build fails on systems where libatomic.so is provided by compiler-rt

[dylanaraps]

Version

v16.5.0

Platform

Linux desert 5.12.6 #14 SMP Thu Jul 8 23:57:15 EEST 2021 x86_64 GNU/Linux

Subsystem

No response

What steps will reproduce the bug?

1. Attempt to build nodejs in an environment without libatomic (where libatomic is provided by compiler-rt).
2. Build fails due to missing libatomic.

In this environment, no linker flags are needed as compiler-rt provides libatomic implicitly.

The following workaround is used to get builds working:

# When libatomic does not exist, remove the linker argument which tries to use it.
[ -r /usr/lib/libatomic.so ] || {
    sed 's/-latomic//' node.gyp > _ 
    mv -f _ node.gyp
}

How often does it reproduce? Is there a required condition?

This is always reproducible in an environment without libatomic (where libatomic is provided by compiler-rt).

What is the expected behavior?

The build succeeds and libatomic is not linked when unneeded.

What do you see instead?

The build attempts to link to libatomic and fails due to the library not existing in the filesystem. The library is provided by compiler-rt in this environment.

Additional information

No response

[gireeshpunathil]

@dylanaraps - is there a better way to qualify systems without libatomic.so ? Is it

• a specific type of OS
• a specific OS configuration
• a specific user configuration

Also if you are planning to contribute, here is an example of how to do this in node.gyp in a more natural way: #30099

[dylanaraps]

It's hard to say. This is rather niche. It's a Linux distribution using LLVM/Clang (and no GNU components; gcc, binutils, etc).
LLVM provides libatomic via compiler-rt implicitly. (https://github.com/wyvertux/wyverkiss)

The environment can be detected like this:

• If toolchain is LLVM/Clang and compiler-rt is available and libatomic is not available

[targos]

With which options do you run the configure script?

[dylanaraps]

  ./configure \
      --shared-zlib \
      --shared-openssl \
      --with-intl=none \
      --without-etw \
      --without-dtrace \
      --without-report \
      --without-node-snapshot \
      --without-node-code-cache \ 
      --ninja

[dylanaraps]

Basically, the build system assumes that libatomic is always available on Linux. Problem is that LLVM + compiler-rt can be used to create an environment contrary to this assumption (where libatomic is implicitly provided by compiler-rt). Does this explain things better?

Expected behavior would be some kind of detection of this environment (and for the linker flag -latomic to not be passed).

[konimex]

One might ask, how do we detect if $CC is using libatomic or compiler-rt?

There's no good way (aside of $CC -print-file-name=libatomic.so, but this only checks if the file exists) but the next best thing would be detecting libgcc_s and compiler-rt, since compiler-rt replaces both libatomic and libgcc_s in an LLVM-only env. (And I don't think GCC can be built without libatomic since I think it's essential, but it's outside my knowledge realm at this point). So we can detect it by using $CC -print-libgcc-file-name. GCC (and Clang in a GCC env) will detect /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/11.1.0/libgcc.a, but Clang in an LLVM-only env will detect /usr/lib/clang/12.0.1/lib/linux/libclang_rt.builtins-x86_64.a

[targos]

Is there prior art of such detection in other projects? Maybe cpython?

[targos]

@nodejs/build-files

[williamh]

Hi, I am the packager of nodejs for Gentoo Linux.
This is an issue for us reported here.
As you can see from the bug report, we have a hack in place for nodejs 18 to get around it, but this is a patch I would like to get rid of at some point.
What can I do to assist with fixing this in the nodejs build system?

Thanks,

William

[bnoordhuis]

Untested, but as libatomic is only needed on some architectures, the diff below probably sidesteps the issue for x86_64:

diff --git a/node.gyp b/node.gyp
index 8fe89d8b1bc..12204cb2f60 100644
--- a/node.gyp
+++ b/node.gyp
@@ -115,7 +115,9 @@
           '-Wl,-bnoerrmsg',
         ],
       }],
-      ['OS == "linux" and llvm_version != "0.0"', {
+      ['OS == "linux" and '
+       'llvm_version != "0.0" and '
+       'target_arch in "arm loong64 mips mips64 mips64el mipsel ppc riscv64"', {
         'libraries': ['-latomic'],
       }],
     ],

LMK if that works for you and I'll turn it into a pull request.

[nvinson]

LMK if that works for you and I'll turn it into a pull request.

I just tried it and it still failed with

ld.lld: error: undefined symbol: __atomic_is_lock_free

Github has already linked to the ebuild & support files I used to test with, but I am posting the output of emerge --info below. A lot of the information is Gentoo specific, but it should still have diagnostic value here.

