Subject: Re: [PATCH] powerpc: remove meaningless KBUILD_ARFLAGS addition

From: Segher Boessenkool <[email-masked]>
Date: Wed, 17 Jul 2019 09:38:11 -0500

On Tue, Jul 16, 2019 at 10:15:47PM +1000, Michael Ellerman wrote:
> Segher Boessenkool <[email-masked]> writes:
> And it's definitely calling ar with no flags, eg:
> 
>   rm -f init/built-in.a; powerpc-linux-ar rcSTPD init/built-in.a init/main.o init/version.o init/do_mounts.o init/do_mounts_rd.o init/do_mounts_initrd.o init/do_mounts_md.o init/initramfs.o init/init_task.o

This uses thin archives.  Those will work fine.

The failing case was empty files IIRC, stuff created from no inputs.

> So presumably at some point ar learnt to cope with objects that don't
> match its default? (how do I ask it what its default is?)

The first supported target in the --help list is the default, I think?

$ powerpc-linux-ar --help
 [...]
powerpc-linux-ar: supported targets: elf32-powerpc aixcoff-rs6000 elf32-powerpcle ppcboot elf64-powerpc elf64-powerpcle elf64-little elf64-big elf32-little elf32-big plugin srec symbolsrec verilog tekhex binary ihex

$ powerpc64-linux-ar --help
 [...]
powerpc64-linux-ar: supported targets: elf64-powerpc elf64-powerpcle elf32-powerpc elf32-powerpcle aixcoff-rs6000 aixcoff64-rs6000 aix5coff64-rs6000 elf64-little elf64-big elf32-little elf32-big plugin srec symbolsrec verilog tekhex binary ihex

$ powerpc64le-linux-ar --help
 [...]
powerpc64le-linux-ar: supported targets: elf64-powerpcle elf64-powerpc elf32-powerpcle elf32-powerpc aixcoff-rs6000 aixcoff64-rs6000 aix5coff64-rs6000 elf64-little elf64-big elf32-little elf32-big plugin srec symbolsrec verilog tekhex binary ihex

$ powerpcle-linux-ar --help
 [...]
powerpcle-linux-ar: supported targets: elf32-powerpcle aixcoff-rs6000 elf32-powerpc ppcboot elf64-powerpc elf64-powerpcle elf64-little elf64-big elf32-little elf32-big plugin srec symbolsrec verilog tekhex binary ihex

> > Then again, does that work at *all* nowadays?  Do we even consider that
> > important, *should* it work?
> 
> Yes and yes. There were a lot of bugs in the kernel makefiles after we
> added LE support which prevented a biarch/biendian compiler from working.
> But now it does work and we want it to keep working because it means you
> can have a single compiler for building 32-bit, 64-bit BE & 64-bit LE.

Good to hear :-)

Segher