llvmPackages.clangUseLLVM cannot find libunwind.so

[SharzyL]

Describe the bug

When using llvmPackages.clangUseLLVM to compile, the linker cannot find libunwind.so.

Steps To Reproduce

Steps to reproduce the behavior:

$ echo "int main() { }" > a.c
$ nix shell nixpkgs#llvmPackages.clangUseLLVM -c clang /tmp/a.c
/nix/store/039g378vc3pc3dvi9dzdlrd0i4q93qwf-binutils-2.39/bin/ld: cannot find -l:libunwind.so: No such file or directory
clang-11: error: linker command failed with exit code 1 (use -v to see invocation)

Expected behavior

The linker should be able to find libunwind and compile successfully.

Additional context

Run with NIX_DEBUG=1 gives the following:

$ NIX_DEBUG=1 nix shell nixpkgs#llvmPackages.clangUseLLVM -c clang a.c
HARDENING: disabled flags: pie pic format stackprotector fortify strictoverflow
extra flags before to /nix/store/39yzdj9a7l8aw317l8la4kp6aalczsq7-clang-11.1.0/bin/clang:
  -Wl\,-dynamic-linker=/nix/store/4nlgxhb09sdr51nc9hdm8az5b08vzkgx-glibc-2.35-163/lib/ld-linux-x86-64.so.2
  -target
  x86_64-unknown-linux-gnu
original flags to /nix/store/39yzdj9a7l8aw317l8la4kp6aalczsq7-clang-11.1.0/bin/clang:
  a.c
extra flags after to /nix/store/39yzdj9a7l8aw317l8la4kp6aalczsq7-clang-11.1.0/bin/clang:
  -B/nix/store/4nlgxhb09sdr51nc9hdm8az5b08vzkgx-glibc-2.35-163/lib/
  -idirafter
  /nix/store/4pqv2mwdn88h7xvsm7a5zplrd8sxzvw0-glibc-2.35-163-dev/include
  --gcc-toolchain=/nix/store/1gf2flfqnpqbr1b4p4qz2f72y42bs56r-gcc-11.3.0
  -B/nix/store/fbc6m1s0638pf3vk5wgmcsbap8f04nar-clang-11.1.0-lib/lib
  -rtlib=compiler-rt
  -Wno-unused-command-line-argument
  -B/nix/store/lkckixdqkvwscdr5jf0v07w77lhlm70f-compiler-rt-libc-11.1.0/lib
  --unwindlib=libunwind
  -resource-dir=/nix/store/6bmyzky9i7rd2dp3lxc47rlabrhcl46y-clang-wrapper-11.1.0/resource-root
  -B
  /nix/store/6bmyzky9i7rd2dp3lxc47rlabrhcl46y-clang-wrapper-11.1.0/resource-root/lib
  -B/nix/store/6bmyzky9i7rd2dp3lxc47rlabrhcl46y-clang-wrapper-11.1.0/bin/
  -L/nix/store/4nlgxhb09sdr51nc9hdm8az5b08vzkgx-glibc-2.35-163/lib
  -L/nix/store/fbc6m1s0638pf3vk5wgmcsbap8f04nar-clang-11.1.0-lib/lib
HARDENING: disabled flags: relro pie bindnow
extra flags before to /nix/store/039g378vc3pc3dvi9dzdlrd0i4q93qwf-binutils-2.39/bin/ld:
  ''
original flags to /nix/store/039g378vc3pc3dvi9dzdlrd0i4q93qwf-binutils-2.39/bin/ld:
  --eh-frame-hdr
  -m
  elf_x86_64
  -o
  a.out
  /nix/store/4nlgxhb09sdr51nc9hdm8az5b08vzkgx-glibc-2.35-163/lib/crt1.o
  /nix/store/4nlgxhb09sdr51nc9hdm8az5b08vzkgx-glibc-2.35-163/lib/crti.o
  /nix/store/6bmyzky9i7rd2dp3lxc47rlabrhcl46y-clang-wrapper-11.1.0/resource-root/lib/linux/clang_rt.crtbegin-x86_64.o
  -L/nix/store/4nlgxhb09sdr51nc9hdm8az5b08vzkgx-glibc-2.35-163/lib
  -L/nix/store/fbc6m1s0638pf3vk5wgmcsbap8f04nar-clang-11.1.0-lib/lib
  -L/nix/store/1gf2flfqnpqbr1b4p4qz2f72y42bs56r-gcc-11.3.0/lib64/gcc/x86_64-unknown-linux-gnu/11.3.0
  -L/nix/store/1gf2flfqnpqbr1b4p4qz2f72y42bs56r-gcc-11.3.0/lib64/gcc/x86_64-unknown-linux-gnu/11.3.0/../../../../lib64
  -L/nix/store/1gf2flfqnpqbr1b4p4qz2f72y42bs56r-gcc-11.3.0/lib64/gcc/x86_64-unknown-linux-gnu/11.3.0/../../..
  -dynamic-linker=/nix/store/4nlgxhb09sdr51nc9hdm8az5b08vzkgx-glibc-2.35-163/lib/ld-linux-x86-64.so.2
  /tmp/a-804f0d.o
  /nix/store/6bmyzky9i7rd2dp3lxc47rlabrhcl46y-clang-wrapper-11.1.0/resource-root/lib/linux/libclang_rt.builtins-x86_64.a
  --as-needed
  -l:libunwind.so
  --no-as-needed
  -lc
  /nix/store/6bmyzky9i7rd2dp3lxc47rlabrhcl46y-clang-wrapper-11.1.0/resource-root/lib/linux/libclang_rt.builtins-x86_64.a
  --as-needed
  -l:libunwind.so
  --no-as-needed
  /nix/store/6bmyzky9i7rd2dp3lxc47rlabrhcl46y-clang-wrapper-11.1.0/resource-root/lib/linux/clang_rt.crtend-x86_64.o
  /nix/store/4nlgxhb09sdr51nc9hdm8az5b08vzkgx-glibc-2.35-163/lib/crtn.o
extra flags after to /nix/store/039g378vc3pc3dvi9dzdlrd0i4q93qwf-binutils-2.39/bin/ld:
  -rpath
  /nix/store/4nlgxhb09sdr51nc9hdm8az5b08vzkgx-glibc-2.35-163/lib
/nix/store/039g378vc3pc3dvi9dzdlrd0i4q93qwf-binutils-2.39/bin/ld: cannot find -l:libunwind.so: No such file or directory
clang-11: error: linker command failed with exit code 1 (use -v to see invocation)

