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

["H.J. Lu via Libc-alpha" <libc-alpha@sourceware.org>]

On Thu, Aug 5, 2021 at 9:29 AM Fangrui Song via Libc-alpha
<libc-alpha@sourceware.org> 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).

This is an lld bug, similar to:

https://sourceware.org/bugzilla/show_bug.cgi?id=13302

Please fix it at least on x86.

> 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(-)
>
> diff --git a/configure b/configure
> index 9b966196d4..050f1a29cf 100755
> --- a/configure
> +++ b/configure
> @@ -4664,9 +4664,10 @@ if test $ac_verc_fail = yes; then
>  fi
>
>
> -if test -n "`$LD --version | sed -n 's/^GNU \(gold\).*$/\1/p'`"; then
> +case $($LD --version) in
> +  "GNU gold"*)
>    # Accept gold 1.14 or higher
> -  for ac_prog in $LD
> +    for ac_prog in $LD
>  do
>    # Extract the first word of "$ac_prog", so it can be a program name with args.
>  set dummy $ac_prog; ac_word=$2
> @@ -4729,8 +4730,75 @@ if test $ac_verc_fail = yes; then
>    LD=: critic_missing="$critic_missing GNU gold"
>  fi
>
> +    ;;
> +  "LLD"*)
> +  # Accept LLD 13.0.0 or higher
> +    for ac_prog in $LD
> +do
> +  # Extract the first word of "$ac_prog", so it can be a program name with args.
> +set dummy $ac_prog; ac_word=$2
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
> +$as_echo_n "checking for $ac_word... " >&6; }
> +if ${ac_cv_prog_LD+:} false; then :
> +  $as_echo_n "(cached) " >&6
>  else
> -  for ac_prog in $LD
> +  if test -n "$LD"; then
> +  ac_cv_prog_LD="$LD" # Let the user override the test.
> +else
> +as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
> +for as_dir in $PATH
> +do
> +  IFS=$as_save_IFS
> +  test -z "$as_dir" && as_dir=.
> +    for ac_exec_ext in '' $ac_executable_extensions; do
> +  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
> +    ac_cv_prog_LD="$ac_prog"
> +    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
> +    break 2
> +  fi
> +done
> +  done
> +IFS=$as_save_IFS
> +
> +fi
> +fi
> +LD=$ac_cv_prog_LD
> +if test -n "$LD"; then
> +  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $LD" >&5
> +$as_echo "$LD" >&6; }
> +else
> +  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
> +$as_echo "no" >&6; }
> +fi
> +
> +
> +  test -n "$LD" && break
> +done
> +
> +if test -z "$LD"; then
> +  ac_verc_fail=yes
> +else
> +  # Found it, now check the version.
> +  { $as_echo "$as_me:${as_lineno-$LINENO}: checking version of $LD" >&5
> +$as_echo_n "checking version of $LD... " >&6; }
> +  ac_prog_version=`$LD --version 2>&1 | sed -n 's/^.*LLD.* \([0-9][0-9]*\.[0-9.]*\).*$/\1/p'`
> +  case $ac_prog_version in
> +    '') ac_prog_version="v. ?.??, bad"; ac_verc_fail=yes;;
> +    1[3-9].*|[2-9][0-9].*)
> +       ac_prog_version="$ac_prog_version, ok"; ac_verc_fail=no;;
> +    *) ac_prog_version="$ac_prog_version, bad"; ac_verc_fail=yes;;
> +
> +  esac
> +  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_prog_version" >&5
> +$as_echo "$ac_prog_version" >&6; }
> +fi
> +if test $ac_verc_fail = yes; then
> +  LD=: critic_missing="$critic_missing LLD"
> +fi
> +
> +    ;;
> +  *)
> +    for ac_prog in $LD
>  do
>    # Extract the first word of "$ac_prog", so it can be a program name with args.
>  set dummy $ac_prog; ac_word=$2
> @@ -4793,7 +4861,8 @@ if test $ac_verc_fail = yes; then
>    LD=: critic_missing="$critic_missing GNU ld"
>  fi
>
> -fi
> +    ;;
> +esac
>
>  # These programs are version sensitive.
>  for ac_prog in gnumake gmake make
> diff --git a/configure.ac b/configure.ac
> index 17a4c9a1ab..5632277f9c 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -995,18 +995,28 @@ AC_CHECK_PROG_VER(AS, $AS, --version,
>                   [2.1[0-9][0-9]*|2.2[5-9]*|2.[3-9][0-9]*|[3-9].*|[1-9][0-9]*],
>                   AS=: critic_missing="$critic_missing as")
>
> -if test -n "`$LD --version | sed -n 's/^GNU \(gold\).*$/\1/p'`"; then
> +case $($LD --version) in
> +  "GNU gold"*)
>    # Accept gold 1.14 or higher
> -  AC_CHECK_PROG_VER(LD, $LD, --version,
> +    AC_CHECK_PROG_VER(LD, $LD, --version,
>                     [GNU gold.* \([0-9][0-9]*\.[0-9.]*\)],
>                     [1.1[4-9]*|1.[2-9][0-9]*|1.1[0-9][0-9]*|[2-9].*|[1-9][0-9]*],
>                     LD=: critic_missing="$critic_missing GNU gold")
> -else
> -  AC_CHECK_PROG_VER(LD, $LD, --version,
> +    ;;
> +  "LLD"*)
> +  # Accept LLD 13.0.0 or higher
> +    AC_CHECK_PROG_VER(LD, $LD, --version,
> +                   [LLD.* \([0-9][0-9]*\.[0-9.]*\)],
> +                   [1[3-9].*|[2-9][0-9].*],
> +                   LD=: critic_missing="$critic_missing LLD")
> +    ;;
> +  *)
> +    AC_CHECK_PROG_VER(LD, $LD, --version,
>                     [GNU ld.* \([0-9][0-9]*\.[0-9.]*\)],
>                     [2.1[0-9][0-9]*|2.2[5-9]*|2.[3-9][0-9]*|[3-9].*|[1-9][0-9]*],
>                     LD=: critic_missing="$critic_missing GNU ld")
> -fi
> +    ;;
> +esac
>
>  # These programs are version sensitive.
>  AC_CHECK_PROG_VER(MAKE, gnumake gmake make, --version,
> --
> 2.32.0.605.g8dce9f2422-goog
>


-- 
H.J.