Let's say someone writes a totally awesome object-oriented library in C++. Someone else would like to make pascal headers for this, but how? Pascal classes and C++ classes aren't compatible.
There is a interesting article about how to use C++ clases into delphi,

http://www.rvelthuis.de/articles/articles-cppobjs.html

But its is always required a DLL as Delphi's linker cant link c++ .OBJ.