It is clear that the path of libunwind is not added to search path. Maybe we should add -L${targetLlvmLibraries.libunwind}/lib in nixSupport.cc-cflags.

nixpkgs/pkgs/development/compilers/llvm/git/default.nix

Lines 151 to 172 in 3a86856

	clangUseLLVM = wrapCCWith rec {
	cc = tools.clang-unwrapped;
	libcxx = targetLlvmLibraries.libcxx;
	bintools = bintools';
	extraPackages = [
	targetLlvmLibraries.libcxxabi
	targetLlvmLibraries.compiler-rt
	] ++ lib.optionals (!stdenv.targetPlatform.isWasm) [
	targetLlvmLibraries.libunwind
	];
	extraBuildCommands = mkExtraBuildCommands cc;
	nixSupport.cc-cflags =
	[ "-rtlib=compiler-rt"
	"-Wno-unused-command-line-argument"
	"-B${targetLlvmLibraries.compiler-rt}/lib"
	]
	++ lib.optional (!stdenv.targetPlatform.isWasm) "--unwindlib=libunwind"
	++ lib.optional
	(!stdenv.targetPlatform.isWasm && !stdenv.targetPlatform.isFreeBSD && stdenv.targetPlatform.useLLVM or false)
	"-lunwind"
	++ lib.optional stdenv.targetPlatform.isWasm "-fno-exceptions";
	};

Notify maintainers

@Ericson2314 @primeos

Metadata

• system: "x86_64-linux"
• host os: Linux 6.0.8, NixOS, 22.11 (Raccoon), 22.11pre-git
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.11.0
• channels(root): "nixos-22.05"
• channels(sharzy): "nixos, nixpkgs"
• nixpkgs: /home/sharzy/.nix-defexpr/channels/nixpkgs

[pwaller]

I agree with this fix. I think it the same treatment is also needed for libc++ and libstdc++?

