Compiler warning when building Tor under clang/LLVM

With Git master (26009a3), building Tor under clang generates a compiler warning:

rendclient.c:407:3: warning: expression result unused [-Wunused-value] (int) hid_serv_get_responsible_directories(responsible_dirs, desc_id);

I presume the problem is the int cast, but it seems to do nothing so is there a reason to include it in the first place?