[boost] Confused about threading

I started out by trying to figure out if shared_ptr always uses threading. A quick look at the jamfiles did not suggest that threading was disabled when building single. Then I tried this: nm --demangle libboost_regex-d.a | grep -i thread [ lots of threading symbols ] OK, so why is the single threaded version of a library full of threading references? Is this a problem? Oh, this is gcc/linux system