Page History

Variadic functions accept a variable number of arguments but are problematic. Variadic functions define an implicit contract between the function writer and the function user that allows the function to determine the number of arguments passed in any particular invocation. Failure to enforce this contract may result in undefined behavior. See undefined behavior 141 of Appendix J of the C Standard [ISO/IEC 9899:2011].

Argument Processing

In the following code example, the variadic function average() calculates the average value of the positive integer arguments passed to the function [Seacord 2005c]. The function processes arguments until it encounters an argument with the value of va_eol (-1).

...

...