Re: [PATCH 14/14] klp-build: Support cross-compilation

[Josh Poimboeuf]

On Tue, Mar 17, 2026 at 11:21:43AM -0700, Song Liu wrote:
> On Tue, Mar 17, 2026 at 10:52 AM Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote:
> [...]
> > >
> > > Yeah, I think that would be a good idea.  Will do that for v2.
> >
> > So, in general ARCH is complicated.  For example:
> >
> >  - ARCH=arm64 would never match "uname -m" (aarch64)
> >  - ARCH=i386 would use the same gcc binary (no cross-compiler needed)
> >  - I'm sure there are many other edge cases...
> 
> Agreed. I haven't worked with i386 for a long time, but I did notice
> the arm64 vs. aarch64 difference.
> 
> > Instead of a manual error, it may be simpler to just let the build fail
> > naturally if the user doesn't set the right ARCH.
> >
> > Though, I think the check can be improved slightly, as ARCH is a
> > reasonably good indicator that cross-compiling is happening.  So I can
> > at least add an ARCH check at the beginning like so?
> >
> > cross_compile_init() {
> >         if [[ ! -v ARCH ]]; then
> >                 OBJCOPY=objcopy
> >                 return 0
> >         fi
> >
> >         if [[ -v LLVM ]]; then
> >                 OBJCOPY=llvm-objcopy
> >         else
> >                 OBJCOPY="${CROSS_COMPILE:-}objcopy"
> >         fi
> > }
> 
> Do we need ARCH when CROSS_COMPILE is set? I was
> under the impression that CROSS_COMPILE doesn't require
> ARCH.

If CROSS_COMPILE is used without ARCH, it will just try to use the host
arch.  I'm not sure if that's considered cross-compiling?   I suppose it
should use the CROSS_COMPILE version of objcopy in that case?  Though in
practice it probably doesn't matter.

I guess the original version of the function is probably fine and we
don't need to complicate matters.

-- 
Josh