noexcept actually forces it, if it doesn’t know it must essentially wrap the function body in a try { …body… } catch(…) { terminate( ); }. So the compiler is do

noexcept actually forces it, if it doesn’t know it must essentially wrap the function body in a try { …body… } catch(…) { terminate( ); }. So the compiler is doing the same amount of work inside the function. Outside it can assume that no exception will escape that function, yes. If it knows, it doesn’t need to.