Gcc/10.2.0/gcc/C 002b 002b-Extensions

7 Extensions to the C++ Language

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 Predefined Macros in The GNU C Preprocessor).

• C++ Volatiles:		What constitutes an access to a volatile object.
• Restricted Pointers:		C99 restricted pointers and references.
• Vague Linkage:		Where G++ puts inlines, vtables and such.
• 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.
• Bound member functions:		You can extract a function pointer to the method denoted by a ‘`->`’ or ‘`.`’ expression.
• C++ Attributes:		Variable, function, and type attributes for C++ only.
• Function Multiversioning:		Declaring multiple function versions.
• Type Traits:		Compiler support for type traits.
• C++ Concepts:		Improved support for generic programming.
• Deprecated Features:		Things will disappear from G++.
• Backwards Compatibility:		Compatibilities with earlier definitions of C++.