
> > -COMPILE_ARCH = $(shell uname -m)
> > -
> >  # override top level makefile
> >  AS += -m68020
> >  LDFLAGS := -m m68kelf
> >  LDFLAGS_MODULE += -T $(srctree)/arch/m68k/kernel/module.lds
> > -ifneq ($(COMPILE_ARCH),$(ARCH))
> > -	# prefix for cross-compiling binaries
> > -	CROSS_COMPILE = m68k-linux-gnu-
> > -endif
> >  
> >  ifdef CONFIG_SUN3
> >  LDFLAGS_vmlinux = -N
> 
> Gr{oetje,eeting}s,
> 
> 						Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> 							    -- Linus Torvalds
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH] Make m68k cross compile like every other architecture.

[Geert Uytterhoeven]

On Thu, 11 Oct 2007, Sam Ravnborg wrote:
> On Thu, Oct 11, 2007 at 09:25:19AM +0200, Geert Uytterhoeven wrote:
> > On Wed, 10 Oct 2007, Rob Landley wrote:
> > > From: Rob Landley <rob@landley.net>
> > > 
> > > Rip out hardwired cross compiler name assumption that only m68k makes.
> > > 
> > > Signed-off-by: Rob Landley <rob@landley.net>
> > > ---
> > > When you cross compile, you have to set the prefix CROSS_COMPILE to your
> > > cross compiler prefix.  You need to do this for all targets (arm, mips, ppc,
> > > x86-64 on x86, etc).  This is not specific to m68k, and this value is
> > > supplied _to_ the build, not supplied _by_ the build.
> > > 
> > > The build shouldn't unconditionally overwrite the existing value of this
> > > variable with one it makes up.  It has no idea what I called my cross compiler.
> > 
> > The build does not unconditionally overwrite the existing value of this
> > variable. You can specify the name of your cross compiler like this:
> > 
> >     make CROSS_COMPILE=m68k-linux-
> > 
> > BTW, m68k-linux-gnu- is the default name for a m68k cross compiler.
> 
> For "make headers_install" this is not good.
> But I see there is confliting usages here.
> 1) current functionality makes it easy to build a cross compiled m68k
> 
> Btw. if you did:
> CROSS_COMPILE ?= m68k-linux-
> 
> then I could do:
> export CROSS_COMPILE=my-m68k-linux-
> make
> 
> and still get the expected result.

That won't work, cfr. http://lkml.org/lkml/2007/5/6/58.

> 2) suggested functionality makes it easy to do make headers_install

This is something completely different (cfr. the other thread handling
it). If `make headers_install' doesn't need the cross compiler, it
should not try to execute it.

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

Re: [PATCH] Make m68k cross compile like every other architecture.

[Rob Landley]

On Thursday 11 October 2007 7:46:47 am Geert Uytterhoeven wrote:
> On Thu, 11 Oct 2007, Sam Ravnborg wrote:
> > On Thu, Oct 11, 2007 at 09:25:19AM +0200, Geert Uytterhoeven wrote:
> > > On Wed, 10 Oct 2007, Rob Landley wrote:
> > > > From: Rob Landley <rob@landley.net>
> > > >
> > > > Rip out hardwired cross compiler name assumption that only m68k
> > > > makes.
> > > >
> > > > Signed-off-by: Rob Landley <rob@landley.net>
> > > > ---
> > > > When you cross compile, you have to set the prefix CROSS_COMPILE to
> > > > your cross compiler prefix.  You need to do this for all targets
> > > > (arm, mips, ppc, x86-64 on x86, etc).  This is not specific to m68k,
> > > > and this value is supplied _to_ the build, not supplied _by_ the
> > > > build.
> > > >
> > > > The build shouldn't unconditionally overwrite the existing value of
> > > > this variable with one it makes up.  It has no idea what I called my
> > > > cross compiler.
> > >
> > > The build does not unconditionally overwrite the existing value of this
> > > variable. You can specify the name of your cross compiler like this:
> > >
> > >     make CROSS_COMPILE=m68k-linux-
> > >
> > > BTW, m68k-linux-gnu- is the default name for a m68k cross compiler.
> >
> > For "make headers_install" this is not good.
> > But I see there is confliting usages here.
> > 1) current functionality makes it easy to build a cross compiled m68k
> >
> > Btw. if you did:
> > CROSS_COMPILE ?= m68k-linux-
> >
> > then I could do:
> > export CROSS_COMPILE=my-m68k-linux-
> > make
> >
> > and still get the expected result.
>
> That won't work, cfr. http://lkml.org/lkml/2007/5/6/58.

