Re: [PATCH] configure: Replace -Wl,-r,-d with -Wl,-r

[Fāng-ruì Sòng]

On Fri, Feb 11, 2022 at 6:04 AM Daniel Kiper <dkiper@net-space.pl> wrote:
>
> On Tue, Feb 08, 2022 at 03:25:27PM -0800, Fangrui Song via Grub-devel wrote:
> > In GNU ld and ld.lld, -d is used with -r to allocate space to COMMON 
> > symbols.
> > This behavior is presumably to work around legacy projects which inspect
> > relocatable output by themselves and do not handle COMMON symbols. grub does
> > not do this.
> >
> > See https://github.com/llvm/llvm-project/issues/53660
> > -d is quite useless and ld.lld may remove -d or make it a no-op for the
> > 15.0.0 release.
> > ---
> >  acinclude.m4                |  2 +-
> >  conf/Makefile.common        |  2 +-
> >  grub-core/Makefile.core.def | 20 ++++++++++----------
> >  grub-core/genmod.sh.in      |  4 ++--
> >  4 files changed, 14 insertions(+), 14 deletions(-)
> >
> > diff --git a/acinclude.m4 b/acinclude.m4
> > index 6e14bb553..fa7840f09 100644
> > --- a/acinclude.m4
> > +++ b/acinclude.m4
> > @@ -430,7 +430,7 @@ link_nopie_needed=no]
> >  AC_MSG_CHECKING([whether linker needs disabling of PIE to work])
> >  AC_LANG_CONFTEST([AC_LANG_SOURCE([[]])])
> >
> > -[if eval "$ac_compile -Wl,-r,-d -nostdlib -Werror -o conftest.o" 2> 
> > /dev/null; then]
> > +[if eval "$ac_compile -Wl,-r -nostdlib -Werror -o conftest.o" 2> 
> > /dev/null; then]
>
> It looks that these changes do not break any builds. So, I am OK with
> them. Though should not we add -fno-common to the CFLAGS too, e.g.:
>
> diff --git a/configure.ac b/configure.ac
> index 5c01af0fa..d1eaafee1 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -85,9 +85,9 @@ fi
>
>  # Enable support for "restrict" keyword and other
>  # features from gnu99 C language standard.
> -BUILD_CFLAGS="-std=gnu99 $BUILD_CFLAGS"
> -HOST_CFLAGS="-std=gnu99 $HOST_CFLAGS"
> -TARGET_CFLAGS="-std=gnu99 $TARGET_CFLAGS"
> +BUILD_CFLAGS="-std=gnu99 -fno-common $BUILD_CFLAGS"
> +HOST_CFLAGS="-std=gnu99 -fno-common $HOST_CFLAGS"
> +TARGET_CFLAGS="-std=gnu99 -fno-common $TARGET_CFLAGS"
>
>  # Default HOST_CPPFLAGS
>  HOST_CPPFLAGS="$HOST_CPPFLAGS -Wall -W"
>
> Daniel

Adding -fno-common to ensure no COMMON symbol will also be a good idea.
Are you making the change? :)