[Boost-users] How to detect overflow when use lexical_cast??

Hi,all I want to cast string to long long type and handle overflow. I tested as follow. long long somevar = lexical_cast<long long>("123456789789789798879977978789787987879879787977897897897899879978798798798");//!!!!!!!!!!!!!! But it does not throw an exception!! It seem that casting to int does not have this kind of problem. int somevar2 = lexical_cast<int>("123456789789789798879977978789787987879");//will throw an exception