Reading the patch in that link, recent cross compilers from _where_?  
Buildroot?  Cross-tools?  Gentoo embedded?  Cross Linux From Scratch?  My 
Firmware Linux project?

You assume they all use the same name, yet your patch changes them from one 
default name to another default name, presumably due to a gcc version change 
becoming increasingly political about the GNU/Linux/Dammit thing...

None of the other targets I've tried attempt to _supply_ a default.  Just like 
the Linux kernel errors out early in the build if you distclean and then try 
to run "make" without having run config first.  It doesn't run "defconfig" 
for you and continue on in that case.  But m68k, uniquely, assumes it knows 
what you want to do when you didn't tell it.  Other targets do not do this.

Rob
-- 
"One of my most productive days was throwing away 1000 lines of code."
  - Ken Thompson.

Re: [PATCH] Make m68k cross compile like every other architecture.

[Paul Mundt]

On Thu, Oct 11, 2007 at 08:27:12AM -0500, Rob Landley wrote:
> On Thursday 11 October 2007 7:46:47 am Geert Uytterhoeven wrote:
> > On Thu, 11 Oct 2007, Sam Ravnborg wrote:
> > > On Thu, Oct 11, 2007 at 09:25:19AM +0200, Geert Uytterhoeven wrote:
> > > > BTW, m68k-linux-gnu- is the default name for a m68k cross compiler.
> > >
> > > For "make headers_install" this is not good.
> > > But I see there is confliting usages here.
> > > 1) current functionality makes it easy to build a cross compiled m68k
> > >
> > > Btw. if you did:
> > > CROSS_COMPILE ?= m68k-linux-
> > >
> > > then I could do:
> > > export CROSS_COMPILE=my-m68k-linux-
> > > make
> > >
> > > and still get the expected result.
> >
> > That won't work, cfr. http://lkml.org/lkml/2007/5/6/58.
> 
> Reading the patch in that link, recent cross compilers from _where_?  
> Buildroot?  Cross-tools?  Gentoo embedded?  Cross Linux From Scratch?  My 
> Firmware Linux project?
> 
> You assume they all use the same name, yet your patch changes them from one 
> default name to another default name, presumably due to a gcc version change 
> becoming increasingly political about the GNU/Linux/Dammit thing...
> 
> None of the other targets I've tried attempt to _supply_ a default.  Just like 
> the Linux kernel errors out early in the build if you distclean and then try 
> to run "make" without having run config first.  It doesn't run "defconfig" 
> for you and continue on in that case.  But m68k, uniquely, assumes it knows 
> what you want to do when you didn't tell it.  Other targets do not do this.
> 
Many platforms used to do this. For most of them it didn't end up being
useful given all of the target variant, so they just got removed. If
that's not the case for m68k and it's still useful for people there, then
there's no reason to remove it. If you want to overload it you are free
to, but Geert is right that headers_install shouldn't be calling the
cross compiler if it has no dependency on it. Fixing bugs is preferable
to fixing symptoms.

Re: [PATCH] Make m68k cross compile like every other architecture.

