I've found boost.system to be very useful for wrapping return codes from 3rd party libraries (e.g. libcurl). However, one problem I've encountered is that error_code's operator for boolean tests assumes that an error value of 0 == success. I've found it puzzling that this logic doesn't reside in the error_category, where it can be customized as needed. For instance, boolean tests could chain to a is_error() virtual method in the error_category, the default implementation of which preserves the current behavior: namespace boost { namespace system { class error_category : public noncopyable { public: // ... virtual bool is_error( int ev ) const { return ev != 0; } // ... }; class error_code { public: // ... operator unspecified-bool-type() const { return m_cat->is_error( m_val ) ? unspecified_bool_true : 0; } // ... }; } } Is there any reason this was not done? What do people think about adding it in a future release? Matt