GCC Extensions

The CodeWarrior compiler accepts many of the extensions to the C language that the GCC (Gnu Compiler Collection) tools allow. Source code that uses these extensions does not conform to the ISO/IEC 9899-1990 C ("C90") standard.

• Controlling GCC Extensions
  Controlling GCC extensions to the C language.
• Initializing Automatic Arrays and Structures
  When the GCC extensions setting is on, array and structure variables that are local to a function and have the automatic storage class may be initialized with values that do not need to be constant.
• The sizeof() Operator
  When the GCC extensions setting is on, the sizeof() operator computes the size of function and void types. In both cases, the sizeof() operator evaluates to 1.
• Statements in Expressions
  When the GCC extensions setting is on, expressions in function bodies may contain statements and definitions.
• Redefining Macros
  When the GCC extensions setting is on, macros may be redefined with the #define directive without first undefining them with the #undef directive.
• The typeof() Operator
  When the GCC extensions setting is on, the compiler recognizes the typeof() operator. This compile-time operator returns the type of an expression.
• Void and Function Pointer Arithmetic
  The ISO/IEC 9899-1990 C Standard does not accept arithmetic expressions that use pointers to void or functions. With GCC extensions on, the compiler accepts arithmetic manipulation of pointers to void and functions.
• The __builtin_constant_p() Operator
  When the GCC extensions setting is on, the compiler recognizes the __builtin_constant_p() operator. This compile-time operator takes a single argument and returns 1 if the argument is a constant expression or 0 if it is not.
• Forward Declarations of Static Arrays
  When the GCC extensions setting is on, the compiler will not issue an error when you declare a static array without specifying the number of elements in the array if you later declare the array completely.
• Omitted Operands in Conditional Expressions
  When the GCC extensions setting is on, you may skip the second expression in a conditional expression.
• The __builtin_expect() Operator
  When the GCC extensions setting is on, the compiler recognizes the __builtin_expect() operator.
• Void Return Statements
  When the GCC extensions setting is on, the compiler allows you to place expressions of type void in a return statement.
• Minimum and Maximum Operators
  When the GCC extensions setting is on, the compiler recognizes built-in minimum ( <? ) and maximum ( >? ) operators.
• Local Labels
  When the GCC extensions setting is on, the compiler allows labels limited to a block's scope.