[Geert Uytterhoeven]

On Thu, 11 Oct 2007, Rob Landley wrote:
> On Thursday 11 October 2007 7:46:47 am Geert Uytterhoeven wrote:
> > On Thu, 11 Oct 2007, Sam Ravnborg wrote:
> > > On Thu, Oct 11, 2007 at 09:25:19AM +0200, Geert Uytterhoeven wrote:
> > > > On Wed, 10 Oct 2007, Rob Landley wrote:
> > > > > Rip out hardwired cross compiler name assumption that only m68k
> > > > > makes.
> > > > >
> > > > > Signed-off-by: Rob Landley <rob@landley.net>
> > > > > ---
> > > > > When you cross compile, you have to set the prefix CROSS_COMPILE to
> > > > > your cross compiler prefix.  You need to do this for all targets
> > > > > (arm, mips, ppc, x86-64 on x86, etc).  This is not specific to m68k,
> > > > > and this value is supplied _to_ the build, not supplied _by_ the
> > > > > build.
> > > > >
> > > > > The build shouldn't unconditionally overwrite the existing value of
> > > > > this variable with one it makes up.  It has no idea what I called my
> > > > > cross compiler.
> > > >
> > > > The build does not unconditionally overwrite the existing value of this
> > > > variable. You can specify the name of your cross compiler like this:
> > > >
> > > >     make CROSS_COMPILE=m68k-linux-
> > > >
> > > > BTW, m68k-linux-gnu- is the default name for a m68k cross compiler.
> > >
> > > For "make headers_install" this is not good.
> > > But I see there is confliting usages here.
> > > 1) current functionality makes it easy to build a cross compiled m68k
> > >
> > > Btw. if you did:
> > > CROSS_COMPILE ?= m68k-linux-
> > >
> > > then I could do:
> > > export CROSS_COMPILE=my-m68k-linux-
> > > make
> > >
> > > and still get the expected result.
> >
> > That won't work, cfr. http://lkml.org/lkml/2007/5/6/58.
> 
> Reading the patch in that link, recent cross compilers from _where_?  
> Buildroot?  Cross-tools?  Gentoo embedded?  Cross Linux From Scratch?  My 
> Firmware Linux project?
>
> You assume they all use the same name, yet your patch changes them from one 
> default name to another default name, presumably due to a gcc version change 
> becoming increasingly political about the GNU/Linux/Dammit thing...

Compilers build from the only remaining distribution that supports (sort
of) m68k: Debian.

> None of the other targets I've tried attempt to _supply_ a default.  Just like 
Obviously you haven't tried them all...

> the Linux kernel errors out early in the build if you distclean and then try 
> to run "make" without having run config first.  It doesn't run "defconfig" 
> for you and continue on in that case.  But m68k, uniquely, assumes it knows 
> what you want to do when you didn't tell it.  Other targets do not do this.

If you cross compile for m68k and don't specify a toolchain, you get a
default one: the one the m68k developers use.

On some other architectures, you always have to specify the toolchain.
What's wrong with providing a default?

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

Re: [PATCH] Make m68k cross compile like every other architecture.

[Sam Ravnborg]

> 
> > 2) suggested functionality makes it easy to do make headers_install
> 
> This is something completely different (cfr. the other thread handling
> it). If `make headers_install' doesn't need the cross compiler, it
> should not try to execute it.

This is obviously correct.
It happens that we execute gcc several times for just about any target
due to the:
CFLAGS += $(call cc-option, xxx)

And refactoring the top-level Makefile to avoid this is on my TODO list.
But it is a major crunch to do correct...

The primary objective to do so is btw not to solve this issue but
more to get the top-level Makefile off the top-10 list of the most
ureadable unmaitaninable unhackable code in the kernel.

	Sam

Re: [PATCH] Make m68k cross compile like every other architecture.

[Finn Thain]

On Thu, 11 Oct 2007, Geert Uytterhoeven wrote:

> > Reading the patch in that link, recent cross compilers from _where_?  
> > Buildroot?  Cross-tools?  Gentoo embedded?  Cross Linux From Scratch?  
> > My Firmware Linux project?
> >
> > You assume they all use the same name, yet your patch changes them 
> > from one default name to another default name, presumably due to a gcc 
> > version change becoming increasingly political about the 
> > GNU/Linux/Dammit thing...
> 
> Compilers build from the only remaining distribution that supports (sort 
> of) m68k: Debian.

