[aarch64-pc-windows-gnullvm] Can't build simple test app, fails with `rust-lld: error: undefined symbol: __chkstk`

[ColinFinck]

I created a new test application using cargo new testapp.

Using nightly-2025-12-23-aarch64-pc-windows-gnullvm with

[target.aarch64-pc-windows-gnullvm]
linker = "rust-lld"

in my .cargo\config.toml, I try to build my application via cargo build.

I'm reproducibly getting the error:

   Compiling testapp v0.1.0 (C:\Users\Colin Finck\testapp)
error: linking with `rust-lld` failed: exit code: 1
  |
  = note: "rust-lld" "-flavor" "gnu" "-m" "arm64pe" "<sysroot>\\lib\\rustlib\\aarch64-pc-windows-gnullvm\\lib\\self-contained\\crt2.o" "C:\\Users\\COLINF~1\\AppData\\Local\\Temp\\rustc3UtMMj\\symbols.o" "<7 object files omitted>" "-Bstatic" "<sysroot>\\lib\\rustlib\\aarch64-pc-windows-gnullvm\\lib/{libstd-*,libpanic_unwind-*,libobject-*,libmemchr-*,libaddr2line-*,libgimli-*,libcfg_if-*,libwindows_targets-*,librustc_demangle-*,libstd_detect-*,libhashbrown-*,librustc_std_workspace_alloc-*,libminiz_oxide-*,libadler2-*,libunwind-*,liblibc-*,librustc_std_workspace_core-*,liballoc-*,libcore-*,libcompiler_builtins-*}.rlib" "-Bdynamic" "-lkernel32" "-lkernel32" "-lkernel32" "-lntdll" "-luserenv" "-lws2_32" "-ldbghelp" "-lunwind" "-lmingw32" "-lmingwex" "-lmsvcrt" "-lkernel32" "-luser32" "--nxcompat" "-L" "<sysroot>\\lib\\rustlib\\aarch64-pc-windows-gnullvm\\lib\\self-contained" "-o" "C:\\Users\\Colin Finck\\testapp\\target\\debug\\deps\\testapp-1ac80cd7427b48a6.exe" "--gc-sections"
  = note: some arguments are omitted. use `--verbose` to show all linker arguments
  = note: rust-lld: error: undefined symbol: __chkstk
          >>> referenced by /rustc/4f14395c37db4c1be874e6b0ace6721674223c22/library\std\src\sys/backtrace.rs:162
          >>>               libstd-51b3a38044c30c21.rlib(std-51b3a38044c30c21.std.17a6194c5b16bd2d-cgu.0.rcgu.o):(std::sys::backtrace::__rust_begin_short_backtrace::<std::sys::process::windows::child_pipe::spawn_pipe_relay::{closure#0}, ()>)
          >>> referenced by C:\a\rust\rust\library\core\src\slice\sort\stable/mod.rs:94
          >>>               libstd-51b3a38044c30c21.rlib(std-51b3a38044c30c21.std.17a6194c5b16bd2d-cgu.0.rcgu.o):(core::slice::sort::stable::driftsort_main::<addr2line::line::LineSequence, <[addr2line::line::LineSequence]>::sort_by_key<u64, <addr2line::line::Lines>::parse<gimli::read::endian_slice::EndianSlice<gimli::endianity::LittleEndian>>::{closure#1}>::{closure#0}, alloc::vec::Vec<addr2line::line::LineSequence>>)
          >>> referenced by C:\a\rust\rust\library\core\src\slice\sort\stable/mod.rs:94
          >>>               libstd-51b3a38044c30c21.rlib(std-51b3a38044c30c21.std.17a6194c5b16bd2d-cgu.0.rcgu.o):(core::slice::sort::stable::driftsort_main::<addr2line::unit::UnitRange, <[addr2line::unit::UnitRange]>::sort_by_key<u64, <addr2line::unit::ResUnits<gimli::read::endian_slice::EndianSlice<gimli::endianity::LittleEndian>>>::parse::{closure#4}>::{closure#0}, alloc::vec::Vec<addr2line::unit::UnitRange>>)
          >>> referenced 10 more times


error: could not compile `testapp` (bin "testapp") due to 1 previous error

This works fine for the x86_64-pc-windows-gnullvm target.

I've found similar bugs #57983 and #98254, but they deal with the aarch64-unknown-uefi target, not the aarch64-pc-windows-gnullvm one.

CC @mati865 (happy new year and thanks a lot for all your previous work on the gnullvm targets!)

[bjorn3]

Do you have the rust-mingw component installed?

[mati865]

__chkstk should be provided by compiler-builtins, similarly to x86_64, but it's not. I'll fix it soon.

[Fulgen301]

__chkstk isn't provided by compiler-builtins for x86_64, but the system one is used, which is in kernelbase.dll.

[mati865]

Sorry for that mental shortcut. To be exact, x86_64 uses ___chkstk_ms, but they do the same thing.
They all are provided by the compiler builtins:

$ nm -A /g/msys64/opt/llvm-mingw-20251216-ucrt-x86_64/lib/clang/21/lib/windows/libclang_rt.builtins-* | rg chkstk
G:/msys64/opt/llvm-mingw-20251216-ucrt-x86_64/lib/clang/21/lib/windows/libclang_rt.builtins-aarch64.a:chkstk.S.obj: 00000000 T #__chkstk_arm64ec
G:/msys64/opt/llvm-mingw-20251216-ucrt-x86_64/lib/clang/21/lib/windows/libclang_rt.builtins-aarch64.a:chkstk.S.obj: 00000000 T __chkstk
G:/msys64/opt/llvm-mingw-20251216-ucrt-x86_64/lib/clang/21/lib/windows/libclang_rt.builtins-arm.a:chkstk.S.obj: 00000000 T __chkstk
G:/msys64/opt/llvm-mingw-20251216-ucrt-x86_64/lib/clang/21/lib/windows/libclang_rt.builtins-i386.a:chkstk.S.obj: 00000000 T __alloca
G:/msys64/opt/llvm-mingw-20251216-ucrt-x86_64/lib/clang/21/lib/windows/libclang_rt.builtins-x86_64.a:chkstk.S.obj: 00000000 T ___chkstk_ms

As of mingw-w64/mingw-w64@5af8d91 it's no longer provided in mingw-w64 import libraries to avoid conflicts. So, the only source of that symbol with mingw-w64 is the compiler builtins.

[tgross35]

As of mingw-w64/mingw-w64@5af8d91 it's no longer provided in mingw-w64 import libraries to avoid conflicts. So, the only source of that symbol with mingw-w64 is the compiler builtins.

That patch was applied in 2020. Any idea why the problem is just showing up now?

[mati865]

@tgross35 it shows up only when linking with LLD directly. In that case Clang's compiler-rt is not added to the linker and it used to provide that symbol.