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The GNU C Library

A.2.2 How Variadic Functions are Defined and Used

Defining and using a variadic function involves three steps:

• Define the function as variadic, using an ellipsis (`...') in the argument list, and using special macros to access the variable arguments. See section A.2.2.2 Receiving the Argument Values.

• Declare the function as variadic, using a prototype with an ellipsis (`...'), in all the files which call it. See section A.2.2.1 Syntax for Variable Arguments.

• Call the function by writing the fixed arguments followed by the additional variable arguments. See section A.2.2.4 Calling Variadic Functions.

A.2.2.1 Syntax for Variable Arguments		How to make a prototype for a function with variable arguments.
A.2.2.2 Receiving the Argument Values		Steps you must follow to access the optional argument values.
A.2.2.3 How Many Arguments Were Supplied		How to decide whether there are more arguments.
A.2.2.4 Calling Variadic Functions		Things you need to know about calling variable arguments functions.
A.2.2.5 Argument Access Macros		Detailed specification of the macros for accessing variable arguments.
A.2.3.1 Old-Style Variadic Functions		The pre-ISO way of defining variadic functions.