[JustAnotherCodemonkey]

In spite of the PR, this is still an issue for me:

$ clang -fuse-ld=lld  test.c
ld.lld: error: unable to find library -lunwind
ld.lld: error: unable to find library -lunwind
clang-16: error: linker command failed with exit code 1 (use -v to see invocation)

[SharzyL]

In spite of the PR, this is still an issue for me:

$ clang -fuse-ld=lld  test.c
ld.lld: error: unable to find library -lunwind
ld.lld: error: unable to find library -lunwind
clang-16: error: linker command failed with exit code 1 (use -v to see invocation)

How to reproduce this?

[JustAnotherCodemonkey]

In spite of the PR, this is still an issue for me:

$ clang -fuse-ld=lld  test.c
ld.lld: error: unable to find library -lunwind
ld.lld: error: unable to find library -lunwind
clang-16: error: linker command failed with exit code 1 (use -v to see invocation)

How to reproduce this?

Have the following in your configuration.nix for your system packages:

clang-tools
llvmPackages.clangUseLLVM
llvmPackages.bintools

Clang a c file. It gives and error. Clang a c file with -fuse-ld=lld and it gives the above error

[SharzyL]

Have the following in your configuration.nix for your system packages:

clang-tools
llvmPackages.clangUseLLVM
llvmPackages.bintools

Clang a c file. It gives and error. Clang a c file with -fuse-ld=lld and it gives the above error

@JustAnotherCodemonkey Sorry but I failed to reproduce this, clang compiles without error on my machine. Could you provide the commit of your nixpkgs, the running platform, and a debug trace by running NIX_DEBUG=1 clang -fuse-ld=lld -v a.c.

[JustAnotherCodemonkey]

Have the following in your configuration.nix for your system packages:

clang-tools
llvmPackages.clangUseLLVM
llvmPackages.bintools

Clang a c file. It gives and error. Clang a c file with -fuse-ld=lld and it gives the above error

@JustAnotherCodemonkey Sorry but I failed to reproduce this, clang compiles without error on my machine. Could you provide the commit of your nixpkgs, the running platform, and a debug trace by running NIX_DEBUG=1 clang -fuse-ld=lld -v a.c.

