The GNU compiler provides these extensions to the C++ language (and you can also use most of the C language extensions in your C++ programs). If you want to write code that checks whether these features are available, you can test for the GNU compiler the same way as for C programs: check for a predefined macro __GNUC__ . You can also use __GNUG__ to test specifically for GNU C++ (see Standard Predefined Macros).
| Naming Results | Giving a name to C++ function return values. |
| Min and Max | C++ Minimum and maximum operators. |
| Destructors and Goto | Goto is safe to use in C++ even when destructors are needed. |
| C++ Interface | You can use a single C++ header file for both declarations and definitions. |
| Template Instantiation | Methods for ensuring that exactly one copy of each needed template instantiation is emitted. |
| C++ Signatures | You can specify abstract types to get subtype polymorphism independent from inheritance. |