Maybe. I use an old Cross LFS build, as well as Debian (does Debian 
officially support m68k?), and there also exists an unofficial Gentoo 
port.

> If you cross compile for m68k and don't specify a toolchain, you get a 
> default one: the one the m68k developers use.
> 
> On some other architectures, you always have to specify the toolchain. 
> What's wrong with providing a default?

Nothing, except that uniformity across platforms follows the principal of 
least suprise. That generally makes life easier downstream.

I personally have created and used m68k cross toolchains as "m68k-linux", 
"m68k-linux-gnu" and "m68k-unknown-linux-gnu". AFAIK it's quite arbitrary.

This wasn't an issue before we came to depend on cross compilers. Since we 
tend to need them more as compilation becomes more expensive, IMHO we 
should follow the practice of the embedded architectures.

-f

> 
> Gr{oetje,eeting}s,
> 
> 						Geert

Re: [PATCH] Make m68k cross compile like every other architecture.

[Rob Landley]

On Thursday 11 October 2007 11:26:07 am Finn Thain wrote:
> On Thu, 11 Oct 2007, Geert Uytterhoeven wrote:
> > > Reading the patch in that link, recent cross compilers from _where_?
> > > Buildroot?  Cross-tools?  Gentoo embedded?  Cross Linux From Scratch?
> > > My Firmware Linux project?
> > >
> > > You assume they all use the same name, yet your patch changes them
> > > from one default name to another default name, presumably due to a gcc
> > > version change becoming increasingly political about the
> > > GNU/Linux/Dammit thing...
> >
> > Compilers build from the only remaining distribution that supports (sort
> > of) m68k: Debian.
>
> Maybe. I use an old Cross LFS build, as well as Debian (does Debian
> officially support m68k?), and there also exists an unofficial Gentoo
> port.

I noticed the cruft in this target because I'm attempting to support it in 
Firmware Linux (http://landley.net/code/firmware), on the theory that a patch 
was posted to the qemu mailing list to add m68k support to qemu, so it's 
probably only a matter of time until it gets merged and an m68k system board 
added to the emulator: 
http://lists.gnu.org/archive/html/qemu-devel/2007-07/msg00015.html

If the _goal_ is that Debian be the only distribution to support m68k, then 
obviously the name it uses can be hardwired into the code because that's all 
that can ever matter, by definition.

> > If you cross compile for m68k and don't specify a toolchain, you get a
> > default one: the one the m68k developers use.
> >
> > On some other architectures, you always have to specify the toolchain.
> > What's wrong with providing a default?
>
> Nothing, except that uniformity across platforms follows the principal of
> least suprise. That generally makes life easier downstream.
>
> I personally have created and used m68k cross toolchains as "m68k-linux",
> "m68k-linux-gnu" and "m68k-unknown-linux-gnu". AFAIK it's quite arbitrary.

My toolchains override the default prefix to just the target, resulting 
in "m68k-gcc".  (It's shorter, and when you're creating a dozen toolchains 
having them all say -linux- in the middle of every command name gets a bit 
silly...)

When it started complaining about "m68k-linux-gnu-gcc" (which is _not_ what my 
cross compiler is called) I spent half an hour tracking down where it was 
getting that name from and what exactly was going on.  (Was my build script 
supplying the wrong name?  Did something set an environment variable it 
shouldn't have?  Did the gcc build suddenly reveal another strange buried 
corner case that made it revert to a default against explicit instructions 
_again_?)