@SharzyL

$ NIX_DEBUG=1 clang -fuse-ld=lld -v tester.c
HARDENING: disabled flags: pie pic format stackprotector fortify strictoverflow
extra flags before to /nix/store/pw7xsl0b4g7izz8hq2s5zkying2i7a4g-clang-16.0.6/bin/clang:
  -Wl\,-dynamic-linker=/nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib/ld-linux-x86-64.so.2
  -target
  x86_64-unknown-linux-gnu
original flags to /nix/store/pw7xsl0b4g7izz8hq2s5zkying2i7a4g-clang-16.0.6/bin/clang:
  -fuse-ld=lld
  -v
  tester.c
extra flags after to /nix/store/pw7xsl0b4g7izz8hq2s5zkying2i7a4g-clang-16.0.6/bin/clang:
  -B/nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib/
  -idirafter
  /nix/store/zzwrkd2n3blr2m5ydm6236kbisvldj73-glibc-2.38-44-dev/include
  --gcc-toolchain=/nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0
  -B/nix/store/nzfgg5hbc3v4qisqj0ah9wdrbfszgfin-clang-16.0.6-lib/lib
  -resource-dir=/nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root
  -rtlib=compiler-rt
  -Wno-unused-command-line-argument
  -B/nix/store/8yp6irxxi36xqdfshbqgssv37zcplafy-compiler-rt-libc-16.0.6/lib
  --unwindlib=libunwind
  -B/nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/bin/
  -L/nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib
  -L/nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0//lib
  -L/nix/store/l0ydz31lwa97zickpsxj2vmprcigh1m4-gcc-12.3.0-libgcc/lib
  -L/nix/store/nzfgg5hbc3v4qisqj0ah9wdrbfszgfin-clang-16.0.6-lib/lib
clang version 16.0.6
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /nix/store/pw7xsl0b4g7izz8hq2s5zkying2i7a4g-clang-16.0.6/bin
Found candidate GCC installation: /nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0/lib/gcc/x86_64-unknown-linux-gnu/12.3.0
Found candidate GCC installation: /nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0/lib64/gcc/x86_64-unknown-linux-gnu/12.3.0
Selected GCC installation: /nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0/lib64/gcc/x86_64-unknown-linux-gnu/12.3.0
Candidate multilib: .;@m64
Selected multilib: .;@m64
 "/nix/store/pw7xsl0b4g7izz8hq2s5zkying2i7a4g-clang-16.0.6/bin/clang-16" -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name tester.c -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=all -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -mllvm -treat-scalable-fixed-error-as-warning -debugger-tuning=gdb -v -fcoverage-compilation-dir=/home/sophiaw -nostdsysteminc -resource-dir /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root -idirafter /nix/store/zzwrkd2n3blr2m5ydm6236kbisvldj73-glibc-2.38-44-dev/include -internal-isystem /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root/include -Wno-unused-command-line-argument -fdebug-compilation-dir=/home/sophiaw -ferror-limit 19 -fgnuc-version=4.2.1 -fcolor-diagnostics -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/tester-d91761.o -x c tester.c
clang -cc1 version 16.0.6 based upon LLVM 16.0.6 default target x86_64-unknown-linux-gnu
#include "..." search starts here:
#include <...> search starts here:
 /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root/include
 /nix/store/zzwrkd2n3blr2m5ydm6236kbisvldj73-glibc-2.38-44-dev/include
End of search list.
