Neal Becker wrote:

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

What are the symbols? Are they gthread_xxx and weak pthread_xxx symbols? libstdc++ uses gthreads, which is an abstraction over pthreads. In the libstdc++ library there are weak symbols for some pthreads symbols which are just empty stubs. Unless -pthreads is given then the empty stubs will be used (so it's not really doing anything like creating threads or locking mutexes). If -pthreads is used the real pthreads symbols will override the weak symbols and provide the real threading support. I would expect to see something like the following in a non-threaded binary that uses libstdc++: 080712f4 t __gthread_active_p() 0806a194 t __gthread_active_p() 08049dc4 t __gthread_active_p() 080699bc T std::__basic_file<char>::__basic_file(pthread_mutex**) 080699a8 T std::__basic_file<char>::__basic_file(pthread_mutex**) 0808ef34 d __gthread_active_p()::__gthread_active_ptr 0808f10c d __gthread_active_p()::__gthread_active_ptr 08088c90 r __gthread_active_p()::__gthread_active_ptr 08078eb4 T __error_unthreaded 08090944 D __isthreaded w pthread_cancel w pthread_getspecific w pthread_key_create w pthread_mutex_lock w pthread_mutex_unlock w pthread_once w pthread_setspecific 0808ef30 d use_thread_key jon -- Horms and I discussed this, and we came up with two categories of people. People who use vim, and people who don't realize that they could be using vim. - Geoff Harrison