Does glibc now compile with mold?

[immolo]

I see glibc has been removed from gdoc tracker but I'm still unable to get this build with the following error:

`checking if x86_64-pc-linux-gnu-gcc -m32 -mstackrealign -march=native -pipe -O2 -fuse-ld=mold -Wl,-O1 -Wl,--as-needed is sufficient to build libc... yes
checking for i686-pc-linux-gnu-nm... x86_64-pc-linux-gnu-nm
checking for python3... python3
checking version of python3... 3.11.0, ok
configure: error:
*** These critical programs are missing or too old: GNU ld
*** Check the INSTALL file for required versions.

• ERROR: sys-libs/glibc-2.36-r4::gentoo failed (configure phase):
• failed to configure glibc`

Am I missing something or was the line just removed in error?

[ghost]

If glibc devs does not add support for mold it would be hard to build, as it's not something @rui314 can do on his side

[ghost]

I have the same problem as well

[rui314]

I believe the glibc's configure script not only checks if the linker is GNU ld but also which version it is. To simulate GNU ld, we include the phrase "compatible with GNU ld" in our --help message (as I discussed in my essay on software compatibility and our user-agent problem, which can be found at https://www.sigbus.info/software-compatibility-and-our-own-user-agent-problem). However, it's possible that glibc may verify the version as well. You may want to ask glibc devs to remove excessive version checks.

[SigHunter]

just as an update: this is still the case for current glibc 2.38

[satmandu]

Looking at https://github.com/bminor/glibc/blob/master/configure.ac :

# Accept binutils 2.25 or newer.
libc_cv_with_lld=no
case $($LD --version) in
  "GNU gold"*)
  # Accept gold 1.14 or higher
    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")
    ;;
  "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")
    libc_cv_with_lld=yes
    ;;
  *)
    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="$critic_missing GNU ld")
    ;;
esac
LIBC_CONFIG_VAR([with-lld], [$libc_cv_with_lld])

Note that all of these matches expect to match the beginning of the line, and this doesn't work for matching mold because it only searches for the version number after matching the text GNU ld.

The third fallthrough option works for ld as per the resultant regex in https://github.com/bminor/glibc/blob/master/configure :

ld --version
GNU ld (Chromebrew) 2.44
Copyright (C) 2025 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or (at your option) a later version.
This program has absolutely no warranty.
ld --version 2>&1 | sed -n 's/^.*GNU ld.* \([0-9][0-9]*\.[0-9.]*\).*$/\1/p'
2.44

However, this doesn't work for mold:

mold --version
mold 2.37.1 (32c8f6dd61e4b6bb92436eb67a54e22b48b54f1f; compatible with GNU ld)
mold --version 2>&1 | sed -n 's/^.*GNU ld.* \([0-9][0-9]*\.[0-9.]*\).*$/\1/p'

Something like this might work:

# Accept binutils 2.25 or newer.
libc_cv_with_lld=no
case $($LD --version) in
  "GNU gold"*)
  # Accept gold 1.14 or higher
    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")
    ;;
  "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")
    libc_cv_with_lld=yes
    ;;
  "mold"*)
  # Accept mold 2.37.1 or higher
    AC_CHECK_PROG_VER(LD, $LD, --version,
		    [mold.* \([0-9][0-9]*\.[0-9.]*\)],
		    [2.37[1-9]*|2.3[8-9][0-9]*|2.[4-9][0-9]*],
		    LD=: critic_missing="$critic_missing mold")
    ;;
  *)
    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="$critic_missing GNU ld")
    ;;
esac
LIBC_CONFIG_VAR([with-lld], [$libc_cv_with_lld])

Alternately, mold --version could be modified to spit out version again at the end, i.e., mold 2.37.1 (32c8f6dd61e4b6bb92436eb67a54e22b48b54f1f; compatible with GNU ld 2.37.1), as that does work with the default regex:

echo "mold 2.37.1 (32c8f6dd61e4b6bb92436eb67a54e22b48b54f1f; compatible with GNU ld 2.37.1)" | sed -n 's/^.*GNU ld.* \([0-9][0-9]*\.[0-9.]*\).*$/\1/p'
2.37.1