[llvm-dev] Should we switch to --hash-style=both by default in LLD ?

[Rui Ueyama via llvm-dev]

On Mon, Oct 2, 2017 at 3:33 PM, Romain GEISSLER <romain.geissler at amadeus.com
> wrote:

>
> > Le 3 oct. 2017 à 00:09, Rui Ueyama <ruiu at google.com> a écrit :
> >
> > I read through the binutils mailing list thread, but I couldn't find the
> exact reason why making --hash-style=gnu default except MIPS wasn't a good
> idea.Do you mind if I ask you to explain it again for me?
> >
> > Since lld is a new linker, we could make a bit more radical change than
> GNU ld can do, so I wonder if --hash-style=both is the right choice for us.
>
> To be honest, I have no idea. I am much more on the user side of
> ld.bfd/ld.gold than the developer side. I know very little about the exact
> specific ELF ABI Michael Matz is referring to. I actually would expect you
> lld developers to have quite an good knowledge of it ;)
>

There are old systems that do not support .gnu.hash sections, but among the
systems lld support, I believe we can enable --hash-style=gnu except MIPS.


> On my side, I do configure and/or patch all my linkers (bfd, gold and lld)
> to use the "gnu" hash-style by default, and I can only say that with a
> classical glibc environment, it works. The fact that some Linux distro are
> doing that too seems to be a good arguments that it is safe, at least when
> using glibc. The question is more whether lld seeks (size) optimization
> over correctness (wrt the ELF specification) ?
>

I believe .hash section is optional, so an executable only with .gnu.hash
is still valid in terms of the ELF specification even on a system that
doesn't recognize .gnu.hash.

So, maybe making --hash-style=gnu a default option except MIPS is a
reasonable choice for us? Any objection?
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