When I found the surprising behavior that cost me time and effort to diagnose, 
I submitted a patch so it wouldn't confuse future developers the first time 
_they_ try to build m68k.  (Yes, I think there might be such.  Call me 
crazy.)  I've seen "didn't specify any cross compiler" failures before, on 
arm and x86-64 and mips and sparc and so on.  I've seen it in the linux 
kernel, in busybox, in uClibc, and in various gnu packages 
with ./configureitis.  This is the first time I've seen a package confidently 
decide for itself to use a compiler name that isn't in the $PATH, and 
especially the first time I've seen Linux do it.  It cost me time to 
disagnose because it looks like it's getting a CROSS_COMPILE setting from its 
environment somehow, and the logical thing to do is look at that environment 
(and the build scripts driving it, and the temp files) to see where such a 
thing might be leaking in from.  The fact it might be hallucinating its own 
value was not my first guess, because nothing else I've encountered does that 
in this context.

> This wasn't an issue before we came to depend on cross compilers. Since we
> tend to need them more as compilation becomes more expensive, IMHO we
> should follow the practice of the embedded architectures.

That topic's a can of worms, but I point out that you always needed a cross 
compiler to bootstrap a new platform. :)

If you're going to support cross compiling at all, you might as well do it 
more or less consistently for all targets.

Rob
-- 
"One of my most productive days was throwing away 1000 lines of code."
  - Ken Thompson.

Re: [PATCH] Make m68k cross compile like every other architecture.

[Geert Uytterhoeven]

On Thu, 11 Oct 2007, Rob Landley wrote:
> On Thursday 11 October 2007 11:26:07 am Finn Thain wrote:
> My toolchains override the default prefix to just the target, resulting 
> in "m68k-gcc".  (It's shorter, and when you're creating a dozen toolchains 
> having them all say -linux- in the middle of every command name gets a bit 
> silly...)
> 
> When it started complaining about "m68k-linux-gnu-gcc" (which is _not_ what my 
> cross compiler is called) I spent half an hour tracking down where it was 
> getting that name from and what exactly was going on.  (Was my build script 
> supplying the wrong name?  Did something set an environment variable it 
> shouldn't have?  Did the gcc build suddenly reveal another strange buried 
> corner case that made it revert to a default against explicit instructions 
> _again_?)
> 
> When I found the surprising behavior that cost me time and effort to diagnose, 
> I submitted a patch so it wouldn't confuse future developers the first time 
> _they_ try to build m68k.  (Yes, I think there might be such.  Call me 
> crazy.)  I've seen "didn't specify any cross compiler" failures before, on 
> arm and x86-64 and mips and sparc and so on.  I've seen it in the linux 
> kernel, in busybox, in uClibc, and in various gnu packages 
> with ./configureitis.  This is the first time I've seen a package confidently 
> decide for itself to use a compiler name that isn't in the $PATH, and 
> especially the first time I've seen Linux do it.  It cost me time to 
> disagnose because it looks like it's getting a CROSS_COMPILE setting from its 
> environment somehow, and the logical thing to do is look at that environment 
> (and the build scripts driving it, and the temp files) to see where such a 
> thing might be leaking in from.  The fact it might be hallucinating its own 
> value was not my first guess, because nothing else I've encountered does that 
> in this context.
> 
> > This wasn't an issue before we came to depend on cross compilers. Since we
> > tend to need them more as compilation becomes more expensive, IMHO we
> > should follow the practice of the embedded architectures.
> 
> That topic's a can of worms, but I point out that you always needed a cross 
> compiler to bootstrap a new platform. :)
> 
> If you're going to support cross compiling at all, you might as well do it 
> more or less consistently for all targets.

If your cross-compiler is called differently than the default on in
arch/*/Makefile, what's the problem with calling?

    make ARCH=myarch CROSS_COMPILE=my-cross-compile-prefx-

This has been working for +10 years on all non-ia32 platforms I ever worked on.

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

Re: [PATCH] Make m68k cross compile like every other architecture.

[Finn Thain]

> 
> If your cross-compiler is called differently than the default on in 
> arch/*/Makefile,

Part of the problem is that there is no compelling default. The name of 
the cross-compiler can vary depending on the chosen executable prefix or 
the chosen target tuple.

