| g++ is the Free Software Foundation's C++ compiler. g++ is a frontend of the gcc system---as such, it uses the same backend, including optimisation, as does the C compiler. Of course, some
C++ features, such as templates, exceptions, and virtual member functions, will result in executable bloat or slowdown. But that's the price one pays for better abstraction.
g++ was, for a long time, significantly behind standard C++. However, since the development (and re-merge) of egcs, g++ has gotten much better in, for example, its support of templates,
the STL, namespaces, and exceptions. GNU libstdc++-v3, still in development, promises to provide even better STL support.
g++ is by no means considered the best C++ compiler out there. However, it is one of the best free ones, and certainly one of the most popular in the Unix world. | 