Portage 3.0.36 (python 3.10.7-final-0, default/linux/amd64/17.1/desktop, gcc-12.2.0, glibc-2.35-r8, 5.18.14-gentoo x86_64)
=================================================================
System uname: Linux-5.18.14-gentoo-x86_64-Intel-R-_Core-TM-_i7-4771_CPU_@_3.50GHz-with-glibc2.35
KiB Mem:    32557860 total,  10730172 free
KiB Swap:    2097148 total,   2015500 free
Timestamp of repository gentoo: Thu, 15 Sep 2022 21:31:46 +0000
Head commit of repository gentoo: 9eab52df292dba4d871398c81edab3437ffa2576

Timestamp of repository brother-overlay: Mon, 12 Sep 2022 19:25:29 +0000
Head commit of repository brother-overlay: d9faa8af87d81688313b3e308849f82642b7c437

Head commit of repository magpie: 0cc95ac94b4f616ee68011c724a1cdaa284c4748

sh bash 5.1_p16-r2
ld GNU ld (Gentoo 2.39 p4) 2.39.0
app-misc/pax-utils:        1.3.5::gentoo
app-shells/bash:           5.1_p16-r2::gentoo
dev-java/java-config:      2.3.1::gentoo
dev-lang/perl:             5.36.0::gentoo
dev-lang/python:           3.10.7::gentoo, 3.11.0_rc2::gentoo
dev-lang/rust:             1.62.1::gentoo
dev-util/cmake:            3.24.1::gentoo
dev-util/meson:            0.63.2-r1::gentoo
sys-apps/baselayout:       2.8-r2::gentoo
sys-apps/openrc:           0.45.2::gentoo
sys-apps/sandbox:          2.29::gentoo
sys-devel/autoconf:        2.13-r2::gentoo, 2.69-r6::gentoo, 2.71-r2::gentoo
sys-devel/automake:        1.16.5::gentoo
sys-devel/binutils:        2.39-r2::gentoo
sys-devel/binutils-config: 5.4.1::gentoo
sys-devel/clang:           14.0.6-r1::gentoo
sys-devel/gcc:             12.2.0::gentoo
sys-devel/gcc-config:      2.5-r1::gentoo
sys-devel/libtool:         2.4.7::gentoo
sys-devel/lld:             14.0.6::gentoo
sys-devel/llvm:            14.0.6-r2::gentoo
sys-devel/make:            4.3::gentoo
sys-kernel/linux-headers:  5.19::gentoo (virtual/os-headers)
sys-libs/glibc:            2.35-r8::gentoo
Repositories:

gentoo
    location: /var/db/repos/gentoo
    sync-type: git
    sync-uri: https://github.com/gentoo-mirror/gentoo.git
    priority: -1000
    sync-git-verify-commit-signature: true

brother-overlay
    location: /var/db/repos/brother-overlay
    sync-type: git
    sync-uri: https://github.com/gentoo-mirror/brother-overlay.git
    masters: gentoo

magpie
    location: /var/db/repos/magpie
    sync-type: git
    sync-uri: https://github.com/nvinson/magpie.git
    masters: gentoo