Let's say I create new cross toolchains for both m68k and powerpc. I use 
the "m68k-linux-gnu" to follow the m68k default, but let's assume powerpc 
users prefer their default "powerpc-linux" so I follow that too. The 
result is that I now have gcc's -B option working (or not working) in 
suprising ways too.

Uniformity is more helpful downstream than a different arbitrary default 
for each architecture. Debian should patch their default into their kernel 
source packages if they've standardised on cross compiler prefixes.

> what's the problem with calling?
> 
>     make ARCH=myarch CROSS_COMPILE=my-cross-compile-prefx-
> 
> This has been working for +10 years on all non-ia32 platforms I ever worked on.

But there is no problem with calling that (?). Rob's patch doesn't change 
this.

-f

> 
> Gr{oetje,eeting}s,
> 
> 						Geert
> 

Re: [PATCH] Make m68k cross compile like every other architecture.

[Geert Uytterhoeven]

On Fri, 12 Oct 2007, Finn Thain wrote:
> > If your cross-compiler is called differently than the default on in 
> > arch/*/Makefile,
> 
> Part of the problem is that there is no compelling default. The name of 
> the cross-compiler can vary depending on the chosen executable prefix or 
> the chosen target tuple.
> 
> Let's say I create new cross toolchains for both m68k and powerpc. I use 
> the "m68k-linux-gnu" to follow the m68k default, but let's assume powerpc 
> users prefer their default "powerpc-linux" so I follow that too. The 
> result is that I now have gcc's -B option working (or not working) in 
> suprising ways too.
> 
> Uniformity is more helpful downstream than a different arbitrary default 
> for each architecture. Debian should patch their default into their kernel 
> source packages if they've standardised on cross compiler prefixes.
> 
> > what's the problem with calling?
> > 
> >     make ARCH=myarch CROSS_COMPILE=my-cross-compile-prefx-
> > 
> > This has been working for +10 years on all non-ia32 platforms I ever worked on.
> 
> But there is no problem with calling that (?). Rob's patch doesn't change 
> this.

But it makes life harder for the people who use it daily.

If the consensus is to not provide default cross compiler prefixes in
arch/*/Makefile, fine for me, but IFF it's done for all architectures
(i.e. check with the blackfin, h8300, mips, parisc, and xtensa people
first).

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

Re: [PATCH] Make m68k cross compile like every other architecture.

[Sam Ravnborg]

On Fri, Oct 12, 2007 at 10:51:00AM +0200, Geert Uytterhoeven wrote:
> On Fri, 12 Oct 2007, Finn Thain wrote:
> > > If your cross-compiler is called differently than the default on in 
> > > arch/*/Makefile,
> > 
> > Part of the problem is that there is no compelling default. The name of 
> > the cross-compiler can vary depending on the chosen executable prefix or 
> > the chosen target tuple.
> > 
> > Let's say I create new cross toolchains for both m68k and powerpc. I use 
> > the "m68k-linux-gnu" to follow the m68k default, but let's assume powerpc 
> > users prefer their default "powerpc-linux" so I follow that too. The 
> > result is that I now have gcc's -B option working (or not working) in 
> > suprising ways too.
> > 
> > Uniformity is more helpful downstream than a different arbitrary default 
> > for each architecture. Debian should patch their default into their kernel 
> > source packages if they've standardised on cross compiler prefixes.
> > 
> > > what's the problem with calling?
> > > 
> > >     make ARCH=myarch CROSS_COMPILE=my-cross-compile-prefx-
> > > 
> > > This has been working for +10 years on all non-ia32 platforms I ever worked on.
> > 
> > But there is no problem with calling that (?). Rob's patch doesn't change 
> > this.
> 
> But it makes life harder for the people who use it daily.
> 
> If the consensus is to not provide default cross compiler prefixes in
> arch/*/Makefile, fine for me, but IFF it's done for all architectures
> (i.e. check with the blackfin, h8300, mips, parisc, and xtensa people
> first).

