"Old Boost" is based on pre-C++11, so it has to use inefficient tricks to emulate features that don't yet exist in pre-C++11 compilers. "New boost" is in process of C++11-modernization and modularization, not complete yet. https://github.com/boostorg 真怕 binary bloat 的话,可以用 objdump 看看 bloat 在什么地方。