Early in 2003, Bill Wallace contributed a patch which makes it practical [with which version?] to write
critcl::config language c++
But what's the point? Since Critcl is at its best coding tiny bits of what inventor JCW calls "grease", what's the advantage of C++ over C? A concrete example will probably be instructive ...
I would presume that the point is that many applications, especially on Windows, export APIs that are accessible only from C++; if you're using Critcl to build a Tcl interface to one of them, you'll need something like this.