Test if the expected gcc is available and set CROSS_COMPILE
if it is present. Otherwise do not touch CROSS_COMPILE.

m68kgcc := $(shell "test if m68k-gcc is present and echo 'y' if so")
ifeq ($(m68kgcc,y)
        CROSS_COMPILE := m68k-foo
endif

Then everyone is happy.
parisc does something similar.

	Sam

Re: [PATCH] Make m68k cross compile like every other architecture.

[Geert Uytterhoeven]

On Fri, 12 Oct 2007, Sam Ravnborg wrote:
> On Fri, Oct 12, 2007 at 10:51:00AM +0200, Geert Uytterhoeven wrote:
> > On Fri, 12 Oct 2007, Finn Thain wrote:
> > > > If your cross-compiler is called differently than the default on in 
> > > > arch/*/Makefile,
> > > 
> > > Part of the problem is that there is no compelling default. The name of 
> > > the cross-compiler can vary depending on the chosen executable prefix or 
> > > the chosen target tuple.
> > > 
> > > Let's say I create new cross toolchains for both m68k and powerpc. I use 
> > > the "m68k-linux-gnu" to follow the m68k default, but let's assume powerpc 
> > > users prefer their default "powerpc-linux" so I follow that too. The 
> > > result is that I now have gcc's -B option working (or not working) in 
> > > suprising ways too.
> > > 
> > > Uniformity is more helpful downstream than a different arbitrary default 
> > > for each architecture. Debian should patch their default into their kernel 
> > > source packages if they've standardised on cross compiler prefixes.
> > > 
> > > > what's the problem with calling?
> > > > 
> > > >     make ARCH=myarch CROSS_COMPILE=my-cross-compile-prefx-
> > > > 
> > > > This has been working for +10 years on all non-ia32 platforms I ever worked on.
> > > 
> > > But there is no problem with calling that (?). Rob's patch doesn't change 
> > > this.
> > 
> > But it makes life harder for the people who use it daily.
> > 
> > If the consensus is to not provide default cross compiler prefixes in
> > arch/*/Makefile, fine for me, but IFF it's done for all architectures
> > (i.e. check with the blackfin, h8300, mips, parisc, and xtensa people
> > first).
> 
> Test if the expected gcc is available and set CROSS_COMPILE
> if it is present. Otherwise do not touch CROSS_COMPILE.
> 
> m68kgcc := $(shell "test if m68k-gcc is present and echo 'y' if so")
> ifeq ($(m68kgcc,y)
>         CROSS_COMPILE := m68k-foo
> endif
> 
> Then everyone is happy.
> parisc does something similar.

64-bit parisc tests if /usr/bin/hppa64-linux-gnu- exists.
If yes, it sets CROSS_COMPILE to hppa64-linux-gnu-.
If no, it sets CROSS_COMPILE to hppa64-linux-

32-bit parisc unconditionally sets CROSS_COMPILE to hppa-linux-.

This still breaks Rob's setup if his compiler is called differently.

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?

Subject: m68k: Improve cross-compiler autodetection

m68k: Improve cross-compiler autodetection

Set CROSS_COMPILE to m68k-linux-gnu- resp. m68k-linux-, but only if such a
cross compiler is found in your $PATH

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
 arch/m68k/Makefile |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

--- a/arch/m68k/Makefile
+++ b/arch/m68k/Makefile
@@ -22,7 +22,17 @@ LDFLAGS := -m m68kelf
 LDFLAGS_MODULE += -T $(srctree)/arch/m68k/kernel/module.lds
 ifneq ($(COMPILE_ARCH),$(ARCH))
 	# prefix for cross-compiling binaries
-	CROSS_COMPILE = m68k-linux-gnu-
+	m68k-linux-gnu-gcc := $(shell if [ `which m68k-linux-gnu-gcc` ]; then \
+		echo y; fi)
+	ifeq ($(m68k-linux-gnu-gcc),y)
+		CROSS_COMPILE := m68k-linux-gnu-
+	else
+		m68k-linux-gcc := $(shell if [ `which m68k-linux-gcc` ]; then \
+			echo y; fi)
+		ifeq ($(m68k-linux-gcc),y)
+			CROSS_COMPILE := m68k-linux-
+		endif
+	endif
 endif
 
 ifdef CONFIG_SUN3

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

Re: [PATCH] Make m68k cross compile like every other architecture.

