"Unused function" build failure(s) — clang 3.4.2

-Wall -Werror are including the option -Wunused-function. Without not the case with g++
namespace { 
   void dummy_for_semicolon_do_not_use();
}
PackageVersionSupposed error messageFull log Bug report
cdebootstrap 0.5.10../../../../src/frontend/standalone/message.c:79:12: error: unused function 'unused' [-Werror,-Wunused-function] Log 751630
criu 1.3~rc1-1arch/x86/crtools.c:35:20: error: unused function '__check_code_syscall' [-Werror,-Wunused-function] Log 753845
writerperfect 0.8.4-3FemtoZip.cxx:135:30: error: unused function 'hash' [-Werror,-Wunused-function] Log 751906

3 errors