 "/etc/profiles/per-user/sophiaw/bin/ld.lld" -pie --hash-style=gnu --eh-frame-hdr -m elf_x86_64 -o a.out /nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib/Scrt1.o /nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib/crti.o /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root/lib/linux/clang_rt.crtbegin-x86_64.o -L/nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib -L/nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0//lib -L/nix/store/l0ydz31lwa97zickpsxj2vmprcigh1m4-gcc-12.3.0-libgcc/lib -L/nix/store/nzfgg5hbc3v4qisqj0ah9wdrbfszgfin-clang-16.0.6-lib/lib -L/nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0/lib64/gcc/x86_64-unknown-linux-gnu/12.3.0 -L/nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0/lib64/gcc/x86_64-unknown-linux-gnu/12.3.0/../../../../lib64 -dynamic-linker=/nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib/ld-linux-x86-64.so.2 /tmp/tester-d91761.o /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root/lib/linux/libclang_rt.builtins-x86_64.a --as-needed -lunwind --no-as-needed -lc /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root/lib/linux/libclang_rt.builtins-x86_64.a --as-needed -lunwind --no-as-needed /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root/lib/linux/clang_rt.crtend-x86_64.o /nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib/crtn.o
HARDENING: disabled flags: relro pie bindnow
extra flags before to /nix/store/d6ini38wpv8f7ikkzj9bm15fqarfx9q5-llvm-binutils-16.0.6/bin/ld.lld:
  ''
original flags to /nix/store/d6ini38wpv8f7ikkzj9bm15fqarfx9q5-llvm-binutils-16.0.6/bin/ld.lld:
  -pie
  --hash-style=gnu
  --eh-frame-hdr
  -m
  elf_x86_64
  -o
  a.out
  /nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib/Scrt1.o
  /nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib/crti.o
  /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root/lib/linux/clang_rt.crtbegin-x86_64.o
  -L/nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib
  -L/nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0//lib
  -L/nix/store/l0ydz31lwa97zickpsxj2vmprcigh1m4-gcc-12.3.0-libgcc/lib
  -L/nix/store/nzfgg5hbc3v4qisqj0ah9wdrbfszgfin-clang-16.0.6-lib/lib
  -L/nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0/lib64/gcc/x86_64-unknown-linux-gnu/12.3.0
  -L/nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0/lib64/gcc/x86_64-unknown-linux-gnu/12.3.0/../../../../lib64
  -dynamic-linker=/nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib/ld-linux-x86-64.so.2
  /tmp/tester-d91761.o
  /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root/lib/linux/libclang_rt.builtins-x86_64.a
  --as-needed
  -lunwind
  --no-as-needed
  -lc
  /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root/lib/linux/libclang_rt.builtins-x86_64.a
  --as-needed
  -lunwind
  --no-as-needed
  /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root/lib/linux/clang_rt.crtend-x86_64.o
  /nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib/crtn.o
extra flags after to /nix/store/d6ini38wpv8f7ikkzj9bm15fqarfx9q5-llvm-binutils-16.0.6/bin/ld.lld:
  -rpath
  /nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib
ld.lld: error: unable to find library -lunwind
ld.lld: error: unable to find library -lunwind
clang-16: error: linker command failed with exit code 1 (use -v to see invocation)

