Using a dual library, as CXXD does, means that a programmer should have knowledge of any differences which may exist between the Boost implementation of a dual library and the C++ standard implementation of that same dual library.

There are a number of areas for the programmer to consider when using a particular dual library:

All of the above are valid concerns. I have had expressed to me that using CXXD is not a valid choice to use because it masks the issues I bring up above. I can understand that point of view. Furthermore I have had it expressed to me that CXXD should somehow document any differences between the implementation of the Boost library and the C++ standard library for each of the dual libraries supported. Again this is a valid point of view, but I do not think the CXXD library is the place for such documentation.

The design of CXXD is that the advantages of being able to offer to the programmer the choice of using either the Boost implementation or the C++ standard implementation of a dual library, while using both with the same code, offsets the issues above and the concerns of others in using CXXD in the designer's mind. But I am aware of the issues and concerns stated above and want to mention them here in the documentation to CXXD.

The issues and concerns are very much the same whenever a particular implementation of any library is chosen, whether that library is a Boost library, a C++ standard library, or a 3rd party library. That each mod really involves two different implementations, or libraries if you will, is something I have made plain in the documentation, and I want to reiterate it here. Knowledge of those libraries, for any particular mod, is still of first importance in programming using CXXD. Essentially CXXD is a framework for supporting dual libraries, but it is not an excuse for not understanding the functionality of a particular dual library in the first place.

Although I have done so in other areas of the documentation I would like to again emphasize the importance of documenting when a dual library is being used by the end-user. This is especially true when CXXD is being used in a third party library, whether that library is a header-only library or non-header only library where some part of the library is being built into a shared or static library. Without documenting that a particular dual library is being used a programmer cannot know, depending on the compiler implementation and the compiler's command line parameters, that either the Boost implementation or the C++ standard implementation of the dual library is being used in the code.