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From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Thu, 8 Jul 2021 18:27:41 -0700
Message-ID: <CAMe9rOrcsNFVdHd+_R9=0M+tZFJf8c-Cpq+tT5mNBz=dSrHf2g@mail.gmail.com>
Subject: Re: [PATCH] x86_64: Remove unneeded static PIE check for undefined
 weak diagnostic
To: Fangrui Song <maskray@google.com>, 
 Libc-stable Mailing List <libc-stable@sourceware.org>
Cc: GNU C Library <libc-alpha@sourceware.org>
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On Thu, Jul 8, 2021 at 1:09 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Thu, Jul 8, 2021 at 12:51 PM Fangrui Song via Libc-alpha
> <libc-alpha@sourceware.org> wrote:
> >
> > https://sourceware.org/bugzilla/show_bug.cgi?id=21782 dropped an ld
> > diagnostic for R_X86_64_PC32 referencing an undefined weak symbol in
> > -pie links.  Arguably keeping the diagnostic like other ports is more
> > correct, since statically resolving movl foo(%rip), %eax to the
> > link-time zero address produces a corrupted output.
> >
> > It turns out that --enable-static-pie builds do not depend on the ld
> > behavior. GCC generates GOT indirection for weak declarations for
> > -fPIE/-fPIC, so what ld does with the PC-relative relocation doesn't
> > really matter. I confirmed the argument with a --enable-static-pie build
> > with trunk LLD, whose -pie mode reports an error for `.weak foo; movl
> > foo(%rip), %eax`
> > (https://sourceware.org/bugzilla/show_bug.cgi?id=21782#c6
>
> I agree that
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=21782
>
> was a false alarm for static PIE.  This linker check isn't necessary.
>
> The patch is OK.
>
> Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
>

Please backlport it to release branches.   Otherwise binutils 2.37 can't
build them.

Thanks.

-- 
H.J.