How do I get the commit of my nixpkgs? I tried sudo nix-channel --update and it still doesn't work.

[AregevDev]

I'm having the same issue with llvmPackages, both 16 and 17. I am using WSL2

[nixos@nixos:~]$ NIX_DEBUG=1 clang -fuse-ld=lld -v main.c
HARDENING: disabled flags: pie pic format stackprotector fortify strictoverflow
extra flags before to /nix/store/pw7xsl0b4g7izz8hq2s5zkying2i7a4g-clang-16.0.6/bin/clang:
  -Wl\,-dynamic-linker=/nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib/ld-linux-x86-64.so.2
  -target
  x86_64-unknown-linux-gnu
original flags to /nix/store/pw7xsl0b4g7izz8hq2s5zkying2i7a4g-clang-16.0.6/bin/clang:
  -fuse-ld=lld
  -v
  main.c
extra flags after to /nix/store/pw7xsl0b4g7izz8hq2s5zkying2i7a4g-clang-16.0.6/bin/clang:
  -B/nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib/
  -idirafter
  /nix/store/zzwrkd2n3blr2m5ydm6236kbisvldj73-glibc-2.38-44-dev/include
  --gcc-toolchain=/nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0
  -B/nix/store/nzfgg5hbc3v4qisqj0ah9wdrbfszgfin-clang-16.0.6-lib/lib
  -resource-dir=/nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root
  -rtlib=compiler-rt
  -Wno-unused-command-line-argument
  -B/nix/store/8yp6irxxi36xqdfshbqgssv37zcplafy-compiler-rt-libc-16.0.6/lib
  --unwindlib=libunwind
  -B/nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/bin/
  -L/nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib
  -L/nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0//lib
  -L/nix/store/l0ydz31lwa97zickpsxj2vmprcigh1m4-gcc-12.3.0-libgcc/lib
  -L/nix/store/nzfgg5hbc3v4qisqj0ah9wdrbfszgfin-clang-16.0.6-lib/lib
clang version 16.0.6
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /nix/store/pw7xsl0b4g7izz8hq2s5zkying2i7a4g-clang-16.0.6/bin
Found candidate GCC installation: /nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0/lib/gcc/x86_64-unknown-linux-gnu/12.3.0
Found candidate GCC installation: /nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0/lib64/gcc/x86_64-unknown-linux-gnu/12.3.0
Selected GCC installation: /nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0/lib64/gcc/x86_64-unknown-linux-gnu/12.3.0
Candidate multilib: .;@m64
Selected multilib: .;@m64
 "/nix/store/pw7xsl0b4g7izz8hq2s5zkying2i7a4g-clang-16.0.6/bin/clang-16" -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name main.c -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=all -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -mllvm -treat-scalable-fixed-error-as-warning -debugger-tuning=gdb -v -fcoverage-compilation-dir=/home/nixos -nostdsysteminc -resource-dir /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root -idirafter /nix/store/zzwrkd2n3blr2m5ydm6236kbisvldj73-glibc-2.38-44-dev/include -internal-isystem /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root/include -Wno-unused-command-line-argument -fdebug-compilation-dir=/home/nixos -ferror-limit 19 -fgnuc-version=4.2.1 -fcolor-diagnostics -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/main-2c50d0.o -x c main.c
clang -cc1 version 16.0.6 based upon LLVM 16.0.6 default target x86_64-unknown-linux-gnu
#include "..." search starts here:
#include <...> search starts here:
 /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root/include
 /nix/store/zzwrkd2n3blr2m5ydm6236kbisvldj73-glibc-2.38-44-dev/include
End of search list.
 "/run/current-system/sw/bin/ld.lld" -pie --hash-style=gnu --eh-frame-hdr -m elf_x86_64 -o a.out /nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib/Scrt1.o /nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib/crti.o /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root/lib/linux/clang_rt.crtbegin-x86_64.o -L/nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib -L/nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0//lib -L/nix/store/l0ydz31lwa97zickpsxj2vmprcigh1m4-gcc-12.3.0-libgcc/lib -L/nix/store/nzfgg5hbc3v4qisqj0ah9wdrbfszgfin-clang-16.0.6-lib/lib -L/nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0/lib64/gcc/x86_64-unknown-linux-gnu/12.3.0 -L/nix/store/fdiknsmnnczx6brsbppyljcs9hqckawk-gcc-12.3.0/lib64/gcc/x86_64-unknown-linux-gnu/12.3.0/../../../../lib64 -L/lib -L/usr/lib -dynamic-linker=/nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib/ld-linux-x86-64.so.2 /tmp/main-2c50d0.o /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root/lib/linux/libclang_rt.builtins-x86_64.a --as-needed -lunwind --no-as-needed -lc /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root/lib/linux/libclang_rt.builtins-x86_64.a --as-needed -lunwind --no-as-needed /nix/store/32wbjm8xlndqkgx4rnk3r699aj8kcfn2-clang-wrapper-16.0.6/resource-root/lib/linux/clang_rt.crtend-x86_64.o /nix/store/1zy01hjzwvvia6h9dq5xar88v77fgh9x-glibc-2.38-44/lib/crtn.o
ld.lld: error: unable to find library -lunwind
ld.lld: error: unable to find library -lunwind
clang-16: error: linker command failed with exit code 1 (use -v to see invocation)

Seems like the libunwind isn't included in the library search paths

[AregevDev]

No matter what LLVM package version I use, there's no -L flag to libunwind's location. Manually adding it to the /nix/store location works ofc.

[pwaller]

Hey folks, I believe this was fixed in 555c7d1 as @SharzyL was suggesting. At least, I cannot reproduce here on my x86_64-linux. Prior to that commit I get the error you report building a test.c, after that commit, using clang to build something works.

You can test a specific nixpkgs commit using this command, which reports an error (or doesn't show libunwind) if there is an issue.

$ nix eval --json nixpkgs/555c7d1ba153b738356518ab1cfce4342582c3e5#llvmPackages_17.clangUseLLVM.nixSupport.cc-ldflags
["-L/nix/store/w3fpiryzpl7gdfskr754c5gkk3sm8qki-libunwind-17.0.6/lib"]

I think this can be closed, or at least it needs more information about what is being tested precisely (nixpkgs commit in particular).