Variadic functions

< cpp‎ | utility

Variadic functions are functions (e.g. std::printf) which take a variable number of arguments.

To declare a variadic function, an ellipsis is used as the last parameter, e.g. int printf(const char* format, ...);. See Variadic arguments for additional detail on the syntax, automatic argument conversions and the alternatives.

To access the variadic arguments from the function body, the following library facilities are provided:

Defined in header <cstdarg>
enables access to variadic function arguments
(function macro)
accesses the next variadic function argument
(function macro)
makes a copy of the variadic function arguments
(function macro)
ends traversal of the variadic function arguments
(function macro)
holds the information needed by va_start, va_arg, va_end, and va_copy

[edit] Example

#include <iostream>
#include <cstdarg>
void simple_printf(const char* fmt...)
    va_list args;
    va_start(args, fmt);
    while (*fmt != '\0') {
        if (*fmt == 'd') {
            int i = va_arg(args, int);
            std::cout << i << '\n';
        } else if (*fmt == 'c') {
            // note automatic conversion to integral type
            int c = va_arg(args, int);
            std::cout << static_cast<char>(c) << '\n';
        } else if (*fmt == 'f') {
            double d = va_arg(args, double);
            std::cout << d << '\n';
int main()
    simple_printf("dcff", 3, 'a', 1.999, 42.5); 



[edit] See also

C documentation for Variadic functions