[llvm-dev] Targeting old glibc

[Alexandre Bique via llvm-dev]

On Mon, Nov 9, 2020 at 6:52 PM Fāng-ruì Sòng <maskray at google.com> wrote:
> Recent libm.a and libm.so are actually linker scripts
>
> % cat /usr/lib/x86_64-linux-gnu/libm.a
> /* GNU ld script
> */
> OUTPUT_FORMAT(elf64-x86-64)
> GROUP ( /usr/lib/x86_64-linux-gnu/libm-2.31.a
> /usr/lib/x86_64-linux-gnu/libmvec.a )
> % cat /usr/lib/x86_64-linux-gnu/libm.so
> /* GNU ld script
> */
> OUTPUT_FORMAT(elf64-x86-64)
> GROUP ( /lib/x86_64-linux-gnu/libm.so.6  AS_NEEDED (
> /lib/x86_64-linux-gnu/libmvec.so.1 ) )

In this script the libmvec is mentioned as "AS_NEEDED", and it is not
needed in my case, yet lld pulls its dependency toward exp at GLIBC_2.29.

Is it a bug in lld?

Regards,
Alexandre