We further explore this particularly interesting challenge because it is also relevant to the glibc + LLVM users or distributions: boostrapping glibc with an LLVM toolchain. glibc -> compiler-rt -> glibc glibc -> llvm-libunwind -> glibc compiler-rt -> libxcrypt -> glibc -> compiler-rt compiler-rt -> libcxx -> llvm-libunwind -> glibc -> compiler-rt We have reached a point where the ChromiumOS test suites pass, but the LLVM builds are intentionally not enabled by default (the glibc llvm USE flag is disabled), because some compromises have been made like the previously-mentioned disabling of thumb mode for ARM builds.