[Rob Landley]

On Monday 15 October 2007 3:25:35 pm Geert Uytterhoeven wrote:
> 64-bit parisc tests if /usr/bin/hppa64-linux-gnu- exists.
> If yes, it sets CROSS_COMPILE to hppa64-linux-gnu-.
> If no, it sets CROSS_COMPILE to hppa64-linux-
>
> 32-bit parisc unconditionally sets CROSS_COMPILE to hppa-linux-.
>
> This still breaks Rob's setup if his compiler is called differently.

Another thing to take into account is that kconfig was recently changed to 
save ARCH and CROSS_COMPILE in the .config file:

http://lwn.net/Articles/253889/

Presumably that means you'd only have to specify your arch and cross compiler 
during config, and then if you re-used that config it would re-use those 
settings.  But the existing makefile discards anything that isn't explicitly 
overridden on the make command line at each stage of the build.

It seems to me any fix should only reset CROSS_COMPILE if there isn't already 
a value for it.  (Otherwise there's a potentially subtle bug where a year 
from now you might have "m68k-linux-gnu-gcc" and "m68k-linux-gnu-pcc" and 
want to compare the results of building with the different compilers.)

I still lean towards considering any attempt to cross compile without setting 
CROSS_COMPILE an error, and not guessing at what the user meant.  But perhaps 
that's just personal preference...

Rob
-- 
"One of my most productive days was throwing away 1000 lines of code."
  - Ken Thompson.

Re: [PATCH] Make m68k cross compile like every other architecture.

[Sam Ravnborg]

On Mon, Oct 15, 2007 at 07:31:54PM -0500, Rob Landley wrote:
> On Monday 15 October 2007 3:25:35 pm Geert Uytterhoeven wrote:
> > 64-bit parisc tests if /usr/bin/hppa64-linux-gnu- exists.
> > If yes, it sets CROSS_COMPILE to hppa64-linux-gnu-.
> > If no, it sets CROSS_COMPILE to hppa64-linux-
> >
> > 32-bit parisc unconditionally sets CROSS_COMPILE to hppa-linux-.
> >
> > This still breaks Rob's setup if his compiler is called differently.
> 
> Another thing to take into account is that kconfig was recently changed to 
> save ARCH and CROSS_COMPILE in the .config file:
> 
> http://lwn.net/Articles/253889/
The patch is postponed one merge window.
It caused troubles I had not foreseen which needs some attention first.
I plan to have it ready for next merge window.

	Sam

Re: [PATCH] Make m68k cross compile like every other architecture.

[Sam Ravnborg]

> 
> 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?

	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 $(c);                                    \
+		fi)))
+
+ifneq ($(SUBARCH),$(ARCH))
+        ifeq ($(CROSS_COMPILE),)
+                CROSS_COMPILE := $(call crossgcc, m68k-linux-gnu-)
+        endif
+endif
 
 # override top level makefile
 AS += -m68020
 LDFLAGS := -m m68kelf
 LDFLAGS_MODULE += -T $(srctree)/arch/m68k/kernel/module.lds
-ifneq ($(COMPILE_ARCH),$(ARCH))
-	# prefix for cross-compiling binaries
-	CROSS_COMPILE = m68k-linux-gnu-
-endif
 
 ifdef CONFIG_SUN3
 LDFLAGS_vmlinux = -N

Re: [PATCH] Make m68k cross compile like every other architecture.

[Rob Landley]

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?
>
> 	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...

> +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".

I suppose there's the weird corner case where your hostcc is tcc and your 
targetcc is gcc...

Rob
-- 
"One of my most productive days was throwing away 1000 lines of code."
  - Ken Thompson.

Re: [PATCH] Make m68k cross compile like every other architecture.

[Sam Ravnborg]

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