Tyng-Ruey Chuang, Y. S. Kuo and Chien-Min Wang
We describe the design and implementation of system architecture to support object introspection in C++. An introspective object permits observation and change to its own state by a general mechanism that is applicable to objects of all classes. This general mechanism allows the construction of applications where objects are late-binding and the interactions between them are highly dynamic.
Unlike Java, which provides full support for object introspection, C++ has limited built-in introspective capability via its Run-Time Type Information (RTTI) and related facilities. For example, in C++ one cannot query an object for methods that can be applied to it. We show how such introspective information can be collected at compile-time by parsing class declarations, and be used to build a supporting environment for object introspection at run-time.
Our approach is non-intrusive because it requires no change to the original class declarations and libraries, and it guarantees compatibility between objects before and after the addition of introspective capability. This is important if one wants to integrate third-party class libraries, which are often supplied as black boxes and allow no modification, into highly dynamic applications. We show two applications that are built on top of our introspective environment. The first is a generic facility for automatic I/O support of complex C++ objects. The other is a class exerciser that allows interactive execution of dynamically loaded C++ class libraries.