The Free Software Foundation and GCC Steering Committee have now decided that it's okay and permitted to write code for the GNU Compiler Collection (GCC) within C++. Up to this point, C has been the preferred language for working on GCC.
While C++ can now be used within GCC, it's still to be decided what C++ features the developers can use within the language when working on this free software compiler. C++98 is the expected standard that will be allowed within the GCC code-base, but the programming language's features and libraries are still being decided on amongst developers.
This announcement that C++ can now be used in GCC itself can be found on the GCC mailing list