Re: [PATCH v2 3/3] configure: Allow LD to be LLD 13.0.0 or above [BZ #26558]

["Fāng-ruì Sòng via Libc-alpha" <libc-alpha@sourceware.org>]

On Tue, Aug 10, 2021 at 3:19 PM Fangrui Song <maskray@google.com> wrote:
>
> On 2021-08-05, Fangrui Song wrote:
> >When using LLD (LLVM linker) as the linker, configure prints a confusing
> >message.
> >
> >    *** These critical programs are missing or too old: GNU ld
> >
> >LLD>=13.0.0 can build glibc --enable-static-pie. (8.0.0 needs one
> >workaround for -Wl,-defsym=_begin=0. 9.0.0 works with
> >--disable-static-pie).
> >
> >With BZ #28153 (glibc bug exposed by testing with LLD) fixed,
> >`make check` only has 2 more failures with LLD than with GNU ld:
> >BZ #28154 (LLD follows the PowerPC port of GNU ld for ifunc by
> >placing IRELATIVE relocations in .rela.dyn).
> >The set of dynamic symbols is the same with GNU ld and LLD,
> >modulo unused SHN_ABS version node symbols.
> >
> >For comparison, gold does not support --enable-static-pie
> >yet (--no-dynamic-linker is unsupported BZ #22221), yet
> >has 6 failures more than LLD. gold linked libc.so has
> >larger .dynsym differences with GNU ld and LLD
> >(ISTM non-default version symbols are changed to default versions
> >by a version script).
> >
> >---
> >
> >I identified the lack of support of
> >
> >* version script on non-default version symbols
> >* copy relocations on non-default version symbols
> >
> >in an earlier snapshot of LLD 13.0.0 and fixed them.
> >The functionality of the LLD linked libc.so and ld.so looks pretty good.
> >---
> > configure    | 77 +++++++++++++++++++++++++++++++++++++++++++++++++---
> > configure.ac | 20 ++++++++++----
> > 2 files changed, 88 insertions(+), 9 deletions(-)
>
> Ping:)
>
> (The code/test hasn't been changed since v1.
>   v2 just added BZ numbers.)
>
> x86-64 only 2 more ifunc FAIL which tickle some weak point of ifunc implementation.
>
> aarch64 `make-check` is fully on par with GNU ld.
>    (https://sourceware.org/pipermail/libc-alpha/2021-August/130040.html)

Ping^2

("elf: Replace .tls_common with .tbss definition [BZ #28152]" has been
subsumed into a tls-macros.h removal patch.)