Hello, On ubuntu, I have a piece of software linking against the boost thread library. Linking with boost version 1.40 I don't have any problem, whereas switching to 1.41 I got the undefined reference to `boost::thread_resource_error::thread_resource_error()' In the sources I see that this constructor is now inlined and if I do nm -C -D libboost_thread.so | grep thread_resource_error from this (1.40) 0000ee80 T boost::thread_resource_error::thread_resource_error(int) 0000ee00 T boost::thread_resource_error::thread_resource_error() 0000ee40 T boost::thread_resource_error::thread_resource_error(int) 0000edc0 T boost::thread_resource_error::thread_resource_error() 0000f4c0 T boost::thread_resource_error::~thread_resource_error() 0000f500 T boost::thread_resource_error::~thread_resource_error() 0000f530 T boost::thread_resource_error::~thread_resource_error() 0000eec0 T boost::thread_resource_error::what() const 00013e00 V typeinfo for boost::thread_resource_error 0000ffc0 V typeinfo name for boost::thread_resource_error 00013d98 V vtable for boost::thread_resource_error I got this (1.41) 0000b6e0 W boost::thread_resource_error::~thread_resource_error() 0000b720 W boost::thread_resource_error::~thread_resource_error() 0000b480 W boost::thread_resource_error::what() const 0001282c V typeinfo for boost::thread_resource_error 0000ed00 V typeinfo name for boost::thread_resource_error 00012848 V vtable for boost::thread_resource_error The symbol is weak now. I should be not a problem, right? But I got the unresolved ref What is the best option to have my stuff compiled without the unresolved refs? Thanks Stefano