Describes the language extensions that the compiler supports.
It contains the following:
9.1 Preprocessor extensions.
9.2 #assert.
9.3 #include_next.
9.4 #unassert.
9.5 #warning.
9.6 C99 language features available in C90.
9.7 // comments.
9.8 Subscripting struct.
9.9 Flexible array members.
9.10 C99 language features available in C++ and C90.
9.11 Variadic macros.
9.12 long long.
9.13 restrict.
9.14 Hexadecimal floats.
9.15 Standard C language extensions.
9.16 Constant expressions.
9.17 Array and pointer extensions.
9.18 Block scope function declarations.
9.19 Dollar signs in identifiers.
9.20 Top-level declarations.
9.21 Benign redeclarations.
9.22 External entities.
9.23 Function prototypes.
9.24 Standard C++ language extensions.
9.25 ? operator.
9.26 Declaration of a class member.
9.27 friend.
9.28 Read/write constants.
9.29 Scalar type constants.
9.30 Specialization of nonmember function templates.
9.31 Type conversions.
9.32 Standard C and Standard C++ language extensions.
9.33 Address of a register variable.
9.34 Arguments to functions.
9.35 Anonymous classes, structures and unions.
9.36 Assembler labels.
9.37 Empty declaration.
9.38 Hexadecimal floating-point constants.
9.39 Incomplete enums.
9.40 Integral type extensions.
9.41 Label definitions.
9.42 Long float.
9.43 Nonstatic local variables.
9.44 Structure, union, enum, and bitfield extensions.
9.45 GNU extensions to the C and C++ languages.