ACCEPT_KEYWORDS="amd64 ~amd64"
ACCEPT_LICENSE="* -@EULA"
AR="llvm-ar"
CBUILD="x86_64-pc-linux-gnu"
CC="clang"
CFLAGS="-march=native -O2 -pipe -D_FORTIFY_SOURCE=3 -fstack-protector-strong -flto=thin"
CHOST="x86_64-pc-linux-gnu"
CONFIG_PROTECT="/etc /opt/brother/scanner/brscan4/brsanenetdevice4.cfg /usr/share/gnupg/qualified.txt"
CONFIG_PROTECT_MASK="/etc/ca-certificates.conf /etc/dconf /etc/env.d /etc/fonts/fonts.conf /etc/gconf /etc/gentoo-release /etc/revdep-rebuild /etc/sandbox.d /etc/terminfo /etc/texmf/language.dat.d /etc/texmf/language.def.d /etc/texmf/updmap.d /etc/texmf/web2c"
CXX="clang++"
CXXFLAGS="-march=native -O2 -pipe -D_FORTIFY_SOURCE=3 -fstack-protector-strong -flto=thin"
DISTDIR="/var/cache/portage/distfiles"
EMERGE_DEFAULT_OPTS="--quiet-build"
ENV_UNSET="CARGO_HOME DBUS_SESSION_BUS_ADDRESS DISPLAY GOBIN GOPATH PERL5LIB PERL5OPT PERLPREFIX PERL_CORE PERL_MB_OPT PERL_MM_OPT XAUTHORITY XDG_CACHE_HOME XDG_CONFIG_HOME XDG_DATA_HOME XDG_RUNTIME_DIR"
FCFLAGS="-march=native -O2 -pipe"
FEATURES="assume-digests binpkg-docompress binpkg-dostrip binpkg-logs binpkg-multi-instance buildpkg-live config-protect-if-modified distlocks ebuild-locks fixlafiles ipc-sandbox merge-sync multilib-strict network-sandbox news parallel-fetch pid-sandbox preserve-libs protect-owned qa-unresolved-soname-deps sandbox sfperms strict unknown-features-warn unmerge-logs unmerge-orphans userfetch userpriv usersandbox usersync xattr"
FFLAGS="-march=native -O2 -pipe"
GENTOO_MIRRORS="http://distfiles.gentoo.org"
LANG="en_US.utf8"
LDFLAGS="-Wl,-O1 -Wl,--as-needed -fuse-ld=lld -rtlib=compiler-rt -unwindlib=libunwind"
MAKEOPTS="-j8"
NM="llvm-nm"
PKGDIR="/var/cache/binpkgs"
PORTAGE_CONFIGROOT="/"
PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --omit-dir-times --compress --force --whole-file --delete --stats --human-readable --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages --exclude=/.git"
PORTAGE_TMPDIR="/var/tmp"
RANLIB="llvm-ranlib"
SHELL="/bin/zsh"
USE="X a52 aac acl acpi alsa amd64 branding bzip2 cairo cdda cdr clang cleartype cli corefonts crypt cups dbus dri dts dvd dvdr elogind encode exif flac fortran gdbm gif glamor gpm gtk gui iconv icu ipv6 jpeg lcms libglvnd libnotify libtirpc mad mng mp3 mp4 mpeg multilib ncurses nls nptl ogg opengl openmp pam pango pcre pdf png policykit ppds qt5 readline sdl seccomp spell split-usr ssl startup-notification svg theora tiff truetype udev udisks unicode upower usb vaapi vorbis vpx wxwidgets x264 xattr xcb xml xv xvid zlib" ABI_X86="64" ADA_TARGET="gnat_2020" APACHE2_MODULES="authn_core authz_core socache_shmcb unixd actions alias auth_basic authn_alias authn_anon authn_dbm authn_default authn_file authz_dbm authz_default authz_groupfile authz_host authz_owner authz_user autoindex cache cgi cgid dav dav_fs dav_lock deflate dir disk_cache env expires ext_filter file_cache filter headers include info log_config logio mem_cache mime mime_magic negotiation rewrite setenvif speling status unique_id userdir usertrack vhost_alias" CALLIGRA_FEATURES="karbon sheets words" COLLECTD_PLUGINS="df interface irq load memory rrdtool swap syslog" CPU_FLAGS_X86="aes avx avx2 fma3 mmx mmxext popcnt sse sse2 sse3 sse4 sse4_1 sse4_2 ssse3" ELIBC="glibc" GPSD_PROTOCOLS="ashtech aivdm earthmate evermore fv18 garmin garmintxt gpsclock greis isync itrax mtk3301 nmea ntrip navcom oceanserver oldstyle oncore rtcm104v2 rtcm104v3 sirf skytraq superstar2 timing tsip tripmate tnt ublox ubx" INPUT_DEVICES="libinput" KERNEL="linux" L10N="en-US en" LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb ncurses text" LIBREOFFICE_EXTENSIONS="presenter-console presenter-minimizer" LUA_SINGLE_TARGET="lua5-1" LUA_TARGETS="lua5-1" OFFICE_IMPLEMENTATION="libreoffice" PHP_TARGETS="php7-4 php8-0" POSTGRES_TARGETS="postgres12 postgres13" PYTHON_SINGLE_TARGET="python3_10" PYTHON_TARGETS="python3_10" RUBY_TARGETS="ruby27" USERLAND="GNU" VIDEO_CARDS="intel i965" XTABLES_ADDONS="quota2 psd pknock lscan length2 ipv4options ipset ipp2p iface geoip fuzzy condition tee tarpit sysrq proto steal rawnat logmark ipmark dhcpmac delude chaos account"
Unset:  ADDR2LINE, ARFLAGS, AS, ASFLAGS, CCLD, CONFIG_SHELL, CPP, CPPFLAGS, CTARGET, CXXFILT, ELFEDIT, EXTRA_ECONF, F77FLAGS, FC, GCOV, GPROF, INSTALL_MASK, LC_ALL, LD, LEX, LFLAGS, LIBTOOL, LINGUAS, MAKE, MAKEFLAGS, OBJCOPY, OBJDUMP, PORTAGE_BINHOST, PORTAGE_BUNZIP2_COMMAND, PORTAGE_COMPRESS, PORTAGE_COMPRESS_FLAGS, PORTAGE_RSYNC_EXTRA_OPTS, READELF, RUSTFLAGS, SIZE, STRINGS, STRIP, YACC, YFLAGS

[bnoordhuis]

ld.lld: error: undefined symbol: __atomic_is_lock_free

https://reviews.llvm.org/D85044?id=287068 - looks like compiler-rt does not implement it at the time of writing. Guess that means it's not a drop-in replacement for libatomic yet.