Hi I'm trying to use boost::signal to replace a library of my own It compiles well but at runtime It raises an exception on the following line boost::signal<> sig; the exception is raised in function_template.hpp template< typename FunctionObj, typename R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_PARMS > struct BOOST_FUNCTION_FUNCTION_OBJ_INVOKER { static R invoke(function_buffer& function_obj_ptr BOOST_FUNCTION_COMMA BOOST_FUNCTION_PARMS) { FunctionObj* f; if (function_allows_small_object_optimization<FunctionObj>::value) f = reinterpret_cast(&function_obj_ptr.data); else f = reinterpret_cast(function_obj_ptr.obj_ptr); return (*f)(BOOST_FUNCTION_ARGS); <<<<< exception raised here } }; Does the sig have to be initialized in a specific way ???