Undefined symbols for architecture arm64 after nix upgrade

[Anton-4]

This issue is not encountered on main but does happen when upgrading to a newer nix revision.

This error only happens when building the tests $ cargo test --release --no-run, not when doing cargo build --release, building/running roc files, nor when using the repl.
Partial error:

[...]
error: could not compile `roc_repl_expect` (lib test) due to previous error
error: linking with `cc` failed: exit status: 1
  |
  = note: LC_ALL="C" PATH="/nix/store/k8ipha35ighvhbigcxh906fylq1w2c5a-rust-default-1.71.1/lib/rustlib/aarch64-apple-darwin/bin:[...]-dead_strip" "-nodefaultlibs"
  = note: Undefined symbols for architecture arm64:
            "std::terminate()", referenced from:
                llvm::itanium_demangle::Node::printAsOperand(llvm::itanium_demangle::OutputBuffer&, llvm::itanium_demangle::Node::Prec, bool) const in libllvm_sys-a632a77be37a2bc1.rlib(ItaniumDemangle.cpp.o)
                llvm::itanium_demangle::PODSmallVector<llvm::itanium_demangle::Node*, 32ul>::push_back(llvm::itanium_demangle::Node* const&) in libllvm_sys-a632a77be37a2bc1.rlib(ItaniumDemangle.cpp.o)
                llvm::itanium_demangle::SpecialName::printLeft(llvm::itanium_demangle::OutputBuffer&) const in libllvm_sys-a632a77be37a2bc1.rlib(ItaniumDemangle.cpp.o)
                llvm::itanium_demangle::CtorVtableSpecialName::printLeft(llvm::itanium_demangle::OutputBuffer&) const in libllvm_sys-a632a77be37a2bc1.rlib(ItaniumDemangle.cpp.o)
                llvm::itanium_demangle::NameType::printLeft(llvm::itanium_demangle::OutputBuffer&) const in libllvm_sys-a632a77be37a2bc1.rlib(ItaniumDemangle.cpp.o)
                llvm::itanium_demangle::ModuleName::printLeft(llvm::itanium_demangle::OutputBuffer&) const in libllvm_sys-a632a77be37a2bc1.rlib(ItaniumDemangle.cpp.o)
                llvm::itanium_demangle::PODSmallVector<llvm::itanium_demangle::PODSmallVector<llvm::itanium_demangle::Node*, 8ul>*, 4ul>::push_back(llvm::itanium_demangle::PODSmallVector<llvm::itanium_demangle::Node*, 8ul>* const&) in libllvm_sys-a632a77be37a2bc1.rlib(ItaniumDemangle.cpp.o)
                ...
[...]
            "operator new(unsigned long)", referenced from:
                _LLVMContextCreate in libllvm_sys-a632a77be37a2bc1.rlib(Core.cpp.o)
                llvm::Module::setModuleInlineAsm(llvm::StringRef) in libllvm_sys-a632a77be37a2bc1.rlib(Core.cpp.o)
                _LLVMAppendBasicBlockInContext in libllvm_sys-a632a77be37a2bc1.rlib(Core.cpp.o)
                _LLVMCreateBuilderInContext in libllvm_sys-a632a77be37a2bc1.rlib(Core.cpp.o)
                _LLVMCreatePassManager in libllvm_sys-a632a77be37a2bc1.rlib(Core.cpp.o)
                _LLVMCreateFunctionPassManagerForModule in libllvm_sys-a632a77be37a2bc1.rlib(Core.cpp.o)
                std::__1::vector<llvm::GenericValue, std::__1::allocator<llvm::GenericValue>>::reserve(unsigned long) in libllvm_sys-a632a77be37a2bc1.rlib(ExecutionEngineBindings.cpp.o)
                ...
          ld: symbol(s) not found for architecture arm64
          clang-16: error: linker command failed with exit code 1 (use -v to see invocation)
          

error: could not compile `test_gen` (test "test_gen") due to previous error
Undefined symbols

I was able to bisect this to nixpkgs commit bcbdb800cf7659d6ff36ac114121a056fe8c9656
.

This commit updates llvmPackages on Darwin from 11 to 16. I'm not yet sure why this change is resulting in the Undefined symbols for architecture arm64. The fact that this is only happening when building tests is probably a valuable clue.

[Anton-4]

Looks like this was caused by NixOS/nixpkgs#166205.

Workarounds are available, going to try them out now.

[Anton-4]

Running with RUSTFLAGS="-C link-arg=-lc++abi" fixes the issue. I'm going to update the shellHook in the flake to:

shellHook = ''
            export LLVM_SYS_${llvmMajorMinorStr}_PREFIX="${llvmPkgs.llvm.dev}"
            ${aliases}
            '' + lib.optionalString (system == "aarch64-darwin") ''
              export RUSTFLAGS="-C link-arg=-lc++abi"
            ''; # lc++abi as workaround for github.com/NixOS/nixpkgs/issues/166205, see also github.com/roc-lang/roc/issues/6303