Compilation Issue with Symbols

[Dhruv-Trivedi]

Hello there!

I know this is not the best place to share my error, but I've been trying to compile XNU via this script and I'm stuck at a specific point — ld cannot load symbols for any architecture that I try to compile for. I've tried the build on an iMac Pro and an M1 MacBook Pro (T8103), both running macOS Sequoia 15.4.

Some articles that I came across indicate that I might be invoking clang++ for .c files, which results in a symbol resolution error — checking the build log, this is what I came across when running the recommended MACOS_VERSION='15.0' KERNEL_CONFIG=RELEASE ARCH_CONFIG=ARM64 MACHINE_CONFIG=VMAPPLE ./build.sh --clean --kc build command:

LDFILELIST bsd
CC lastkerneldataconst.o
CC lastkernelconstructor.o
CC nonlto.o
CC version.o
LD kernel.release.vmapple.unstripped.noctf

This last call to LD is invoking clang++ from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++, and this is the resultant error:

Undefined symbols for architecture arm64e:
  "OSValueObject<int>::MetaClass::MetaClass()", referenced from:
      ___cxx_global_var_init in OSValueObject.cpo
ld: symbol(s) not found for architecture arm64e
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
make[3]: *** [${BUILD_DIR}/build/xnu.obj/RELEASE_ARM64_VMAPPLE//kernel.release.vmapple.unstripped.noctf] Error 1
make[2]: *** [build_all] Error 2
make[1]: *** [build_all_bootstrap_RELEASE^ARM64^VMAPPLE] Error 2
make: *** [install] Error 2

Am I missing a cross-compiler toolchain? I am very new to XNU and the build process, but am hoping to learn. Thank you!