Re: [PATCH, v2] Fix 32-bit build for --enable-targets=all

[Alan Modra <amodra@gmail.com>]

On Tue, Apr 26, 2022 at 10:07:53AM +0200, Jose E. Marchesi wrote:
> 
> Hi Alan.
> 
> > On Mon, Apr 25, 2022 at 08:40:54AM +0100, Luis Machado wrote:
> >> On 4/24/22 15:58, Joel Brobecker wrote:
> >> > Looking at this patch, I think you you may not have seen Alan's
> >> > comment, which je sent on Apr 18, saying:
> >> > 
> >> >      https://sourceware.org/pipermail/gdb-patches/2022-April/187960.html
> >> >      | Anything that requires 64-bit BFD support does not belong in
> >> >      | TARGET32_LIBOPCODES_CFILES.  In fact, the whole point of
> >> >      | TARGET32_LIBOPCODES_CFILES was to fix --enable-targets=all breakage on
> >> >      | 32-bit hosts without --enable-64-bit-bfd.  Why would you want to put
> >> >      | bpf here?  It's a 64-bit target!
> >> > 
> >> > (I see that you weren't in the list of direct recipients for that email)
> >> > 
> >> 
> >> Yes, it looks that way.
> >> 
> >> Unfortunately --enable-targets=all never really worked OK for 32-bit builds
> >> after splitting 64/32 targets. It is not clear to me if there are bugs
> >> elsewhere that are preventing a clean build, but right now it doesn't look
> >> buildable at all.
> >> 
> >> Alan?
> >
> > The major problem I have with your patch is that all it does is sweep
> > a problem under the rug.  While it may fix a build breakage I doubt
> > that it actually improves anything for users.  For example, if I apply
> > your patch for a 32-bit --enable-targets=all binutils build, then
> > attempt to disassemble one of the bpf gas testsuite objects:
> >
> > $ ~/build/gas/all32/binutils/objdump -dr tmpdir/lddw.o
> > /home/alan/build/gas/all32/binutils/objdump: tmpdir/lddw.o: file format not recognized
> >
> > That's due to lack of the required support from bfd/elf64-bpf.c to
> > load bpf object files into BFD.
> 
> Could you please elaborate on that?
> 
> What is it in elf64-bpf.c that must be improved in order to support
> 32-bit --enable-targets=all binutils?

It isn't that elf64-bpf.c is missing something, it's that the entire
file is not built on a 32-bit host with --enable-targets=all and
without --enable-64-bit-bfd.

> > I think you'll find a similar result for the other targets your patch
> > touches, and not just with objdump but with everything else that uses
> > libbfd.
> >
> > There is also a minor problem with the patch in that it adds entries
> > to TARGET32_LIBOPCODES_CFILES without removing the corresponding
> > entries from TARGET64_LIBOPCODES_CFILES.  Similarly for the defines in
> > opcodes/disassemble.c.

-- 
Alan Modra
Australia Development Lab, IBM